KR100431404B1 - Piezoelectric ceramics composition for high power piezoelectric devices, piezoelectric transformer using the same and driving method of piezoelectric transformer - Google Patents

Abstract

The present invention relates to a piezoelectric ceramic composition for a high power piezoelectric device having a high mechanical quality factor (Q _m ), an electromechanical coupling factor (k _p ) and a piezoelectric strain constant (d ₃₃ ), a piezoelectric transformer using the same, and a driving method thereof. In more detail, the composition formula xPbZrO ₃ + yPbTiO ₃ + zPbMn _1/3 Nb _1/3 Sb _1/3 O ₃ (where 0.38 ≦ x ≦ 0.51 mol, 0.40 ≦ y ≦ 0.51 mol, 0.05 ≦ z ≦ 0.15 mol) The piezoelectric ceramic composition of the present invention comprising a compound as a main component can solve the problem of large power application due to heat generation, which is a disadvantage of the conventional piezoelectric transformer, and the improved piezoelectric transformer using the composition and its driving method are conventional It can solve the problem of high power application due to the small current of piezoelectric transformer and the problem of mechanical breakdown due to the concentration of mechanical stress at the edge part, and eliminate the polarization process in the longitudinal or radial direction. As just one of polarization process can produce a piezoelectric transformer can be achieved simplification of the manufacturing process.

Description

Piezoelectric ceramics composition for high power piezoelectric devices, piezoelectric transformer using the same and driving method of piezoelectric transformer

The present invention relates to a piezoelectric ceramic composition based on lead manganese-niobium-antimonium titanate zirconate, a piezoelectric transformer using the same, and a driving method thereof.

In the prior art, ceramics containing lead titanate or lead zirconate titanate (PZT) as the main component are known as piezoelectric ceramic materials. Piezoelectric ceramic compositions further containing a second component, optional third component, and various additives are known to exhibit improved piezoelectricity and electrical properties.

Piezoelectric ceramic compositions having sufficient piezoelectricity for use in ultrasonic motors and piezoelectric transformers are disclosed in lead zinc-niobate titanate zir as disclosed in Japanese Patent Publication No. 18400 (1979). It is obtained by adding manganese oxide and cobalt oxide to the cornate. Similar piezoelectric ceramic compositions in which lead is replaced with strontium, barium, and the like are disclosed in Japanese Patent Laid-Open No. 154682 (1987).

These compositions are presently used in a variety of applications, and especially in piezoelectric transformers that have been studied for a long time. These currently attract more attention because of the advantages of compactness (especially reduction in thickness), weight reduction, high efficiency and low noise compared to electronic transformers. Piezoelectric inverters for driving CCFLs have been commercialized, and application of fluorescent lamps has been attempted in order to save energy.

1 is a top view of a piezoelectric transformer for driving a conventional fluorescent lamp. Referring to Figure 1, a relatively thin square body made of piezoelectric material is divided into two areas (1, 2), each area is divided into a point-shaped area and a rectangular area in the center of the body, each area Is almost equal to the area of. Regions 1 and 2 are referred to as driving regions or driven regions (or power generation regions), respectively.

FIG. 2 is a bottom view of a conventional piezoelectric transformer. The whole of the piezoelectric transformer is composed of one electrode 4 and is used as a common ground for the input side and the output side when the piezoelectric transformer is driven.

3 is a front view and a driving method of a conventional piezoelectric transformer, and regions 1 and 2 of FIG. 1 are polarized in a thickness direction. Also, between the region 1 and the region 2 is polarized in the radial direction. As an example of the driving method, when the driving region is used as the region 1, the upper and lower surfaces are applied to the input terminals 11a and 11b, which are a pair of electrodes. On the other hand, in the driven region 2, the input terminal 11b, which is a connection line of the driving region, the output terminal 12b, which is a common grounded connection, and the output terminal 12a, which is a connection line, form a pair of electrodes to generate an AC voltage. Zone 1 and zone 2 are polarized in the thickness direction of the body, as indicated by arrows 32 and 33, and between zone 1 and zone 2, polarized in the radial direction of the body, as indicated by arrows 31.

If the frequency of the input voltage V _in applied to the pair of input terminals 11a and 11b is equal to the resonance vibration frequency in the longitudinal direction of the body, the piezoelectric transformer body is subjected to resonance vibration. Therefore, an alternating current (AC) voltage V _out is obtained between the output terminals 12a and 12b. The frequency of the output voltage V _out is equal to the frequency of the input voltage V _in .

Since the piezoelectric transformer has a square shape, it has a problem that mechanical strength is easily broken unless it has a certain thickness by concentrating strong mechanical stress at each corner portion. Therefore, the manufacturing cost of the piezoelectric transformer can be increased and the reliability can be lowered due to mechanical breakdown. In addition, the conventional piezoelectric transformer uses the bottom as a common ground for input and output, resulting in a decrease in the vibration speed (displacement) of the input stage that greatly influences the output of the piezoelectric transformer, thereby ultimately causing a decrease in output. In addition, as piezoelectric transformers are applied to high power applications, temperature loss due to vibration loss and joule heat has been pointed out as a big problem, and there is a big limitation in commercialization.

The present invention is to solve the problems as described above, the first object of the present invention is the composition formula xPbZrO ₃ + yPbTiO ₃ + zPbMn _1/3 Nb _1/3 Sb _1/3 O ₃ (where 0.38 ≤ x ≤ 0.51 Mole, 0.40 ≦ y ≦ 0.51mol, 0.05 ≦ z ≦ 0.15mol), or a piezoelectric ceramic composition comprising aCr ₂ O ₃ , aNb ₂ O ₅ , aNiO, aMnO ₂ , aMgO, or aFe as an auxiliary component. _A high mechanical quality factor (Q _m ), an electromechanical coupling factor (k _p ), a high piezoelectric strain constant, further comprising ₂ 0 ₃ (where 0 ≦ a ≦ 1 wt% based on the weight of the principal component) d ₃₃ ), to provide a piezoelectric ceramic composition for a high power piezoelectric device having a high Curie temperature and temperature stability.

The second purpose is to solve the problems of the conventional piezoelectric transformer as described above, to form a ring-shaped electrode and a disk electrode on the upper surface of the piezoelectric transformer body of the disc shape, the bottom of the piezoelectric transformer body is a whole electrode The present invention provides a piezoelectric transformer for a fluorescent lamp ballast that can adjust the step-up ratio by varying the area of the ring-shaped electrode and the disc-shaped electrode on the upper surface of the piezoelectric transformer. Instead, it provides a method of driving a piezoelectric transformer that can improve the output capacity by using the upper surface as a common ground.

1 is a schematic plan view of a conventional piezoelectric transformer,

2 is a schematic bottom view of a conventional piezoelectric transformer,

3 is a schematic front view of a conventional piezoelectric transformer,

4 is a schematic plan view of a piezoelectric transformer according to an embodiment of the present invention;

5 is a schematic bottom view of a piezoelectric transformer according to an embodiment of the present invention;

6 is a schematic front view of a piezoelectric transformer according to an embodiment of the present invention;

7 is a front view showing a piezoelectric transformer driving method according to an embodiment of the present invention,

8 is a front view showing a piezoelectric transformer driving method according to another embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

1: first electrode on the top, 2: second electrode on the top,

3: piezoelectric body, 4: bottom electrode,

5: ring-shaped electrode, 6: disc-shaped electrode,

7: piezoelectric body, 8: bottom electrode,

11a, 11b, 13a, 13b, 15a, 15b: input terminal,

12a, 12b, 14a, 14b, 16a, 16b: output terminal,

21, 22, 23: Common ground between input and output terminals.

In order to achieve the above technical problem of the first object, the piezoelectric ceramic composition of the present invention is a composition xPbZrO ₃ + yPbTiO ₃ + zPbMn _1/3 Nb _1/3 Sb _1/3 O ₃ (where 0.38 ≤ x ≤ 0.51 mol , 0.40 ≦ y ≦ 0.51 mole, 0.05 ≦ z ≦ 0.15 mole), as a main component.

In the piezoelectric ceramic composition, aCr ₂ O ₃ , aNb ₂ O ₅ , aNiO, aMnO ₂ , aMgO or aFe ₂ O ₃ as an auxiliary component (where 0 ≦ a ≦ 1 wt% based on the weight of the main component) It may further include.

In addition, the piezoelectric transformer of the present invention, to achieve the technical problem of the second object, (1) using the composition of claim 1 or 2, (2) the piezoelectric transformer has a disc shape, (3) piezoelectric The thickness of the body is 1 to 3 mm, and (4) the resonant frequency is 65 to 75 kHz.

The piezoelectric transformer has (1) an electrode structure in which the top electrode of the piezoelectric transformer is divided into a ring type and a disc type electrode, and the bottom is composed of one electrode, and (2) a ring type electrode area (A) and a disc type electrode area (B). It is preferable that ratio (A / B) of () is 0.8-10. The reason for limiting the ratio of the ring-shaped electrode area and the disk-shaped electrode area to 0.8 to 10 as described above is to achieve the desired effect of the present invention.

In addition, the driving method of the piezoelectric transformer of the present invention is characterized in that one of the divided electrodes on the upper surface of the piezoelectric transformer is used as a common ground on the input side and the output side in driving the piezoelectric transformer.

The piezoelectric ceramic composition according to the present invention is lead oxide (PbO), zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), manganese oxide (MnO), niobium oxide (Nb ₂ O ₅ ), antimony oxide (Sb ₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ) (or niobium oxide (Nb ₂ O ₅ ), nickel oxide (NiO), manganese oxide (MnO ₂ ), magnesium oxide (MgO), iron oxide (Fe ₂ O ₃₎ )) Is stoichiometrically weighed, wet mixed using a ball mill, dried using a dryer, calcined, and wet mixed and pulverized using a ball mill.

Hereinafter, a piezoelectric transformer according to the present invention will be described in detail with reference to the drawings.

4 is a schematic front view of a piezoelectric transformer having an improved electrode structure for easier understanding of the piezoelectric transformer of the present invention.

As shown, the relatively thin disc-shaped body 7 of piezoelectric material is divided into a ring-shaped electrode 5 region and a disc-shaped electrode 6 region with respect to the center of the body 7. The ring-shaped electrode 5 region is called a driving region, while the disk-shaped electrode 6 region is called a driven region. The two divided regions are polarized only in the thickness direction to simplify the manufacturing process of the piezoelectric transformer.

5 is a schematic bottom view of the piezoelectric transformer of the present invention, in which one electrode is provided. As described above, since one electrode is not used as a common ground as in the conventional piezoelectric transformer driving, the output is increased by increasing the amount of current input.

FIG. 6 is a schematic front view of the piezoelectric transformer of the present invention, with no polarization in the radial direction of a conventional piezoelectric transformer, and spaced 1 mm between the ring electrode and the disc electrode for electrical insulation. This design minimizes the reduction in efficiency due to the difference in the resonance vibration frequency in the thickness direction and the radial direction, and simplifies the manufacturing process of the piezoelectric transformer.

The driving method of the piezoelectric transformer of the present invention is characterized by using one of the divided electrodes on the upper surface of the piezoelectric transformer as the common ground as the common ground of the input side and the output side. That is, a ring-shaped electrode or a disk-shaped electrode on the upper side is used as a common ground on the input side and the output side.

7 is a driving method of the piezoelectric transformer of the present invention, and as shown in the drawing, in order to eliminate a reduction in input current generated by using a bottom as a common ground in a conventional method of driving a piezoelectric transformer, the ring-shaped electrode on the top is connected to a common ground. It was intended to increase the output by using.

FIG. 8 is a modification of the driving method of the piezoelectric transformer of FIG. 7 and is intended to increase output by using a disk-shaped electrode on the upper surface as a common ground.

The ring electrode 5 which is a driving region has input terminals 13a and 13b which are a pair of electrodes applied to the upper and lower surfaces of the ring electrode 5. The connecting line 22 provided on the ring-shaped electrode on the upper surface is used as a common ground of the input terminal and the output terminal.

The driven region has a disk-shaped electrode 6 provided on the upper surface of this region. The ground of the driven region forms a common ground together with the connecting line 22 provided on the ring-shaped electrode on the upper surface of the driven region.

Hereinafter, a representative embodiment of the piezoelectric ceramic composition of the present invention and a piezoelectric transformer manufactured using the same will be described. However, these examples are merely for illustrative purposes, the present invention is not limited thereto.

[Example of Piezoelectric Ceramic Composition]

Lead oxide (PbO), zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), manganese oxide (MnO), niobium oxide (Nb ₂ O ₅ ), antimony oxide (Sb ₂ ) so as to have the composition shown in Table 1 below. O ₃ ), chromium oxide (Cr ₂ O ₃ ) (or niobium oxide (Nb ₂ O ₅ ), nickel oxide (NiO), manganese oxide (MnO ₂ ), magnesium oxide (MgO), iron oxide (Fe ₂ O ₃₎ )) Was stoichiometrically weighed, wet mixed using a ball mill, dried using a dryer, calcined at 750 ° C. for 2 hours, and wet mixed and pulverized using a ball mill again. PVA (PolyVinyl Alcohol) binder was added to the pulverized powder, and dried. Then, the powder was placed in a cylindrical molder having a diameter of 15 mm and 36 mm, and pressurized under a pressure of 2 ton / cm ² . The molded body was sintered at 1100 to 1300 ° C for 1 to 3 hours.

Physical properties of the piezoelectric ceramic manufactured as described above are as follows.

The sintered body 12 mm in diameter as described above is patterned with silver paste on both surfaces to form a silver electrode, and a DC voltage of 2 kV / mm is applied in silicon oil for 10 to 30 minutes. The IRE standard, which is a method commonly used in the technical field, belongs to the electromechanical coefficient (k _p ), mechanical quality factor (Q _m ), dielectric constant (ε ^T ₃₃ / ε ₀ ), and piezoelectric constant (d) of each composition. ₃₃ ) was measured, respectively, and the result shown in Table 1 was obtained.

Table 1

[Example of Piezoelectric Transformer]

Using the piezoelectric ceramic composition having the excellent piezoelectricity, the powder was placed in a cylindrical molder having a diameter of 40 mm ψ in the same manner as in the above-described manufacturing method, and then sintered and polished on both sides with a thickness of 1 to 3 mm. The piezoelectric ceramic body manufactured as described above was formed by using a silk screen method to form a ring-shaped and disk-shaped electrode on the upper surface and one electrode on the lower surface thereof, and then fired at 600 ° C. Thereafter, polarization was performed with a direct current field of 2 kV / mm from the top surface to the bottom surface direction. The piezoelectric transformer manufactured as described above was soldered to the ring-shaped electrode, the disk-shaped electrode and the lower electrode of the upper surface by soldering.

<Example 1>

In this embodiment, xPbZrO ₃ + yPbTiO ₃ + zPbMn _1/3 Nb _1/3 Sb _1/3 O ₃ + aNb ₂ O ₅ (x = 0.48 mol, y = 0.47 mol, z = 0.05 mol, a = 0.5 wt% A piezoelectric transformer was manufactured by the above method using a piezoelectric ceramic composition (sintered at 1180 ° C.). The ratio (A / B) of the ring-shaped electrode area (A) and the disk-shaped electrode area (B) of the disk-shaped piezoelectric transformer was set to 10, and the ring-shaped electrode was used as a common ground on the input side and the output side. At this time, the load of the piezoelectric transformer used a 32W fluorescent lamp, the thickness was 1mm. When the input voltage was 50 V, the voltage across the lamp was 170 V, the lamp current was 150 mA, and the resonance frequency was 65 kHz after the fluorescent lamp was turned on.

<Example 2>

xPbZrO ₃ + yPbTiO ₃ + zPbMn _1/3 Nb _1/3 Sb _1/3 O ₃ + aNb ₂ O ₅ (x = 0.48 moles, y = 0.47 moles, z = 0.05 moles, a = 0.5 wt%) A piezoelectric transformer was manufactured by the above method using a piezoelectric ceramic composition (sintered at 1180 ° C.). The ratio (A / B) of the ring-shaped electrode area (A) and the disk-shaped electrode area (B) of the disk-shaped piezoelectric transformer was 5, and the ring-shaped electrode was used as a common ground on the input side and the output side. At this time, the load of the piezoelectric transformer used a 32W fluorescent lamp, the thickness was 1mm. When the input voltage was 100 V, the voltage across the lamp was 160 V, the lamp current was 170 mA, and the resonance frequency was 70 kHz after the fluorescent lamp was turned on.

<Example 3>

xPbZrO ₃ + yPbTiO ₃ + zPbMn _1/3 Nb _1/3 Sb _1/3 O ₃ + aNb ₂ O ₅ (x = 0.48 moles, y = 0.47 moles, z = 0.05 moles, a = 0.5 wt%) A piezoelectric transformer was manufactured by the above method using a piezoelectric ceramic composition (sintered at 1180 ° C.). The ratio (A / B) of the ring-shaped electrode area (A) and the disk-shaped electrode area (B) of the disk-shaped piezoelectric transformer was 1, and the ring-shaped electrode was used as a common ground on the input side and the output side. At this time, the load of the piezoelectric transformer used a 32W fluorescent lamp, the thickness was 1mm. When the input voltage was 150 V, the voltage across the lamp was 150 V, the lamp current was 200 mA, and the resonance frequency was 75 kHz after the fluorescent lamp was turned on.

<Example 4>

xPbZrO ₃ + yPbTiO ₃ + zPbMn _1/3 Nb _1/3 Sb _1/3 O ₃ + aNb ₂ O ₅ (x = 0.48 moles, y = 0.47 moles, z = 0.05 moles, a = 0.5 wt%) A piezoelectric transformer was manufactured by the above method using a piezoelectric ceramic composition (sintered at 1180 ° C.). The ratio (A / B) of the ring-shaped electrode area (A) and the disk-shaped electrode area (B) of the disk-shaped piezoelectric transformer was 0.8, and the ring-shaped electrode was used as a common ground on the input side and the output side. At this time, the load of the piezoelectric transformer used a 32W fluorescent lamp, the thickness was 1mm. When the input voltage was 170V, the voltage across the lamp was 150V, the lamp current was 210mA, and the resonance frequency was 77kHz after the fluorescent lamp was turned on.

Example 5

xPbZrO ₃ + yPbTiO ₃ + zPbMn _1/3 Nb _1/3 Sb _1/3 O ₃ + aNb ₂ O ₅ (x = 0.48 moles, y = 0.47 moles, z = 0.05 moles, a = 0.5 wt%) A piezoelectric transformer was manufactured by the above method using a piezoelectric ceramic composition (sintered at 1180 ° C.). The ratio (A / B) of the ring-shaped electrode area (A) and the disk-shaped electrode area (B) of the disk-shaped piezoelectric transformer was 1, and the ring-shaped electrode was used as a common ground on the input side and the output side. At this time, the load of the piezoelectric transformer used a 32W fluorescent lamp, the thickness is 1.5mm. When the input voltage was 150 V, the voltage across the lamp was 150 V, the lamp current was 190 mA, and the resonance frequency was 74 kHz after the fluorescent lamp was turned on.

<Example 6>

xPbZrO ₃ + yPbTiO ₃ + zPbMn _1/3 Nb _1/3 Sb _1/3 O ₃ + aNb ₂ O ₅ (x = 0.48 moles, y = 0.47 moles, z = 0.05 moles, a = 0.5 wt%) A piezoelectric transformer was manufactured by the above method using a piezoelectric ceramic composition (sintered at 1180 ° C.). It is a case where the ratio (A / B) of the ring-shaped electrode area (A) and the disk-shaped electrode area (B) of the disk-shaped piezoelectric transformer is 1, and the ring-shaped electrode is used as a common ground on the input side and the output side. At this time, the load of the piezoelectric transformer used a 32W fluorescent lamp, the thickness is 2mm. When the input voltage was 150 V, the voltage across the lamp was 160 V, the lamp current was 180 mA, and the resonance frequency was 73.5 kHz after the fluorescent lamp was turned on.

<Example 7>

xPbZrO ₃ + yPbTiO ₃ + zPbMn _1/3 Nb _1/3 Sb _1/3 O ₃ + aNb ₂ O ₅ (x = 0.48 moles, y = 0.47 moles, z = 0.05 moles, a = 0.5 wt%) A piezoelectric transformer was manufactured by the above method using a piezoelectric ceramic composition (sintered at 1180 ° C.). The ratio (A / B) of the ring-shaped electrode area (A) and the disk-shaped electrode area (B) of the disk-shaped piezoelectric transformer was set to 1, and the disk-shaped electrode was used as a common ground on the input side and the output side. At this time, the load of the piezoelectric transformer used a 32W fluorescent lamp, the thickness was 1mm. When the input voltage was 150 V, the voltage across the lamp was 200 V, the lamp current was 100 mA, and the resonance frequency was 75 kHz after the fluorescent lamp was turned on.

Comparative Example 1

xPbZrO ₃ + yPbTiO ₃ + zPbMn _1/3 Nb _1/3 Sb _1/3 O ₃ + aNb ₂ O ₅ (x = 0.48 moles, y = 0.47 moles, z = 0.05 moles, a = 0.5 wt%) A piezoelectric transformer was manufactured by the above method using a piezoelectric ceramic composition (sintered at 1180 ° C.). The ratio between the ring-shaped electrode area (A) and the disc-shaped electrode area (B) of the disk-shaped piezoelectric transformer (A / B) was 1, and the bottom electrode was used as a common ground on the input side and the output side. At this time, the load of the piezoelectric transformer used a 32W fluorescent lamp, the thickness was 1mm. When the input voltage was 150V, the voltage across the lamp was 220V, the lamp current was 80mA, and the resonance frequency was 75kHz after the fluorescent lamp was turned on.

As can be seen from the above, the piezoelectric ceramic composition according to the present invention has a high mechanical quality factor (Q _m ), an electromechanical coupling coefficient (k _p ), a high piezoelectric constant (d ₃₃ ) and a low dielectric loss (tanδ). , Has high Curie temperature and temperature stability. In addition, by using the improved piezoelectric transformer and its driving method using the composition, it is possible to prevent the concentration of mechanical stress compared to the conventional piezoelectric transformer, thereby increasing reliability against mechanical breakdown, and to make the polarization of the piezoelectric transformer only in the thickness direction. It is possible to achieve the effect of reducing raw materials by simplifying the manufacturing process of the piezoelectric body and making the thickness of the piezoelectric body 1 to 3 mm, and greatly improving the output capacity by reducing the area of the common ground.

Claims (5)

The formula xPbZrO ₃ + yPbTiO ₃ + zPbMn _1/3 Nb _1/3 Sb _1/3 O ₃ , wherein x, y, z are 0.38 ≦ x ≦ 0.51 mol, 0.40 ≦ y ≦ 0.51 mol, 0.05 ≦ z A piezoelectric ceramic composition comprising as a main component a compound of? The method of claim 1, wherein aCr ₂ O ₃ , aNb ₂ O ₅ , aNiO, aMnO ₂ , aMgO or aFe ₂ O ₃ , wherein a is 0 ≦ a ≦ 1 based on the weight of the main component. A piezoelectric ceramic composition, further comprising a weight% compound as an auxiliary component. (1) using the composition of claim 1 or 2, (2) the piezoelectric transformer is disc-shaped; (3) the piezoelectric body has a thickness of 1 to 3 mm, (4) A piezoelectric transformer whose resonance frequency is 65 to 75 kHz. The method of claim 3, (1) the upper electrode of the piezoelectric transformer is divided into a ring-shaped and a disk-shaped electrode, and the bottom has an electrode structure consisting of one electrode, (2) A piezoelectric transformer, characterized in that the ratio (A / B) of the ring-shaped electrode area A and the disk-shaped electrode area B is in the range of 0.8 to 10. 5. A method of driving a piezoelectric transformer according to claim 3 or 4, wherein one of the divided electrodes on the upper surface of the piezoelectric transformer is used as a common ground on the input side and the output side.