JPS6117322B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a dielectric ceramic composition having extremely fine grain size and long life. Conventionally, high dielectric constant dielectric ceramic compositions have been used by adding strontium titanate, barium stannate, calcium stannate, barium zirconate, etc. as shifters to barium titanate to shift its Curie point to around room temperature. However, its crystal grain size is large at 5 μm or more, making it unsuitable for products with large electric field strengths such as multilayer capacitors. In other words, when the crystal grain size is large, the electric field strength applied to each crystal grain becomes large,
As a result, the breakdown voltage is low, the number of void defects that gather at grain boundaries is increased, the life is shortened, and the reliability is lowered. The present inventors have studied to solve the drawbacks of the conventional compositions described above and provide a dielectric ceramic composition that is extremely fine with a crystal grain size of less than 5 μm and has a long lifespan. The inventors have discovered that when samarium oxide is added to barium, the crystal grains of the resulting dielectric ceramic composition become finer, and the present invention has been achieved. That is, the basic gist of the present invention is that BaO39.0-53.3mol%
A dielectric ceramic composition comprising 1.0 to 1.7 mol% of Sm ₂ O ₃ and 45.0 to 60.0 mol% of TiO ₂ . The present invention further provides the above BaO39.0 to 53.3 mol%,
It can be configured by adding 1.0 to 10.0 mol% of CaO to the basic composition of 1.0 to 1.7 mol% of Sm ₂ O ₃ and 45.0 to 60.0 mol% of TiO ₂ . Due to the above-mentioned structure, the composition of the present invention has an extremely fine crystal grain size, as shown in the examples, and is therefore optimal for products with large electric field strengths such as multilayer capacitors. That is, since the crystal grain size is fine, the electric field strength applied to each crystal grain is reduced, thereby increasing the breakdown voltage, extending the life, and improving reliability. Further, the composition of the present invention has a high dielectric constant and a low dielectric loss tangent,
As the examples show, it is sufficiently practical. As described above, the reason why the crystal grain size of the composition of the present invention is fine is that a liquid phase is generated when the raw material mixture blended to have the above composition is fired, thereby lowering the sintering temperature. This is to suppress excessive growth of crystals. In the composition of the composition of the present invention, if the amount of samarium oxide is less than 1.0 mol%, the dielectric loss tangent will be high, and if it exceeds 1.7 mol%, the Curie point will shift too much, making it impractical. The amount of titanium oxide
If it is less than 45.0 mol%, sintering becomes difficult, and if it exceeds 60.0 mol%, giant crystals will occur and welding to the substrate will occur.
When the amount of barium oxide is less than 39.0 mol%, giant crystals are generated and welding to the base material occurs, and when it exceeds 53.3 mol%, sintering becomes difficult. In addition, calcium oxide promotes porcelain formation and also has the effect of a shifter. If the amount is less than 1.0 mol%, there is no effect of addition, and if it exceeds 10.0 mol%, the crystal grain size increases. The present invention further provides that the main components consisting of oxides of barium, samarium and titanium or oxides of barium, samarium, titanium and calcium are selected from among the group consisting of oxides of manganese, chromium, iron, nickel and cobalt. At least one selected from MnO ₂ , Cr ₂ O ₃ ,
0.05 of the main components in terms of FeO, NiO and CoO
It is possible to have a structure in which 0.6% by weight is added. These additives have the effect of improving the sinterability and dielectric loss tangent of porcelain, and if the amount added is less than 0.05% by weight, there is no effect, and if it exceeds 0.6% by weight, the dielectric constant decreases. The composition of the present invention can be produced by, for example, wet-mixing and pulverizing a weighed raw material mixture in a ball mill so that it has the composition of the composition of the present invention after sintering, and dehydrating and drying the resulting mixed and pulverized product. Thereafter, it can be obtained by pressure molding into a predetermined shape and firing. In this case, the barium compound used as a raw material is
BaCO ₃ , BaC ₂ O ₄ , samarium compound Sm ₂ O ₃ ,
Sm ₂ (C ₂ O ₄ ) ₃ , titanium compounds are TiO ₂ , Ti
(C ₂ O ₄ ) ₂ , calcium compounds are preferably CaCO ₃ and CaO, and raw materials for additives include MnCO ₃ ,
_MnO2 , _Cr2O3 , _CrO3 , FeO, _Fe2O3 , _{NiO ,}
NiO ₂ , CoO and Co ₂ O ₃ are preferred. Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. Example 1 BaCO ₃ and Sm ₂ O ₃ , each of grade 1 reagent, were used as raw materials.
After firing, the TiO ₂ and TiO 2 were weighed so that the main component composition ratio shown in Table 1 was obtained, wet mixed and crushed in a ball mill for 20 hours, dehydrated and dried, and the molding pressure
Pressure molded at 3 ton/cm ² into a disc with a diameter of 16 mm and a thickness of 0.6 mm, and the molded product was fired at a temperature of 1320 to 1320 as shown in Table 1.
After baking at 1390°C for 1 hour, samples Nos. 1 to 5 were obtained. The grain size of these samples was determined using an optical microscope.
400, and the dielectric constant and dielectric loss tangent were determined by baking silver electrodes on both sides of the sample and using YHP digital XCR meter model 4274A at a measurement temperature of 25°C, a measurement voltage of 1.0Vrms, and a measurement frequency of 1.0KHz. The measurement results of these physical properties are shown in Table 1.

[Table] As shown in Table 1, all the samples obtained were as follows:
A dielectric ceramic composition having a crystal grain size of 3.0 μm or less and a practical dielectric constant and dielectric loss tangent,
It is ideal for products with large electric field strengths such as multilayer capacitors. Example 2 First grade reagent BaC ₂ O ₄ and Sm ₂ as raw materials
(C ₂ O ₄ ) ₃ , Ti(C ₂ O ₄ ) ₂ and CaCO ₃ were weighed out so as to have the main component composition ratio shown in Table 2 after firing,
Sample numbers 6 to 8 were obtained by processing in the same manner as in Example 1. The methods for measuring the crystal grain size, dielectric constant, and dielectric loss tangent of these samples were the same as in Example 1, and the measurement results are shown in Table 2.

[Table] As shown in Table 2, the addition of calcium oxide made it possible to lower the firing temperature. Example 3 Reagent grade 1 BaCO ₃ as raw materials,
Sm ₂ O ₃ and TiO ₂ are used, and MnCO ₃ , which is a first-class reagent, is used as a raw material for the additives manganese, chromium, iron, nickel, and cobalt, respectively.
Samples Nos. 9 to 15 were prepared in the same manner as in Example 1 except that Cr ₂ O ₃ , FeO, NiO, and CoO were added.
I got it. The methods for measuring the crystal grain size, dielectric constant, and dielectric loss tangent of these samples were the same as in Example 1, and the measurement results are shown in Table 3.

【table】

[Table] As shown in Table 3, manganese, chromium, iron,
With the addition of nickel and cobalt oxides,
It was possible to lower the firing temperature and dielectric loss tangent. Example 4 Substituting CaCO ₃ as raw material for calcium oxide
Using CaO, the additives manganese, chromium,
As raw materials for iron, nickel, and cobalt oxides, primary reagents MnO ₂ , CrO ₃ , Fe ₂ O ₃ ,
Samples Nos. 16 to 22 were obtained in the same manner as in Example 2 except that NiO ₂ and Co ₂ O ₃ were added. The methods for measuring the crystal grain size, dielectric constant, and dielectric loss tangent of these samples were the same as in Example 1, and the measurement results are shown in Table 4. As Table 4 shows, manganese, chromium, iron,
By adding nickel and cobalt oxides, the firing temperature and dielectric loss tangent can be lowered.

【table】

Claims (1)

[Claims] 1. Barium, samarium, and titanium oxides are converted into BaO, Sm ₂ O ₃ and TiO _2, respectively, and BaO39.0 to 53.3 mol% and Sm ₂ O ₃ 1.0 to 53.3 mol%.
A dielectric ceramic composition comprising 1.7 mol% of TiO ₂ and 45.0 to 60.0 mol% of TiO 2 . 2 The oxides of barium, samarium, titanium and calcium are converted into BaO, Sm ₂ O ₃ , TiO ₂ and CaO, respectively, and are calculated as BaO39.0 to 53.3 mol%.
Sm ₂ O ₃ 1.0 to 1.7 mol% and TiO ₂ 45.0 to 60.0 mol%
and 1.0 to 10.0 mol% of CaO. 3 Barium, samarium, and titanium oxides are converted into BaO, Sm ₂ O ₃ and TiO ₂ respectively, and BaO is 39.0 to 53.3 mol% and Sm ₂ O ₃ is 1.0 to 53.3 mol%.
The main components are 1.7 mol% of TiO 2 and 45.0 to 60.0 mol% of TiO ₂ , and _at least one selected from the group consisting of oxides of manganese, chromium, iron, nickel and cobalt, respectively. _{2O3 ,} FeO,
0.05 to 0.05 of the main component in terms of NiO and CoO
A dielectric ceramic composition characterized by adding 0.6% by weight. 4 Barium, samarium, titanium, and calcium oxides are converted into BaO, Sm ₂ O ₃ , TiO ₂ and CaO, respectively, and are calculated as BaO39.0 to 53.3 mol%.
Sm ₂ O ₃ 1.0 to 1.7 mol% and TiO ₂ 45.0 to 60.0 mol%
and 1.0 to 10.0 mol% of CaO, and at least one selected from the group consisting of oxides of manganese, chromium, iron, nickel and cobalt, respectively, and MnO ₂ and Cr ₂ O _{3 .} , FeO, NiO and
0.05 to 0.6% by weight of the main component in terms of CoO
A dielectric ceramic composition characterized in that it is made by adding an additive.