JP2002356372A - Piezoelectric ceramic composition and piezoelectric transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric composition and a piezoelectric transformer which is excellent in temperature stability in resonance frequency while keeping high an electromechanical coupling coefficient Kp, and a mechanical quality coefficient Qm. SOLUTION: The composition is a composite oxide of perovskite type containing Pb, Zr, Ti, Nb, Mn, and Fe, as metal elements, and at least one element among Gd, Sm, and Sm, the composition formula of which is represented in molar ratio of metal elements as follows: (Pb(1-a)x Ra ) [(Nb1-c-f Mnc Fef )b Mnc (Tid Zr1-d )1-b-c ]O3 (wherein, R is at least one element among Gd, Sm, and Nd). The above described numbers a, b, c, d, and x satisfy the following conditions: 0.005<=a<=0.025, 0.07<=b<=0.14, 0<c<=0.02, 0.50<d<=0.55, and 0.98<=x<=1.02.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric ceramic composition and a piezoelectric transformer, and more particularly to an AC adapter and a DC-DC converter used for various electronic devices, and a notebook computer and a portable terminal. The present invention relates to a piezoelectric ceramic composition and a piezoelectric transformer suitable for a piezoelectric transformer used for an inverter for a backlight cold-cathode tube of a liquid crystal display.

[0002]

2. Description of the Related Art Conventionally, piezoelectric ceramic compositions containing Pb, Zr, Ti and O include, for example, PbZrO ₃ -P
a two-component material such as a bTiO ₃ material or Pb (Nb _{2/3
Mn 1/3) O 3 -PbZrO} 3 -PbTiO 3 system three-component material, such as material, or the like such materials is added to the materials of various dopants on the system are known.

[0003] These materials have excellent piezoelectric properties,
It is excellent in workability and mass productivity, and its application range is wide, including resonators, actuators and piezoelectric sensors. In recent years, attempts have been made to configure a transformer, which has conventionally been configured with a coil, with a piezoelectric element.

[0004] The piezoelectric transformer is capable of reversible conversion between an AC signal and elastic vibration, and the conversion efficiency depends on the mechanical quality factor Qm and the electromechanical coupling factor Kp of the porcelain material. Also,
Since high power can be output by driving at a frequency close to the resonance frequency, it is necessary to suppress the resonance frequency from fluctuating due to self-heating and from fluctuating due to the outer peripheral temperature.

Since the step-up / step-down ratio between the input voltage V1 and the output voltage V2 is calculated by the equation (V2 / V1) = (C1 / C2) ^1/2 , (V2 / V1 is the step-up / step-down ratio and C1 is the voltage The capacitance of the input unit, C2 is the capacitance of the voltage output unit), the voltage input unit and / or the voltage output unit must have a laminated structure and have a predetermined capacitance ratio.

Conventionally, piezoelectric ceramic compositions having a large mechanical quality factor Qm and a large electromechanical coupling factor Kp include Pb (Nb
_2/3 Mn _1/3 ) O ₃ —PbZrO ₃ —PbTiO ₃ as a main component or a piezoelectric ceramic composition containing Pb (Nb _1/2 Sb _1/2 ) O ₃
A piezoelectric ceramic composition containing -PbZrO ₃ -PbTiO ₃ as a main component is known.

[0007]

However, in the piezoelectric ceramic composition described above, when the mechanical quality factor Qm is increased, the electromechanical coupling factor Kp is reduced. Couldn't be larger. On the other hand, when the electromechanical coupling coefficient Kp is increased, there is a problem that the mechanical quality coefficient Qm decreases and, in addition, the temperature stability of the resonance frequency also deteriorates.

An object of the present invention is to provide a piezoelectric ceramic composition and a piezoelectric transformer excellent in temperature stability of a resonance frequency while maintaining a high electromechanical coupling coefficient Kp and a high mechanical quality coefficient Qm.

[0009]

The piezoelectric ceramic composition of the present invention comprises a perovskite-type composite oxide containing Pb, Zr, Ti, Nb, Mn and Fe as metal elements and at least one of Gd, Sm and Nd. And the composition formula based on the molar ratio of the metal elements is (Pb _{(1-a) x Ra} ) [(Nb
_{1-ef Mn e Fe f)} b Mn c (Ti d Zr 1-d) 1-b - c ] O ₃
(Where R is at least one of Gd, Sm, and Nd), the values of a, b, c, d, and x are not more than 0.
005 ≦ a ≦ 0.025, 0.07 ≦ b ≦ 0.14, 0
<C ≦ 0.02, 0.50 <d ≦ 0.55, 0.98 ≦
It satisfies x ≦ 1.02.

In such a piezoelectric ceramic composition, the temperature stability of the resonance frequency can be improved by replacing the A site of the perovskite-type composite oxide with Gd, Sm, and Nd. On the other hand, the substitution of Gd, Sm, and Nd lowers the Curie temperature Tc and easily lowers the mechanical quality factor Qm. However, the B site of PZT is usually tetravalent, but the divalent to tetravalent B site is usually used. By substituting a predetermined amount with Mn, it is possible to suppress a decrease in the Curie temperature Tc and the mechanical quality factor Qm.

Therefore, the piezoelectric ceramic composition of the present invention can improve the temperature stability of the resonance frequency while maintaining the electromechanical coupling coefficient Kp and the mechanical quality coefficient Qm high.

Further, in the piezoelectric transformer of the present invention, voltage input portions and voltage output portions are alternately formed in the length direction of the piezoelectric substrate whose both main surfaces are rectangular and have a length L and a width W. In a piezoelectric transformer in which an input side electrode and an output side electrode are provided in a unit and a voltage output unit, respectively, the piezoelectric layer of the piezoelectric substrate is made of the piezoelectric ceramic composition described above.

As described above, the piezoelectric ceramic composition of the present invention can improve the temperature stability of the resonance frequency while maintaining the electromechanical coupling coefficient Kp and the mechanical quality coefficient Qm high. When the piezoelectric layer is composed of the composition, high output power and high efficiency can be stably obtained without drastically changing the driving frequency.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The piezoelectric ceramic composition of the present invention comprises Pb, Zr, Ti, Nb, Mn and Fe as metal elements.
Gd, a perovskite complex oxide containing at least one of Sm and Nd, the composition formula by molar ratio of the metal elements _{(Pb (1-a) x} R a) [(Nb _1-ef Mn _{e
Fe f) b Mn c (Ti} d Zr 1-d) 1-b - c ] O ₃ (Here, R
Is at least one of Gd, Sm and Nd), a, b, c, d and x are 0.005 ≦ a ≦ 0.
025, 0.07 ≦ b ≦ 0.14, 0 <c ≦ 0.02,
0.50 <d ≦ 0.55 and 0.98 ≦ x ≦ 1.02 are satisfied.

Here, the substitution amount a of Pb by at least one of Gd, Sm and Nd is 0.005 ≦ a ≦
The reason for setting 0.025 is that Gd, Sm, N
d has the effect of improving the temperature stability of the resonance frequency in particular, but the A-site substitution amount a of Gd, Sm, and Nd is 0.0%.
If it is less than 05, there is no substitution effect, and if it exceeds 0.025, the Curie temperature Tc is lowered, and the mechanical quality factor Qm is lowered.

The substitution amount a of Pb with at least one of Gd, Sm, and Nd is set at 0.1 from the viewpoint that the temperature stability of the resonance frequency can be improved, and the Curie temperature Tc and the mechanical quality factor Qm are kept high. 01 ≦ a ≦ 0.
02 is desirable.

In the present invention, at least one of Gd, Sm, and Nd is used as a rare earth element that substitutes for Pb. Since the characteristics, particularly the electromechanical coupling coefficient Kp, are greatly reduced, at least one selected from Gd, Sm, and Nd is used.

As a rare earth element that substitutes for Pb, Gd or Gd is used in view of maintaining a high mechanical coupling coefficient Kp.
d and Sm and / or Nd are desirable.

The B-site was a _{(Nb 1-ef Mn e Fe} f) 0.07 ≦ b ≦ 0.14 substitution amount b due replaces the B site of the perovskite ABO ₃ (Nb _1-ef M
n _e Fe _f) is possible in particular improved electromechanical coupling factor Kp and the mechanical quality factor Qm, not sufficient displacement effect is obtained when the substitution amount b is less than 0.07, greater than 0.14 In this case, a dense porcelain cannot be obtained, and the mechanical quality factor Qm decreases.

The substitution amount b by _{(Nb 1-ef Mn e Fe} f) of B site, as well as improve the electromechanical coupling factor Kp and mechanical quality factor Qm, from the viewpoint that it is possible to obtain a dense porcelain, It is desirable that 0.09 ≦ b ≦ 0.12.

The substitution amount c of the B site with Mn is 0 <c ≦
The reason for setting the value to 0.02 is that Mn replacing the B site is effective for improving the mechanical quality factor Qm, but when the amount c of Mn replacement exceeds 0.02, a dense porcelain cannot be obtained. This is because the mechanical quality factor Qm decreases. Mn of B site
Is 0.005 ≦ c ≦ 0.01 from the viewpoint of improving the mechanical quality factor Qm and obtaining a dense porcelain.
5 is desirable.

The Ti / (Ti + Zr) ratio d is set to 0.5
The reason for setting 0 <d ≦ 0.55 is that the Ti / (Ti + Zr) ratio d has the effect of improving the temperature stability of the resonance frequency in addition to the effect of improving the mechanical quality coefficient Qm and the electromechanical coupling coefficient Kp. However, if the Ti / (Ti + Zr) ratio d is 0.5 or less, the temperature stability of the resonance frequency is poor, and 0.55
Is exceeded, the electromechanical coupling coefficient Kp decreases. The Ti / (Ti + Zr) ratio d is the mechanical quality factor Q
From the viewpoint of improving the temperature stability of m, the electromechanical coupling coefficient Kp, and the resonance frequency, 0.51 ≦ d ≦ 0.53 is desirable.

The Pb correction ratio x is set to 0.98 ≦ x ≦ 1.
02 because the Pb correction ratio x is particularly the mechanical quality factor Q
m, but the Pb correction ratio x is 0.98
If it is less than 1.0, it is not possible to obtain sufficient piezoelectricity because a dense porcelain cannot be obtained, and if it exceeds 1.02, the effect of addition is small. It is desirable that the Pb correction ratio x satisfies 0.99 ≦ x ≦ 1.01 from the viewpoint of improving the mechanical quality factor Qm and obtaining a dense porcelain.

In the piezoelectric ceramic composition of the present invention, B
Substituting site _{(Nb 1-ef Mn e Fe} f) Mn amount e, Fe amount f in is, 0.11 ≦ e ≦ 0.20,0.20 ≦
It is desirable that f ≦ 0.33.

This is because the amount of Mn e is 0.11 ≦ e ≦ 0.2
0 and was of the, Mn substitution amount in _{(Nb 1-ef Mn e Fe} f) has the effect of increasing the mechanical quality factor Qm, if e is less than 0.11, the addition This is because the effect cannot be obtained, while when it is larger than 0.2, the Curie temperature tends to decrease. e preferably satisfies 0.15 ≦ e ≦ 0.18 from the viewpoint of increasing the mechanical quality factor Qm and keeping the Curie temperature high.

Further, the Fe amount f is set to 0.20 ≦ f ≦ 0.33
The reason is that (Nb_1-efMn_eFe _fFe substitution amount in)
Has the effect of increasing the mechanical quality factor Qm
However, when f is smaller than 0.20, the effect of addition is obtained.
On the other hand, when it is larger than 0.33,
And the mechanical quality factor Qm tends to decrease.
It is. f says to keep the mechanical quality factor Qm high
From the viewpoint, it is desirable that 0.24 ≦ e ≦ 0.28.
No.

The piezoelectric ceramic composition of the present invention, the composition formula by molar ratio _{(Pb (1-a) x} R a) _{[(Nb 1-ef Mn e Fe} f)
_{b Mn c (Ti d Zr 1} -d) 1-b - c ] O ₃ (where, R represents G
When expressed as d), a, b, c, d and x are 0.01
≦ a ≦ 0.02, 0.09 ≦ b ≦ 0.12, 0.005
≤c≤0.015, 0.51≤d≤0.53, 0.99
≦ x ≦ 1.01 and 0.13 ≦ e ≦
It is most desirable to satisfy 0.2, 0.24 ≦ f ≦ 0.28.

First, such a piezoelectric ceramic composition is prepared by using PbO, TiO ₂ , ZrO ₂ , Nb ₂ O ₅ , F
e ₂ O ₃ , MnO ₂ , Gd ₂ O ₃ , Nd ₂ O ₃ , Sm ₂ O
Each powder ₃ were wet-mixed in a predetermined ratio, discharge, and dried after sizing, it was placed in made of Al ₂ O ₃ crucible or the like, 800-100
The mixture is calcined at a temperature of 0 ° C. for 3 to 5 hours and crushed to obtain a calcined powder.

The raw material powder to be used is not limited to carbonates and oxides, and may be any compound such as acetate or organic metal as long as it becomes an oxide by a heat treatment process such as firing. Absent.

An organic binder is mixed with the powder, molded into a desired shape by a mold press, an isostatic press, or the like, and then, in an oxygen-containing atmosphere such as air, 1000 to 1000
Porcelain can be obtained by firing at 1200 ° C. for 2 to 5 hours.

The obtained porcelain is almost (Pb _{(1-a) x} R _a )
_{[(Nb 1-ef Mn e Fe} f) b Mn c (Ti d Zr 1-d) 1-b
_- it consists only of crystal grains containing the perovskite-type composite oxide represented by _c] O _3. ZrO _{2 at} grain boundary
There is a case where a small amount of particles containing as a main component precipitate, but there is no problem as long as the characteristics are not affected.

In the case of porcelain, unavoidable impurities such as Rb, Hf, Si, Al, Sb, Bi, and Ag diffused from the internal electrode of the laminated body into the inside of the porcelain may be mixed in a small amount in the raw material powder. There is, however, no problem as long as the characteristics are not affected.

In the piezoelectric ceramic composition as described above, the A site of the perovskite-type composite oxide is changed to Gd, Sm, Nd
, The temperature stability (temperature change rate) of the resonance frequency can be improved to within ± 0.1% at −20 ° C. to 80 ° C. On the other hand, although the Curie temperature Tc tends to decrease due to the substitution of Gd, Sm, and Nd, the PZT
The B site of the system is tetravalent, but by substituting a predetermined amount with divalent to tetravalent Mn, the Curie temperature Tc becomes 280 ° C.
And the mechanical quality factor Qm can be 900 or more.

FIG. 1 shows a single-plate type piezoelectric transformer according to the present invention. As shown in FIG. 1, the single-plate type piezoelectric transformer is polarized in a thickness direction, and has a first voltage input portion A1 in a length direction of a rectangular piezoelectric substrate 11 having a main surface having a length L and a width W. , A voltage output section B1 and a second voltage input section C1 are sequentially formed.

An input electrode 12, an output electrode 14, and an input electrode 13 are provided on the upper main surface of the piezoelectric substrate 11 in the first voltage input section A1, the voltage output section B1, and the second voltage input section C1. Each of these electrodes 1
2, 13, and 14 are formed at predetermined intervals in the length direction of the piezoelectric substrate 11. On the lower main surface of the piezoelectric substrate 11, an input-side electrode 15, an output-side electrode 17, and an input-side electrode 16 are formed at predetermined intervals in the length direction of the piezoelectric substrate 11.

That is, input-side electrodes 12 and 15 are formed on both main surfaces of the piezoelectric substrate 11 in the first voltage input portion A1, and output-side electrodes are formed on both main surfaces of the piezoelectric substrate 11 in the voltage output portion B1. 14 and 17 are formed, and the input side electrodes 1 are provided on both main surfaces of the piezoelectric substrate 11 in the second voltage input portion C1.
The electrodes 12 to 17 are formed such that one side has the same length as the width W of the main surface of the piezoelectric substrate 11, and the other side has an arbitrary length in the length direction of the main surface, for example, L1, L2. , L3
It has been.

The input electrode 12 and the input electrode 15 have the same dimensions, the output electrode 14 and the output electrode 17 have the same dimensions, and the input electrode 13 and the input electrode 16 have the same dimensions. I have. The piezoelectric substrate 11 is formed of the piezoelectric ceramic composition described above.

In the piezoelectric transformer of the present invention, the ratio (L / W) of the length L to the width W of the main surface of the piezoelectric substrate 11 is 1.1.
It is desirably about 1.4. By setting the ratio (L / W) of the length L and the width W of the main surface of the piezoelectric substrate 11 to 1.1 to 1.4, high energy conversion efficiency can be achieved.

In the piezoelectric transformer of the present invention, the product of the length L of the main surface of the piezoelectric substrate 11 and the driving frequency F (F × L)
Is set to 4700 to 6000 kHz · mm.

In the present invention, the length L of the main surface of the piezoelectric substrate 11
By setting the ratio (L / W) of the width and the width W to 1.1 to 1.4 and selecting a predetermined driving frequency, the fundamental wave that oscillates in the length direction of the piezoelectric substrate 11 is mainly used. A combined mode vibration including vibration is generated in the piezoelectric substrate 11, and the largest vibration can be generated in the voltage output portion B1 formed in the center portion. For example, when the most excited vibration in the width direction is used. The amount of electric charge induced in the voltage output unit B1 is larger than that of the first embodiment, and high output power can be obtained.

The product (F × L) of the length L of the main surface of the piezoelectric substrate 11 and the driving frequency F is desirably 4700 to 6000 kHz · mm from the viewpoint that high output power can be obtained. Therefore, in order to obtain high output power and high efficiency,
L / W is set to 1.1 to 1.4, and F × L is set to 4700 to 60.
It is desirable to be 00 kHz · mm.

According to the present invention, by setting the product (F × L) of the driving frequency F and the length L of the main surface in the above-described structure in a predetermined range, high energy conversion efficiency and high input power can be obtained. A piezoelectric transformer with high output power and high efficiency that can be used at a voltage can be realized.

FIG. 2 shows a multi-layer piezoelectric transformer according to the present invention.
A first voltage input portion A2, a voltage output portion B2, and a second voltage input portion C are provided on a rectangular piezoelectric substrate 21 having a width W in the longitudinal direction.
2 are sequentially formed.

An input side electrode 22a, an output side electrode 24a, and an input side electrode 23a are provided on the upper main surface of the piezoelectric substrate 21 in the first voltage input section A2, the voltage output section B2, and the second voltage input section C2. The electrodes 22a, 23a, and 24a are formed at predetermined intervals in the length direction of the piezoelectric substrate 21. Also, the piezoelectric substrate 2
1, the input side electrode 22d, the output side electrode 2
4j and input-side electrodes 23d are formed at predetermined intervals in the length direction of the piezoelectric substrate 21.

The piezoelectric substrate 21 in the first voltage input section A2
, Input-side electrodes 22b and 22c are formed inside the piezoelectric substrate 21 in the voltage output unit B2, and output-side electrodes 24b to 24i are formed inside the piezoelectric substrate 21 in the voltage output unit B2. Have input electrodes 23b, 2
3c is formed.

The input electrodes 22a to 22d have the same dimensions, the output electrodes 24a to 24j have the same dimensions, and the input electrodes 23a to 23d have the same dimensions. The input side electrodes 22a and 23a and the output side electrode 24a
The input side electrodes 22 b and 23 b and the output side electrode 24 d are provided on the same plane inside the piezoelectric substrate 21, and the input side electrodes 22 b
c, 23c and an output-side electrode 24g are provided on the same plane inside the piezoelectric substrate 21.
d, 23 d and an output-side electrode 24 j are provided on the same plane on the lower main surface of the piezoelectric substrate 21. Note that the output side electrodes in FIG.

The input side electrodes 22a to 22d are
1 pair of external electrodes 25a1, 25 formed on both side surfaces
a2, the output side electrodes 24a to 24j
Are alternately connected by a pair of external electrodes 25b1 and 25b2, and the input-side electrodes 23a to 23d are
They are connected alternately by c1 and 25c2.

Also in this piezoelectric transformer, as in the piezoelectric transformer shown in FIG. 1, the ratio (L / W) of the length L to the width W of the main surface of the piezoelectric substrate 21 is 1.1 to 1.4. Yes,
In addition, it is desirable that the product (F × L) of the length L of the main surface of the piezoelectric substrate 21 and the driving frequency F is 4700 to 6000 kHz · mm. The ratio (L / W) of the length L to the width W of the main surface of the piezoelectric substrate 21 and the ratio (L / W) of the length L to the width W of the main surface of the piezoelectric substrate.
The reason why W) was set to the predetermined range, particularly a preferable range is as follows.
Same as above. The piezoelectric substrate 21 is also formed from the piezoelectric ceramic composition described above.

In such a laminated piezoelectric transformer, FIG.
Although the same effect as the piezoelectric transformer shown in FIG. 2 can be obtained, the multilayer piezoelectric transformer shown in FIG. 2 can further increase the area of the output side electrode, and thus can be compared with a single-plate piezoelectric transformer having the same length and width. A large output current can be obtained.

The voltage step-up / step-down ratio (= V2 / V1) of the piezoelectric transformer is given by V2 / V1∝ (Cd1 / Cd1 / Cd1) where Cd1 is the input-side capacitance and Cd2 is the output-side capacitance.
Since Cd2) ^1/2 , Cd1 and Cd2 can be controlled by stacking piezoelectric transformers, and the step-up / step-down ratio can be set arbitrarily. That is, the piezoelectric transformer of the present invention
By arbitrarily determining the buck-boost ratio, the buck-boost converter can be suitably used for a buck-boost converter or a buck-boost inverter.
Note that the voltage input section may not have the internal electrode.

A method for manufacturing such a piezoelectric transformer will be described. The piezoelectric substrate of the present invention uses a piezoelectric material,
A ceramic green sheet having a desired thickness is manufactured by a doctor blade method, a calendaring method, or the like.

Next, a high heat-resistant conductive paste such as an Ag-Pd paste is screen-printed on one side of the ceramic green sheet. In this case, a green sheet on which a pattern serving as an input-side electrode and a pattern serving as an output-side electrode are formed, and a green sheet on which only a pattern serving as an output-side electrode is formed. Crimped by an inter-press, integrated, 4
After heating at 00 to 500 ° C to perform degreasing, 1100 to
By firing at a temperature of 1300 ° C. for 2 to 4 hours, a laminated ceramic can be obtained.

Next, a conductive paste is applied to both sides of the sintered body as external electrodes. The input electrodes 22a to 22d are alternately connected to each other by a pair of external electrodes 25a1 and 25a2. The output electrodes 24a to 24j are alternately connected to each other by a pair of external electrodes 25b1 and 25b2. Further, the input-side electrodes 23a to 23d are alternately connected by a pair of external electrodes 25c1 and 25c2. That is, the input-side electrode and the output-side electrode have a structure like a multilayer capacitor or a multilayer piezoelectric actuator, and the internal electrodes are connected alternately by the external electrodes.

Next, the input side electrodes 22a to 22d, 23a to 23d and the output side electrodes 24a to 24j formed on both main surfaces of the obtained laminate are respectively applied with insulating oil at 80 to 200 ° C. A piezoelectric field is obtained by applying a DC electric field of 0.0 to 5.0 kV / mm for 10 to 60 minutes to perform polarization processing.

In the piezoelectric transformer of the present invention, the output power 20
Excellent characteristics of W or more and efficiency of 85% or more can be obtained.

[0056]

EXAMPLE 1 PbO, ZrO ₂ , Ti as powder as starting materials
O ₂ , Nb ₂ O ₅ , MnO ₂ , Fe ₂ O ₃ , Gd ₂ O ₃ , Sm ₂
The respective raw material powders of O ₃ and Nd ₂ O ₃ were prepared by a composition formula (Pb _{(1-a) x Ra} ) [(Nb _0.58 Mn _0.17 Fe _0.25 ) _b M
_{n c (Ti d Zr 1-} d) 1-b - In _c] O _3, to d shown in Table 1, x, were weighed in predetermined amounts so that R.

The raw material powder was weighed, wet-mixed using a ₃ mmφ ZrO ₂ ball for 20 hours, discharged, dried, sized, put into an Al ₂ O ₃ crucible, and temporarily heated at a temperature of 950 ° C. for 3 hours. After baking, the calcined product was pulverized again by a ball mill.

Thereafter, an organic binder was mixed with the pulverized product and granulated. The obtained powder was press-formed at a pressure of 150 MPa into a square plate having a length of 37 mm, a width of 25 mm, and a thickness of 2 mm. Furthermore, these compacts are
The container was sealed in a container made of gO or the like, and fired in the air at a temperature of 1200 ° C. for 2 hours.

The obtained sintered body was polished to a thickness of 1.0 mm.
An electrode paste containing silver and glass as main components was applied to both surfaces of the square plate and baked. In addition, 20
A polarization treatment was performed by applying a DC electric field of 1.1 kV / mm in silicon oil at 0 ° C. for 30 minutes.

After that, the square plate is 3 mm wide × 12 mm long.
Excision of the shape, the evaluation of the electromechanical coupling factor k ₃₁ and a mechanical quality factor Qm was performed by a resonance-antiresonance method. The sample size described above is based on EMAS6001.
The measuring device is an impedance analyzer (agi).
Rent4294A) was used.

The temperature stability of the resonance frequency is -20 ° C., 2
Measure the resonance frequency of 5 ° C and 80 ° C, and measure the temperature stability fr _{TC
= (Fr (- 20 ℃,} 80 ℃) -fr (25 ℃)) / fr (25 ℃) ×
It was calculated from the formula of 100 (unit:%). Table 1 shows the results.

[0062]

[Table 1]

In the sample of the present invention, the electromechanical coupling coefficient k ₃₁
25% or more, the mechanical quality factor Qm is 900 or more, and the temperature stability of the resonance frequency is within ± 0.1%. still. The Curie temperature of Sample No. 6 is 2
40 ° C. 10 was 250 ° C., whereas the sample of the present invention was 280 ° C. or higher, which was excellent in heat resistance.

The effect of increasing the electromechanical coupling coefficient k ₃₁ is due to T
The i / (Ti + Zr) ratio d is remarkable. Sample No. 4 and No. 4. As the ratio d approaches 0.5 from 16 to 20, the electromechanical coupling coefficient k ₃₁ increases, and the mechanical quality factor Q
m decreases slightly. No. within the scope of the present invention. 4 and No. 4.
17 to 19 is the electromechanical coupling coefficient k ₃₁ is 25.3 to 28.
No. 4%, the mechanical quality factor Qm was 1130 to 1240, and the temperature stability of the resonance frequency was 0.038 to 0.05%. In No. 16, the mechanical quality factor Qm was as low as 790. In No. 20, the electromechanical coupling coefficient k ₃₁ was reduced to 22.5%.

The effect of increasing the mechanical quality factor Qm is Pb
The influence of the correction ratio x and the Mn ratio c replacing the B site is remarkable. Sample No. 11 to 15 and sample No. 21-
In 25, follow reduce Pb correction ratio and the mechanical quality factor Qm in accordance with the Mn substitution of B site closer to 0.015 increases, the electromechanical coupling factor k ₃₁ becomes smaller. No. within the scope of the present invention. 12-14 or No. 22
24 is the electromechanical coupling factor k ₃₁ is 26.2 to 32.6
%, The mechanical quality factor Qm is 900 to 1200, and the temperature stability of the resonance frequency is 0.03 to 0.056%. In Nos. 11 and 25, the effect of improving the mechanical quality factor Qm was small. Electromechanical coupling factor k ₃₁ in 15 and 21 is 24.5 percent smaller and 20.0%.

The effect of improving the temperature stability of the resonance frequency is as follows.
It is remarkable that Pb is replaced with Gd, Sm, and Nd.
Sample No. In 1 to 6, Gd, Sm, according to increase the Nd substitution amount, the temperature stability of the resonant frequency is high, the electromechanical coupling factor k ₃₁ becomes smaller. No. within the scope of the present invention. 2 to 5 have an electromechanical coupling coefficient k ₃₁ of 27.3.
３１31.8%, mechanical quality factor Qm is 950 to 130
0, temperature stability of resonance frequency is 0.019 to 0.082
%, Which is out of the range of the present invention. In the case of No. 1, the effect of improving the temperature stability of the resonance frequency is small. Electromechanical coupling factor k ₃₁ in 6 becomes smaller as 19.8%. Example 2 Sample no. In the composition of 4, i.e. the composition formula by molar ratio (Pb _0.985 R _{0.015) [(Nb 1-ef Mn e Fe} f) 0.1 Mn 0.01 (Ti 0.506 Z
r _0.494 ) _0.89 ] O ₃ , a piezoelectric ceramic was prepared in the same manner as in Example 1 except that predetermined amounts were weighed so as to obtain e and f shown in Table 2, and the piezoelectric characteristics were evaluated.
The results are shown in Table 2.

[0067]

[Table 2]

From Table 2, it can be seen that, in the above composition formula, 0.1.
When 11 ≦ e ≦ 0.20 and 0.20 ≦ f ≦ 0.33 are satisfied, a high electromechanical coupling coefficient k ₃₁ and a high mechanical quality factor Q can be obtained, and the temperature stability of the resonance frequency can be improved. ±
It turns out that it has the outstanding characteristic within 0.05%. still.
The Curie temperature was 280 ° C or higher. Example 3 Sample no. 4, that is, the composition formula (Pb _0.985 R
_0.015 ) [(Nb _0.58 Mn _0.17 Fe _0.25 ) _0.1 Mn
After weighing the raw material powder represented by _0.01 (Ti _0.506 Zr _0.494 ) _0.89 ] O ₃ , the raw material powder was weighed using a _{5 mmφ} ZrO ₂ ball.
After wet mixing, discharging, drying and sizing, the mixture is put into an Al ₂ O ₃ crucible and calcined at a temperature of 950 ° C. for 3 hours. ,
D90 has a particle size distribution of 1.3 μm and a specific surface area of 2.0 c
A ground powder having a m ² / g was obtained.

[0069] A binder and a plasticizer are added to the obtained pulverized product and dispersed in an organic solvent to prepare a slurry. Using the obtained slurry, a thickness of 1
An 80 μm ceramic green sheet was produced. An Ag-Pd paste is screen-printed on one side of the green sheet. The printed green sheets are laminated, and the green sheets are pressed and integrated by a hot press, and
After degreasing by heating at 0 ° C., the laminate was fired at a temperature of 1120 ° C. for 3 hours to obtain a laminated ceramic.

An electrode paste containing silver and glass as main components is applied to both main surfaces of the obtained laminated ceramic to form a first voltage input portion, a voltage output portion, and a second voltage input portion, and the electrodes are baked. After that, external electrodes were formed on the side surfaces of the laminated portion by connection with electrodes inside the porcelain using a conductive paste.

Next, a DC electric field of 1.1 kV / mm was applied to the voltage input electrode and the voltage output electrode formed on both main surfaces of the laminate in silicon oil at 200 ° C. for 30 minutes, respectively, and polarization treatment was performed. Thus, the multilayer piezoelectric transformer shown in FIG. 2 was obtained.

The dimensions of the obtained laminate were L × W × T = 4
It was 0.5 mm × 33.5 mm × 2.8 mm. The distance between the power input unit and the power output unit was 1.2 mm.

Next, a DC electric field of 1.1 kV / mm was applied to the voltage input electrode and the voltage output electrode formed on both main surfaces of the laminate in silicon oil at 200 ° C. for 30 minutes.
Polarization was performed by applying the voltage to obtain a laminated piezoelectric transformer.

As shown in FIG. 3, the measuring circuit includes a first voltage input section A, a second voltage input section C, and a voltage output section B of the piezoelectric transformer.
0Ω was connected. A voltage obtained by adding an offset voltage of 70.7 V to a sine wave having an amplitude of 70.7 V as an input voltage was applied from a DC power supply to input electrodes of the first voltage input section A and the second voltage input section C via an amplifier. At this time, the current I _in and the voltage V _in applied to the input-side electrode, and the voltage V _out and the current I _out output from the output-side electrode of the voltage output unit B were measured.
The output power P _out and the conversion efficiency η were calculated from the following equations.

P _out = V _out × I _out (unit: W) η = (V _out × I _out ) ÷ (V _in × I _in ) × 100 (unit:%) As a result, the output power is reduced at the driving frequency of 130 kHz. 30 W, efficiency was 94%.

[0076]

According to the piezoelectric ceramic composition of the present invention, the temperature stability of the resonance frequency can be improved by replacing the A site of the perovskite-type composite oxide with Gd, Sm, and Nd. The B site of the system is tetravalent, but by substituting a predetermined amount with divalent to tetravalent Mn,
Curie temperature Tc can be suppressed from lowering, and the mechanical quality factor Q
m can be suppressed, whereby the electromechanical coupling coefficient K
The temperature stability of the resonance frequency can be improved while maintaining p and the mechanical quality factor Qm high.

By using such a piezoelectric ceramic composition as a piezoelectric substrate of a piezoelectric transformer, a piezoelectric transformer having an output of 20 W or more and an efficiency of 85% or more can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a single-plate type piezoelectric transformer of the present invention.

FIG. 2 is a perspective view showing a multilayer piezoelectric transformer of the present invention.

FIG. 3 is a diagram showing a measurement circuit of the piezoelectric transformer of the present invention.

[Explanation of symbols]

11, 21,... Piezoelectric substrate 12, 13, 15, 16, 22a-d, 23a-d,.
-Input-side electrodes 14, 17, 24a to j-Output-side electrodes A1, A2-First voltage input section B1, B2-Voltage output sections C1, C2-Second voltage input section

Claims (2)

[Claims] 1. Pb, Zr, Ti, Nb,
A perovskite-type composite oxide containing Mn and Fe and at least one of Gd, Sm, and Nd,
The composition formula by molar ratio of the metal elements _{(Pb (1-a) x} R a) _{[(Nb 1-ef Mn e Fe} f) b Mn
_{c (Ti d Zr 1-d} ) 1-b - c ] O ₃ (where, R represents Gd, Sm
And at least one of Nd), a, b, c, d and x are 0.005 ≦ a ≦ 0.025 0.07 ≦ b ≦ 0.140 <c ≦ 0.020. A piezoelectric ceramic composition characterized by satisfying 50 <d ≦ 0.55 0.98 ≦ x ≦ 1.02. 2. A voltage input portion and a voltage output portion are alternately formed in a longitudinal direction of a piezoelectric substrate having both main surfaces of a rectangular shape having a length L and a width W, and the voltage input portion and the voltage output portion are respectively formed. A piezoelectric transformer comprising an input electrode and an output electrode, wherein a piezoelectric layer of the piezoelectric substrate is made of the piezoelectric ceramic composition according to claim 1.