JP7338963B2 - Multilayer ceramic capacitors and ceramic raw material powders - Google Patents

Description

The present invention relates to a multilayer ceramic capacitor and ceramic raw material powder.

There is a demand for a dielectric material that provides sufficient reliability characteristics in a multilayer ceramic capacitor having a thin dielectric layer. For example, it has been found effective to dissolve a specific element in the raw material powder in advance. Patent Literature 1 discloses a technique of adding a donor element for the purpose of improving life characteristics.

JP 2016-139720 A

However, in recent years when the thickness of the dielectric layer is small and the number of laminated layers is increasing, there is a demand for further improvement in life characteristics. There is also a demand for improved insulating properties. Therefore, it is difficult to achieve higher reliability only with the technique of reducing the amount of oxygen defects using a donor element.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a multilayer ceramic capacitor and a ceramic raw material powder that can achieve high reliability.

A multilayer ceramic capacitor according to the present invention includes a laminate in which dielectric layers and internal electrode layers are alternately laminated, and the main component of the dielectric layers is a perovskite structure represented by the general formula _ABO3 . and the B site contains an element that functions as a donor, and both the A site and the B site are a ceramic material containing a rare earth element , the ceramic material contains Ba and Ti, and the A site and the B site include: The same kind of rare earth element is dissolved in solid solution, and the rare earth element contained in the A site includes at least one of La, Ce, Pr, Nd, Pm, Sm, Eu and Gd, and is contained in the B site. The rare earth element contains at least one of Er, Tm, and Yb, and the solid solution amount of the rare earth element solid-dissolved at the A site (A-site solid-solution amount) and the solid-solution amount of the rare earth element solid-dissolved at the B site are The ratio to the solid solution amount (B site solid solution amount) is characterized by satisfying 0.75≦(A site solid solution amount/B site solid solution amount)≦1.25.

In the above multilayer ceramic capacitor, the ceramic material may contain Ba and Ti.

In the above multilayer ceramic capacitor, the element functioning as the donor may contain Mo.

In the multilayer ceramic capacitor described above, the rare earth element may include at least one of Tb, Dy, Ho and Y.

In the multilayer ceramic capacitor, the rare earth element contained in the A site includes at least one of La, Ce, Pr, Nd, Pm, Sm, Eu and Gd, and the rare earth element contained in the B site is At least one of Er, Tm and Yb may be included.

In the laminated ceramic capacitor, the thickness of the dielectric layer in the lamination direction may be 0.4 μm or less.

In the multilayer ceramic capacitor, the solid solution amount of the rare earth element dissolved in the A site (A site solid solution amount) and the solid solution amount of the rare earth element solid dissolved in the B site (B site solid solution amount) may satisfy 0.95≦(A-site solid-solution amount/B-site solid-solution amount)≦1.05.

The ceramic raw material powder according to the present invention is a ceramic raw material powder containing Ba and Ti, having a perovskite structure represented by the general formula _ABO3 as a main phase, containing an element functioning as a donor at the B site, and All of the B sites contain a rare earth element, the same kind of rare earth element is dissolved in the A site and the B site , and the rare earth elements contained in the A site are La, Ce, Pr, Nd, and Pm. , Sm, Eu and Gd, the rare earth element contained in the B site contains at least one of Er, Tm and Yb, and the solid solution amount of the rare earth element dissolved in the A site The ratio between (A-site solid-solution amount) and the solid-solution amount of the rare earth element solid-soluted in the B-site (B-site solid-solution amount) is 0.75 ≤ (A-site solid-solution amount/B-site solid-solution amount )≦1.25.

The ceramic raw material powder may contain Ba and Ti.

In the ceramic raw material powder, the element functioning as the donor may contain Mo.

In the ceramic raw material powder, the rare earth element may include at least one of Tb, Dy, Ho and Y.

In the ceramic raw material powder, the rare earth element contained in the A site includes at least one of La, Ce, Pr, Nd, Pm, Sm, Eu and Gd, and the rare earth element contained in the B site is At least one of Er, Tm and Yb may be included.

In the ceramic raw material powder, the solid solution amount of the rare earth element dissolved in the A site (A site solid solution amount) and the solid solution amount of the rare earth element solid dissolved in the B site (B site solid solution amount) may satisfy 0.95≦(A-site solid-solution amount/B-site solid-solution amount)≦1.05.
In the above laminated ceramic capacitor, Ho may be dissolved in the A site and the B site.
In the ceramic raw material powder, Ho may be dissolved in the A site and the B site.

According to the present invention, it is possible to provide a multilayer ceramic capacitor and a ceramic raw material powder that can achieve high reliability.

1 is a partial cross-sectional perspective view of a laminated ceramic capacitor; FIG. It is a figure which illustrates the flow of the manufacturing method of a laminated ceramic capacitor. FIG. 5 is a diagram showing test results of Examples and Comparative Examples.

Hereinafter, embodiments will be described with reference to the drawings.

(embodiment)
FIG. 1 is a partial cross-sectional perspective view of a laminated ceramic capacitor 100 according to an embodiment. As illustrated in FIG. 1, a multilayer ceramic capacitor 100 includes a multilayer chip 10 having a substantially rectangular parallelepiped shape, and external electrodes 20a and 20b provided on either of two opposing end surfaces of the multilayer chip 10. As shown in FIG. Of the four surfaces of the laminated chip 10 other than the two end surfaces, two surfaces other than the top surface and the bottom surface in the stacking direction are referred to as side surfaces. The external electrodes 20a and 20b extend on the upper surface, lower surface and two side surfaces of the laminated chip 10 in the lamination direction. However, the external electrodes 20a and 20b are separated from each other.

The laminated chip 10 has a laminate structure in which dielectric layers 11 containing a ceramic material functioning as a dielectric and internal electrode layers 12 containing a base metal material are alternately laminated. The edge of each internal electrode layer 12 is alternately exposed to the end face provided with the external electrode 20a of the laminated chip 10 and the end face provided with the external electrode 20b. Thereby, each internal electrode layer 12 is alternately connected to the external electrode 20a and the external electrode 20b. As a result, the multilayer ceramic capacitor 100 has a configuration in which a plurality of dielectric layers 11 are laminated with internal electrode layers 12 interposed therebetween. In the laminated body of the dielectric layers 11 and the internal electrode layers 12 , the internal electrode layer 12 is arranged as the outermost layer in the lamination direction, and the upper and lower surfaces of the laminated body are covered with the cover layer 13 . The cover layer 13 is mainly composed of a ceramic material. For example, the material of the cover layer 13 is the same as the main component of the dielectric layer 11 and the ceramic material.

The size of the multilayer ceramic capacitor 100 is, for example, length 0.2 mm, width 0.125 mm, and height 0.125 mm, or length 0.4 mm, width 0.2 mm, height 0.2 mm, or length 0.6 mm, 0.3 mm wide and 0.3 mm high; or 1.0 mm long, 0.5 mm wide and 0.5 mm high; or 3.2 mm long, 1.6 mm wide and 0.5 mm high. 1.6 mm in height, or 4.5 mm in length, 3.2 mm in width and 2.5 mm in height, but are not limited to these sizes.

The internal electrode layers 12 are mainly composed of base metals such as Ni (nickel), Cu (copper), and Sn (tin). As the internal electrode layers 12, noble metals such as Pt (platinum), Pd (palladium), Ag (silver), Au (gold), and alloys containing these may be used.

The dielectric layer 11 is mainly composed of, for example, a ceramic material whose main phase is a perovskite structure represented by the general formula _ABO3 . Note that the perovskite structure contains ABO _3-α deviating from the stoichiometric composition. For example, the ceramic materials include BaTiO ₃ (barium titanate), CaZrO ₃ (calcium zirconate), CaTiO ₃ (calcium titanate), SrTiO ₃ (strontium titanate), and Ba _1-xy forming a perovskite structure. Ca _x Sr _y Ti _1-z Zr _z O ₃ (0≦x≦1, 0≦y≦1, 0≦z≦1) and the like can be used.

In order to reduce the size and increase the capacity of the multilayer ceramic capacitor 100, it is desired to reduce the thickness of the dielectric layer 11. FIG. However, if the thickness of the dielectric layer 11 is reduced, the life characteristics may deteriorate due to dielectric breakdown or the like, and the reliability may decrease.

Here, the decrease in reliability will be explained. The dielectric layer 11 is mainly composed of a ceramic material using a ceramic raw material powder having a perovskite structure represented by the general formula ABO ₃ as a main phase. Oxygen vacancies occur in _ABO3 . Voltage is repeatedly applied to the dielectric layer 11 when the multilayer ceramic capacitor 100 is used. At this time, the barrier is destroyed by migration of oxygen vacancies. In other words, oxygen defects in the perovskite structure are a factor in reducing the reliability of the dielectric layer 11 .

Therefore, in the present embodiment, an element functioning as a donor is contained in the B site of the perovskite structure (substitution solid solution). Examples of elements that function as donors include Mo (molybdenum), Nb (niobium), Ta (tantalum), and W (tungsten). Oxygen vacancies in the perovskite structure are suppressed by substitution solid solution of the element functioning as a donor at the B site. Thereby, the life of the dielectric layer 11 can be extended and the reliability can be improved.

If there are too few elements that function as donors at the B site, oxygen defects may not be sufficiently suppressed. Therefore, at the B site, it is preferable to set a lower limit for the substitution solid-solution amount of the element that functions as a donor. For example, in the B site, when the main component element of the B site is 100 atm %, the element that functions as a donor preferably has a substitution solid solution of 0.05 atm % or more, and a substitution solid solution of 0.1 atm % or more. It is more preferable to have

On the other hand, if there are too many elements that function as donors at the B site, there is a possibility that a problem such as a decrease in insulating properties may occur. Therefore, at the B site, it is preferable to set an upper limit for the substitution solid-solution amount of the element that functions as a donor. For example, at the B site, the substitution solid solution of 0.3 atm % or less of the element functioning as a donor is more preferable, and the substitution solid solution of 0.25 atm % or less is more preferable.

Next, the dielectric layer 11 whose main component is a ceramic material using a ceramic raw material powder whose main phase is a perovskite structure is fired in a reducing atmosphere, and then re-oxidized to further suppress oxygen defects. . If the rare earth element is contained in both the A site and the B site during reoxidation (if the rare earth element is solid-dissolved by substitution), the amount of oxygen defects after firing is suppressed. As a result, long life characteristics can be realized while maintaining insulation (IR: Insulation Resistance) characteristics. As a result, high reliability can be achieved. Therefore, in this embodiment, both the A site and the B site have a substitution solid solution of the rare earth element.

If the amount of rare earth element substituted solid solution to the A site (A site solid solution amount) is too large relative to the substitution solid solution amount of the rare earth element to the B site (B site solid solution amount), donor addition to perovskite will occur. There is a risk of being overdone. In this case, the insulation characteristics may deteriorate. On the other hand, if the B-site solid-solution amount is too large with respect to the A-site solid-solution amount, there is a possibility that the acceptor is excessively added to the perovskite. In this case, the amount of oxygen defects may increase and the life characteristics may deteriorate. Therefore, by setting the ratio of the A-site solid-solution amount to the B-site solid-solution amount to around 1, the amount of oxygen defects after firing is suppressed, and high reliability with an excellent balance between insulation characteristics and life characteristics is achieved. will be obtained. Specifically, 0.75≦(A-site solid-solution amount/B-site solid-solution amount)≦1.25. From the viewpoint of further suppressing the state of excessive donor addition, it is preferable that (A-site solid-solution amount/B-site solid-solution amount)≦1.20, (A-site solid-solution amount/B-site solid-solution amount) It is more preferably ≦1.10, and further preferably (A-site solid-solution amount/B-site solid-solution amount)≦1.05. From the viewpoint of further suppressing the state of excessive addition of acceptors, it is preferable that 0.90 ≤ (A site solid solution amount/B site solid solution amount), and 0.95 ≤ (A site solid solution amount/B site solid solution amount).

If the amount of rare earth elements in the A site and B site is too low, the amount of oxygen defects after firing may not be sufficiently suppressed. Therefore, in the A site and the B site, it is preferable to set a lower limit for the total amount of the rare earth element substituted and solid-solved. For example, in the A site and the B site, the total amount of solid-solution by substitution of rare earth elements is preferably 0.2 atm % or more, more preferably 0.3 atm % or more. Atm % here means the concentration when the B site element of ABO ₃ in the ceramic raw material powder is 100 atm %.

On the other hand, if the amount of the rare earth element in the A site and the B site is too large, the tetragonality of the crystal grains may deteriorate, and the dielectric constant may decrease. Therefore, in the A site and the B site, it is preferable to set an upper limit on the total amount of the substitution solid solution of the rare earth elements. For example, in the A site and the B site, the total amount of the substituted solid solution of rare earth elements is preferably 1.0 atm% or less, more preferably 0.9 atm% or less.

As rare earth elements, Y (yttrium), La (lanthanum), Ce (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium) and the like can be used. Note that the ionic radius of the A site and the ionic radius of the B site are different. In order to make a substitution solid solution of the rare earth element in the A site and the B site with good balance, the ionic radius of the rare earth element is preferably between the ionic radius of the A site and the ionic radius of the B site. For example, according to Table 1, when _BaTiO3 is used as perovskite, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Tm, Yb, etc. are substituted. A solid solution is preferred. The source of Table 1 is "RD Shannon, Acta Crystallogr., A32, 751 (1976)".

Note that La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, etc., which have relatively large ionic radii, tend to form a substitution solid solution at the A site. On the other hand, Er, Tm, Yb, etc., which have relatively small ionic radii, tend to form a substitution solid solution at the B site. Therefore, when La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, etc. are dissolved by substitution, it is preferable that Er, Tm, Yb, etc. are also dissolved by substitution.

In addition, the value of "m" is too small in perovskite (A _m BO ₃ ) in which an element functioning as a donor is in a substitution solid solution at the B site and a rare earth element is in a substitution solid solution at both the A site and the B site. As a result, there arises a problem that insulation deteriorates. Therefore, it is preferable to set a lower limit on the value of "m". Specifically, it is preferable that m≧1.002. On the other hand, if the value of "m" is too large, problems such as deterioration of sinterability will occur. Therefore, it is preferable to set an upper limit for the value of "m". Specifically, it is preferable that m≦1.010.

The average crystal grain size of the main component ceramic in the dielectric layer 11 is preferably 80 nm to 300 nm, more preferably 80 nm to 200 nm. If the average crystal grain size of the main component ceramic is small, the dielectric constant will be low, and the desired capacitance may not be obtained. This is because, in the case of a thickness of , the grain boundary area that acts as a migration barrier for oxygen defects is reduced, which may deteriorate the life characteristics.

High reliability can also be obtained by thickening the dielectric layer 11 . However, in this case, the size of the multilayer ceramic capacitor 100 is increased. Therefore, the present embodiment is particularly effective for the small-sized multilayer ceramic capacitor 100. FIG. For example, the present embodiment is particularly effective in a thin laminated ceramic capacitor in which the dielectric layer 11 has a thickness of 1.0 μm or less. Furthermore, if the thickness of the dielectric layer 11 is set to 0.4 μm or less, a more compact and highly reliable laminated ceramic capacitor can be obtained. Moreover, the thickness of the dielectric layer 11 is more preferably 0.2 μm or more so as not to lower the insulation resistance value.

Next, a method for manufacturing the laminated ceramic capacitor 100 will be described. FIG. 2 is a diagram illustrating the flow of the manufacturing method of the multilayer ceramic capacitor 100. As shown in FIG.

(Raw material powder preparation process)
First, a ceramic raw material powder having a perovskite structure represented by the general formula _ABO3 as a main phase, an element functioning as a donor at the B site and a rare earth element at both the A site and the B site. prepare. A ceramic material using the ceramic raw material powder is the main component of the dielectric layer 11 . Various methods are conventionally known as methods for synthesizing the ceramic raw material powder, such as a solid phase synthesis method, a sol-gel synthesis method, a hydrothermal synthesis method, and the like. In addition, when the substitution solid-solution amount of the rare earth element to the A site is the A-site solid-solution amount, and the substitution solid-solution amount of the rare earth element to the B-site is the B-site solid-solution amount, 0.75 ≤ (A-site Solid solution amount/B site solid solution amount)≦1.25. As an example, a solid-phase synthesis method will be described. First, TiO ₂ powder and BaCO ₃ powder are mixed with a solvent such as pure water and a dispersant to prepare a slurry. Next, a neutralized solution of a rare earth element dissolved in acetic acid is added to the slurry, and kneaded and dispersed. It is also possible to add powder of a molybdenum compound to the slurry and perform the kneading/dispersion treatment in a state in which the molybdenum is ionized or complexed. Kneading/dispersion is carried out using a bead mill or the like for 20 to 30 hours. The slurry is then dried to obtain green wood. This raw material is calcined at 800° C. to 1150° C. for the first time to obtain a ceramic raw material powder.

A predetermined additive compound is added to the obtained ceramic raw material powder according to the purpose. Additive compounds include oxides of Mg (magnesium), Mn (manganese), V (vanadium), and Cr (chromium), as well as Co (cobalt), Ni, Li (lithium), B (boron), Na (sodium ), K (potassium) and Si (silicon) oxides or glasses.

For example, the ceramic raw material powder is mixed with a compound containing an additive compound, and the mixture is calcined at 820 to 1150° C. for the second time. Subsequent wet mixing, drying and grinding to prepare the ceramic material. For example, the average particle size of the ceramic material is preferably 50 to 150 nm from the viewpoint of thinning the dielectric layer 11 . For example, the ceramic material obtained as described above may be pulverized to adjust the particle size, or combined with a classification process to adjust the particle size. Through the above steps, a ceramic material that is the main component of the dielectric layer is obtained.

(Lamination process)
Next, a binder such as polyvinyl butyral (PVB) resin, an organic solvent such as ethanol or toluene, and a plasticizer are added to the resulting ceramic material and wet-mixed. Using the obtained slurry, a belt-shaped dielectric green sheet having a thickness of, for example, 3 μm to 10 μm is coated on the substrate by, for example, a die coater method or a doctor blade method, and dried.

Next, by printing a metal conductive paste for forming internal electrodes containing an organic binder on the surface of the dielectric green sheet by screen printing, gravure printing, etc., the internal electrodes are alternately led out to a pair of external electrodes having different polarities. Lay out the layer pattern. Ceramic particles are added to the metal conductive paste as a common material. Although the main component of the ceramic particles is not particularly limited, it is preferably the same as the main component ceramic of the dielectric layer 11 . For example, BaTiO ₃ having an average particle size of 50 nm or less may be uniformly dispersed.

After that, the dielectric green sheet on which the internal electrode layer pattern is printed is punched into a predetermined size, and the punched dielectric green sheet is separated into the internal electrode layer 12 and the dielectric layer 11 in a state where the base material is peeled off. are alternately arranged, and the edges of the internal electrode layers 12 are alternately exposed on both end surfaces in the length direction of the dielectric layer 11, and are alternately led out to a pair of external electrodes 20a and 20b having different polarities. A predetermined number of layers (for example, 100 to 500 layers) are laminated. Cover sheets for forming the cover layer 13 are pressure-bonded to the top and bottom of the laminated dielectric green sheets, and cut into a predetermined chip size (for example, 1.0 mm×0.5 mm).

After removing the binder from the obtained ceramic laminate in an _N2 atmosphere, a metal filler containing the main component metal of the external electrodes 20a and 20b, a common material, a binder, a solvent, etc. are applied from both end surfaces to each side surface of the ceramic laminate. A metal paste is applied as a base layer for the external electrodes 20a and 20b, and dried.

(Baking process)
The molded body thus obtained is subjected to binder removal treatment in an N ₂ atmosphere at 250 to 500° C., and then in a reducing atmosphere with an oxygen partial pressure of 10 ⁻⁵ to 10 ⁻⁸ atm at 1100 to 1300° C. for 10 minutes. By firing for up to 2 hours, the particles in the compact are sintered and grain growth occurs. Thus, a sintered body is obtained.

(Reoxidation treatment step)
Thereafter, re-oxidation treatment is performed at 600° C. to 1000° C. in an N ₂ gas atmosphere. Oxygen defects are suppressed by this step.

(External electrode forming step)
After that, metal coating such as Cu, Ni, and Sn is applied to the underlying layers of the external electrodes 20a and 20b by plating.

According to the manufacturing method according to the present embodiment, in the ceramic raw material powder used in the raw material powder preparation step, the element that functions as a donor is substituted and solid-solved in the B site of the perovskite structure. Oxygen defects are suppressed. Thereby, the life of the dielectric layer 11 can be extended and the reliability can be improved. In addition, since the rare earth element is substituted and solid-solved in the A site and the B site, the amount of oxygen defects after firing is suppressed. As a result, long life characteristics can be achieved while maintaining insulation characteristics. As a result, high reliability can be achieved. In addition, by setting 0.75≦(A-site solid-solution amount/B-site solid-solution amount)≦1.25, the amount of oxygen defects after firing is suppressed, and a high-quality steel with excellent balance between insulation properties and life properties is obtained. gains credibility.

From the viewpoint of further suppressing the state of excessive donor addition, it is preferable that (A-site solid-solution amount/B-site solid-solution amount)≦1.20, (A-site solid-solution amount/B-site solid-solution amount) It is more preferably ≦1.10, and further preferably (A-site solid-solution amount/B-site solid-solution amount)≦1.05. From the viewpoint of further suppressing the state of excessive addition of acceptors, it is preferable that 0.90 ≤ (A site solid solution amount/B site solid solution amount), and 0.95 ≤ (A site solid solution amount/B site solid solution amount).

If there are too few elements that function as donors at the B site, oxygen defects may not be sufficiently suppressed. Therefore, at the B site, it is preferable to set a lower limit for the substitution solid-solution amount of the element that functions as a donor. For example, in the B site, when the main component element of the B site is 100 atm %, the element that functions as a donor preferably has a substitution solid solution of 0.05 atm % or more, and a substitution solid solution of 0.1 atm % or more. It is more preferable to have

On the other hand, if there are too many elements that function as donors at the B site, there is a possibility that problems such as a decrease in insulating properties may occur. Therefore, at the B site, it is preferable to set an upper limit for the substitution solid-solution amount of the element that functions as a donor. For example, at the B site, the substitution solid solution of 0.3 atm % or less of the element functioning as a donor is more preferable, and the substitution solid solution of 0.25 atm % or less is more preferable.

If the amount of rare earth elements in the A site and B site is too low, the amount of oxygen defects after firing may not be sufficiently suppressed. Therefore, in the A site and the B site, it is preferable to set a lower limit for the total amount of the rare earth element substituted and solid-solved. For example, in the A site and the B site, the total amount of solid-solution by substitution of rare earth elements is preferably 0.2 atm % or more, more preferably 0.3 atm % or more. Atm % here means the concentration when the B site element of ABO ₃ in the ceramic raw material powder is 100 atm %.

On the other hand, if the amount of the rare earth element in the A site and the B site is too large, the tetragonality of the crystal grains may deteriorate, which may cause a problem such as a decrease in the dielectric constant. Therefore, in the A site and the B site, it is preferable to set an upper limit on the total amount of the substitution solid solution of the rare earth elements. For example, in the A site and the B site, the total amount of the substituted solid solution of rare earth elements is preferably 1.0 atm% or less, more preferably 0.9 atm% or less.

Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, etc. can be used as rare earth elements. Note that the ionic radius of the A site and the ionic radius of the B site are different. In order to make a substitution solid solution of the rare earth element in the A site and the B site with good balance, the ionic radius of the rare earth element is preferably between the ionic radius of the A site and the ionic radius of the B site. For example, according to Table 1, when _BaTiO3 is used as perovskite, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Tm, Yb, etc. are substituted. A solid solution is preferred.

Note that La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, etc., which have relatively large ionic radii, tend to form a substitution solid solution at the A site. On the other hand, Er, Tm, Yb, etc., which have relatively small ionic radii, tend to form a substitution solid solution at the B site. Therefore, when La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, etc. are dissolved by substitution, it is preferable that Er, Tm, Yb, etc. are also dissolved by substitution.

In addition, the value of "m" is too small in perovskite (A _m BO ₃ ) in which an element functioning as a donor is in a substitution solid solution at the B site and a rare earth element is in a substitution solid solution at both the A site and the B site. As a result, there arises a problem that insulation deteriorates. Therefore, it is preferable to set a lower limit on the value of "m". Specifically, it is preferable that m≧1.002. On the other hand, if the value of "m" is too large, problems such as deterioration of sinterability will occur. Therefore, it is preferable to set an upper limit for the value of "m". Specifically, it is preferable that m≦1.010.

Hereinafter, multilayer ceramic capacitors according to the embodiments were produced and their characteristics were examined.

First, a ceramic raw material powder of BaTiO ₃ was prepared in which an element functioning as a donor was solid-dissolved by substitution at the B site and a rare earth element was solid-dissolved by substitution at both the A site and the B site. The average particle size is 150 nm. In all of Examples 1 to 11 and Comparative Examples 1 to 9, 0.2 atm % of Mo was substituted and dissolved in the B site when Ti was 100 atm %.

In Examples 1 and 2, a ceramic raw material powder in which 0.2 atm % of Ho was substituted and solid-dissolved as a rare earth element was used, and then 0.8 atm % of Ho was added as Ho ₂ O ₃ . In Examples 3 to 7, ceramic raw material powder in which 0.5 atm % of Ho was substituted and solid-dissolved as a rare earth element was used, and then 0.5 atm % of Ho was added as Ho ₂ O ₃ . In Example 8, a ceramic raw material powder in which 0.25 atm % of Gd and _Yb were substituted and _solid -dissolved as rare earth elements was used. % equivalent Yb was added as Yb ₂ O ₃ . In Examples 9 to 11, a ceramic raw material powder in which 1.0 atm % of Ho was substituted and solid-dissolved as a rare earth element was used. In Comparative Example 1, Ho was added as Ho ₂ O ₃ in an amount equivalent to 1.0 atm % without causing a substitution solid solution of the rare earth element in the ceramic raw material powder. In Comparative Example 2, a ceramic raw material powder in which 0.2 atm % of Ho was dissolved by substitution was used, and then 0.8 atm % of Ho was added as Ho ₂ O ₃ . In Comparative Examples 3 to 5, a ceramic raw material powder in which 0.5 atm % of Ho was dissolved by substitution was used, and then 0.5 atm % of Ho was added as Ho ₂ O ₃ . In Comparative Example 6, a ceramic raw material powder in which 0.2 atm% and 0.3 atm% of Gd and Yb, respectively, were substituted and solid-dissolved as rare earth elements was _used , and then 0.2 atm% of Gd was added as _Gd2O3 . Then, Yb corresponding to 0.3 atm % was added as Yb ₂ O ₃ . In Comparative Example 7, a ceramic raw material powder in which 0.3 atm% and 0.2 atm% of Gd and Yb, respectively, were substituted and solid-dissolved as rare earth elements was used _, and then Gd equivalent to 0.3 atm% was added as _Gd2O3 . Yb corresponding to 0.2 atm % was added as Yb ₂ O ₃ . In Comparative Examples 8 and 9, ceramic raw material powders in which 1.0 atm % of Ho was substituted and dissolved as a rare earth element were used. Atm % in this paragraph means the concentration when the B site of ABO ₃ in the ceramic raw material powder is 100 atm %.

In Example 1, (A-site solid-solution amount/B-site solid-solution amount) was 0.95. In Example 2, (A-site solid-solution amount/B-site solid-solution amount) was 1.10. In Example 3, (A-site solid-solution amount/B-site solid-solution amount) was 0.75. In Example 4, (A-site solid-solution amount/B-site solid-solution amount) was 0.95. In Example 5, (A-site solid-solution amount/B-site solid-solution amount) was 1.00. In Example 6, (A-site solid-solution amount/B-site solid-solution amount) was 1.05. In Example 7, (A-site solid-solution amount/B-site solid-solution amount) was 1.25. In Example 8, (A-site solid-solution amount/B-site solid-solution amount) was 1.10. In Example 9, (A-site solid-solution amount/B-site solid-solution amount) was 0.75. In Example 10, (A-site solid-solution amount/B-site solid-solution amount) was 1.03. In Example 11, (A-site solid-solution amount/B-site solid-solution amount) was 1.20. In Comparative Example 2, (A-site solid-solution amount/B-site solid-solution amount) was 1.32. In Comparative Example 3, (A-site solid-solution amount/B-site solid-solution amount) was 0.50. In Comparative Example 4, (A-site solid-solution amount/B-site solid-solution amount) was 1.35. In Comparative Example 5, (A-site solid-solution amount/B-site solid-solution amount) was 1.50. In Comparative Example 6, (A-site solid-solution amount/B-site solid-solution amount) was 0.70. In Comparative Example 7, (A-site solid-solution amount/B-site solid-solution amount) was 1.50. In Comparative Example 8, (A-site solid-solution amount/B-site solid-solution amount) was 0.66. In Example 9, (A-site solid-solution amount/B-site solid-solution amount) was 1.30.

The substitution solid solution amount was measured by energy dispersive X-ray fluorescence spectroscopy (EDS) using a transmission electron microscope (TEM) on a sample obtained by etching the ceramic raw material powder into a hemispherical shape with Ar ions. did. (A-site solid-solution amount/B-site solid-solution amount) was measured by high-angle scattering annular dark-field scanning transmission microscopy (HADDF-STEM) for the same processed sample.

In all of Examples 1 to 11 and Comparative Examples 1 to 9, in A _m BO ₃ in a state in which Mo is substituted in solid solution at the B site and rare earth elements are substituted in both the A site and the B site. , and the value of “m” was set to 1.002.

Add 1.0 _mol % of MgO as an additive to the ceramic raw powder, add 0.05 mol% each of MnO and _V2O5 as additives, and add 1.0 mol each of _SiO2 and _BaCO3 as sintering aids. % was added. In this case, "mol %" is a numerical value when ABO ₃ in the ceramic raw material powder is 100 mol %.

Ceramic raw material powders to which additives and sintering aids were added were sufficiently wet-mixed and pulverized in a ball mill to obtain a ceramic material. A dielectric green sheet was prepared by adding an organic binder and a solvent to a ceramic material by the doctor blade method. The coating thickness of the dielectric green sheet was 0.8 μm, polyvinyl butyral (PVB) or the like was used as an organic binder, and ethanol, toluic acid, or the like was added as a solvent. In addition, a plasticizer and the like were added. Next, an internal electrode containing a powder of the main component metal (Ni) of the internal electrode layer 12, a common material (barium titanate), a binder (ethyl cellulose), a solvent, and other auxiliary agents as needed A forming conductive paste was prepared with a planetary ball mill.

A conductive paste for forming internal electrodes was screen-printed on the dielectric sheet. 250 sheets on which the conductive paste for forming internal electrodes was printed were stacked, and cover sheets were laminated on the upper and lower sides thereof. After that, a ceramic laminate was obtained by thermocompression bonding and cut into a predetermined shape. After the obtained ceramic laminate was debindered in an _N2 atmosphere, the external electrode 20a containing a metal filler containing Ni as a main component, a common material, a binder, a solvent, etc. , 20b was applied and dried. After that, the metal paste was sintered simultaneously with the ceramic laminate at 1100° C. to 1300° C. for 10 minutes to 2 hours in a reducing atmosphere to obtain a sintered body.

The shape and dimensions of the obtained sintered body were 0.6 mm long, 0.3 mm wide and 0.3 mm high. After the sintered body is re-oxidized under _N2 atmosphere at 800° C., it is plated to form a Cu-plated layer, a Ni-plated layer and an Sn-plated layer on the surfaces of the underlying layers of the external electrodes 20a and 20b. Thus, the external electrodes 20a and 20b were formed, and the multilayer ceramic capacitor 100 was obtained.

(analysis)
Twenty samples were prepared for each of Examples 1-11 and Comparative Examples 1-9. A life characteristic test was performed on each sample to measure the average life. Note that the life characteristic test was performed at 125° C. with a DC voltage of 10 V applied, the leakage current value was measured with an ammeter, and the time until dielectric breakdown was taken as the life value. An insulation resistance test was conducted on each sample to measure the average insulation resistance. The insulation resistance test was performed at room temperature by applying a DC voltage of 10 V, and the resistance was measured from the current value after 60 seconds.

When the average life span was 100 minutes or less, the life characteristic was judged as failing "x". When the insulation resistance was 10 MΩ or less, the insulation characteristics were judged as failing "x". When either one of the life characteristics and the insulation characteristics was judged to be unsatisfactory, the reliability was judged to be "failed". The results are shown in FIG.

In Comparative Example 1, both the life property and the insulation property were determined to be unacceptable. It is considered that this is because the ceramic raw material powder in which the rare earth element was not dissolved by substitution was used, and thus the rare earth element could not be sufficiently dissolved by substitution. In Comparative Examples 2, 4, 5, 7 and 9, the life characteristics were judged to be acceptable, while the insulation characteristics were judged to be unacceptable. It is considered that this is because (A site solid solution amount/B site solid solution amount) exceeded 1.25. In Comparative Examples 3, 6, and 8, the insulation properties were judged to be acceptable, while the life properties were judged to be unsatisfactory. It is considered that this is because (A-site solid-solution amount/B-site solid-solution amount) was less than 0.75.

On the other hand, in all of Examples 1 to 11, both life characteristics and insulation characteristics were determined to be acceptable. In this method, an element that functions as a donor is dissolved in the B site by substitution, and a rare earth element is dissolved in both the A site and the B site. It is considered that this is because the value falls within the range of 1.25 or less.

In Examples 4 and 5, compared with Example 3, the insulation resistance and life characteristics are even better. It is considered that this is because (A site solid solution amount/B site solid solution amount) became 0.95 or more. In Example 2, compared with Example 7, the insulation resistance and life characteristics are better. It is considered that this is because the ratio (A-site solid-solution amount/B-site solid-solution amount) was 1.10 or less. In Examples 5 and 6, compared with Example 2, the insulation resistance and life characteristics are even better. It is considered that this is because the (A-site solid-solution amount/B-site solid-solution amount) became 1.05 or less. In Example 10, compared with Example 9, the life characteristics are even better. It is considered that this is because (A site solid solution amount/B site solid solution amount) became 0.95 or more. Further, in Example 10, compared with Example 11, the life characteristics are even better. It is considered that this is because the (A-site solid-solution amount/B-site solid-solution amount) became 1.05 or less.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations can be made within the scope of the gist of the present invention described in the scope of claims. Change is possible.

REFERENCE SIGNS LIST 10 laminated chip 11 dielectric layer 12 internal electrode layer 13 cover layer 20a, 20b external electrode 100 laminated ceramic capacitor

Claims (11)

A laminated body in which dielectric layers and internal electrode layers are alternately laminated,
The main component of the dielectric layer is a ceramic material that has a perovskite structure represented by the general formula _ABO3 as a main phase, contains an element that functions as a donor at the B site, and contains a rare earth element at both the A site and the B site. can be,
the ceramic material contains Ba and Ti;
The same kind of rare earth element is dissolved in the A site and the B site,
The rare earth element contained in the A site includes at least one of La, Ce, Pr, Nd, Pm, Sm, Eu and Gd,
The rare earth element contained in the B site includes at least one of Er, Tm and Yb,
The ratio of the solid-solution amount of the rare earth element dissolved in the A site (A-site solid-solution amount) to the solid-solution amount of the rare-earth element solid-solution in the B site (B-site solid solution amount) is 0.5. A multilayer ceramic capacitor that satisfies 75≦(A-site solid-solution amount/B-site solid-solution amount)≦1.25. 2. The multilayer ceramic capacitor according to claim 1 , wherein said element functioning as a donor includes Mo. 3. The multilayer ceramic capacitor according to claim 1 , wherein said rare earth element contains at least one of Tb, Dy, Ho and Y. 4. The multilayer ceramic capacitor according to claim 1, wherein the dielectric layers have a thickness of 0.4 μm or less in the lamination direction. The ratio of the solid solution amount of the rare earth element dissolved in the A site (A site solid solution amount) to the solid solution amount of the rare earth element solid dissolved in the B site (B site solid solution amount) is 0.5. 5. The multilayer ceramic capacitor according to claim 1 , wherein 95≦(A-site solid-solution amount/B-site solid-solution amount)≦1.05 is satisfied. A ceramic raw material powder containing Ba and Ti,
The main phase is a perovskite structure represented by the general formula _ABO3 , the B site contains an element that functions as a donor, both the A site and the B site contain a rare earth element,
The same kind of rare earth element is dissolved in the A site and the B site,
The rare earth element contained in the A site includes at least one of La, Ce, Pr, Nd, Pm, Sm, Eu and Gd,
The rare earth element contained in the B site includes at least one of Er, Tm and Yb,
The ratio of the solid solution amount of the rare earth element dissolved in the A site (A site solid solution amount) to the solid solution amount of the rare earth element solid dissolved in the B site (B site solid solution amount) is 0.5. A ceramic raw material powder that satisfies 75≦(A-site solid-solution amount/B-site solid-solution amount)≦1.25. 7. The ceramic raw material powder according to claim 6 , wherein the element functioning as a donor contains Mo. 8. The ceramic raw material powder according to claim 6 , wherein the rare earth element contains at least one of Tb, Dy, Ho and Y. The ratio of the solid solution amount of the rare earth element dissolved in the A site (A site solid solution amount) to the solid solution amount of the rare earth element solid dissolved in the B site (B site solid solution amount) is 0.5. 9. The ceramic raw material powder according to any one of claims 6 to 8 , wherein 95≤(A-site solid-solution amount/B-site solid-solution amount)≤1.05. 6. The multilayer ceramic capacitor according to claim 1 , wherein Ho is dissolved in said A site and said B site. 10. The ceramic raw material powder according to any one of claims 6 to 9 , wherein Ho is dissolved in the A site and the B site.

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