JPH0517214A - Piezoelectric porcelain material - Google Patents

Abstract

PURPOSE:To obtain a PbTiO3-based piezoelectric porcelain material having improved thermal aging characteristics, resonance frequency stabilized to thermal shock, improved sinterability, improved dense structure and satisfactory polarizability. CONSTITUTION:yPb(Mg1/2W1/2)O3-(1-y)[Pb(1-1.5x-z)(La1-aNda)x]TiO3 (where x=0.02-0.20, y=0.01-0.06, -0.10<=z<=0.10 and 0<=a<=1) is prepd. as a base, at least one among 1-12mol% each of Ca, Sr and B is substd. for part of Pb in the [Pb(1-1.5x-z)(La1-aNda)x]TiO3 and 0.1-2.0wt.% (expressed in terms of MnO2) Mn is incorporated to obtain a piezoelectric porcelain material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric ceramic material which has a large electromechanical coupling coefficient in the thickness direction and a large piezoelectric constant and is suitable as a material for a piezoelectric actuator, an oscillator, a resonator, a filter or the like utilizing piezoelectric strain.

[0002]

2. Description of the Related Art Piezoelectric ceramic materials are used as piezoelectric materials by taking advantage of the fact that distortion occurs when an electric field is applied. For example, piezoelectric vibrators, resonators, oscillators, ceramic filters, surface acoustic wave filters. It is used for pyroelectric elements. This piezoelectric ceramic material includes a porcelain containing PbTiO ₃ as a main component, or a porcelain containing Pb (Ti, Zr) O ₃ as a main component,
Furthermore, Pb (M
Various materials for porcelain in which n _1/3 Nb _2/3 ) O ₃ , Pb (Ni _1/3 Nb _2/3 ) O _{3 and the} like are solid-solved are known.

Of these, the PbTiO ₃ -based porcelain material has been variously studied for materials in which the Pb position is modified, and has a large electromechanical coupling coefficient in which the vibration in the thickness direction is larger than the vibration in the spreading direction, and the dielectric constant is Piezoelectric porcelain, which is characterized by being small, has been found. This PbTiO ₃ -based compound has advantages that it has a large piezoelectric property and that a modified piezoelectric ceramic can be obtained by substituting or adding the third component.

[0004] The present inventors have, for such PbTiO ₃ based ceramic material extensive _{research, Pb (Mg 1/3 Nb 2/} 3) O 3, Pb (Ni 1/3 Sb
_2/3 ) O ₃ , PbTiO ₃ , and PbZrO ₃ with different composition ratios,
We have developed a piezoelectric porcelain with improved radial electromechanical coupling coefficient, relative permittivity and piezoelectric constant. (See Japanese Laid-Open Patent Publication No. 3-50156) In recent fields of precision machinery, optical machinery, etc., the need for precision displacement elements has increased, and attempts have been made to use displacement drive elements utilizing piezoelectric strain. .. As piezoelectric ceramic materials used in such fields, in addition to large radial electromechanical coupling coefficient, relative dielectric constant and piezoelectric constant, thermal aging characteristics (rate of change of piezoelectric ceramic material over time)
Is required to be excellent.

[0005]

However, it is hard to say that existing piezoelectric ceramic materials have sufficient characteristics in response to the recent demand for higher performance of piezoelectric materials. That is, the PbTiO ₃ system porcelain as described above has the drawbacks of being inferior in thermal aging characteristics and being unstable with respect to a rapid temperature change in the surroundings (hereinafter referred to as “thermal shock”). Due to the poor thermal aging characteristics, if the piezoelectric ceramic is left at a high temperature, the piezoelectric characteristics and electrical characteristics will deteriorate over time. Also, when subjected to thermal shock, the resonance frequency becomes unstable. Further, the PbTiO ₃ -based porcelain containing an oxide additive such as Nd ₂ O ₃ or MnO ₂ has a problem that it is difficult to sinter, a dense structure cannot be obtained, and therefore polarization is difficult.

According to the present invention, in a PbTiO ₃ -based piezoelectric ceramic material, the thermal aging characteristics are improved, the resonance frequency is stabilized against the thermal shock, and the sinterability and the dense structural property are further improved. It aims to improve polarity, improve quality stability and mechanical quality.

[0007]

The gist of the present invention lies in the following piezoelectric ceramic materials.

_Y Pb (Mg _1/2 W _1/2 ) O ₃ − _(1-y) [Pb
_{(1-1.5X -Z)} (La _1-a Nd _a ) _X ] TiO ₃ as the main component, and (P
b _{(1-1.5X -Z)} (La _1-a Nd _a ) _X ] is partially substituted with Pb by 1 to 12 mol% of at least one of Ca, Sr, and Ba, and Mn converted to MnO ₂ 0.1
~ 2.0% by weight and x, y, z are as follows:
A piezoelectric ceramic material characterized by satisfying the equations, and.

However, x = 0.02 to 0.20 y = 0.01 to 0.06 -0.10≤z≤0.10 0≤a≤1

[0010]

The function of each component in the composition of the present invention will be described below.

The inclusion of Pb (Mg _1/2 W _1/2 ) O ₃ reduces the change in resonance frequency even when subjected to thermal shock. Pb
_{(1-1.5X -Z)} (La _1-a Nd _a ) _X part of Pb is Ca, Sr, Ba
When it is replaced with at least one of the metal oxides, the absolute value of the thermal aging characteristics becomes small. Lead titanate (Pb _{(1-1.5X -Z)} (La _1-a Nd _a ) _X ) TiO ₃
If Pb is partially replaced by La or Nd and MnO ₂ is contained in the above component, there is an advantage that it is easily sintered and has a dense structure and is easily polarized.

Further, the above-mentioned piezoelectric ceramic material is (La _1-a N
d _a ) _X amount (hereinafter referred to as “x amount”), Pb (Mg _1/2 W
The amount of _1/2 ) O ₃ (hereinafter referred to as “y amount”), the amount of MnO _{2 and} the amount of at least one metal oxide of Ca, Sr, and Ba have the following upper and lower limits. If they exceed the limits, the properties of the piezoelectric ceramic material are affected.

That is, when the amount of x is in the range of 0.02 to 0.20, the sinterability of the porcelain becomes good, and when it is less than 0.02, grain growth remarkably occurs and a dense piezoelectric ceramic cannot be obtained. Deteriorates.

When the amount of y is less than 0.01, the rate of change of the resonance frequency is large when a thermal shock is applied, and when it exceeds 0.06, the electromechanical coupling coefficient k _{p of the} vibration in the spreading direction is large.
Therefore, this k _p and the electromechanical coupling coefficient k _{t of the} vibration in the thickness direction are
The value of k _t / k _p , which is the ratio of, decreases, and the piezoelectric characteristics deteriorate.

If the amount of MnO ₂ is less than 0.1% by weight, the effect of improving the sinterability of the piezoelectric ceramic cannot be obtained, and if it exceeds 2.0% by weight, the specific resistance of the piezoelectric ceramic becomes small and polarization becomes difficult.

If the amount of at least one metal oxide of Ca, Sr, and Ba is less than 1 mol%, the absolute value of the thermal aging property becomes large, and if it exceeds 12 mol%, the Curie point is lowered and the piezoelectric property is also increased. to degrade.

Substitution of Pb position by La and Nd is effective even if only one of La and Nd is effective.

Since Pb is quantitatively flexible, (La
_1-a Nd _a ) _X after being corrected considering the valence,
It can be increased or decreased within the range of ± 10 mol%. If the amount of increase / decrease of Pb exceeds +10 mol%, grain growth will occur remarkably, so that a dense piezoelectric ceramic cannot be obtained, and if it is less than −10 mol%, piezoelectricity will be significantly deteriorated. That is, z in the above equation is −
It may be 0.10 ≦ z ≦ 0.10.

In manufacturing the piezoelectric ceramic material of the present invention,
As a raw material, PbO (or Pb ₃ O ₄ ), TiO ₂ , La ₂ O ₃ , Nd ₂ O
₃ , MnO ₂ oxides or CaCO ₃ , SrCO ₃ , BaCO
_3, MgCO _3, WCO _3, it is possible to use each of the carbonates of MnCO _3. The composition of the final piezoelectric ceramic material is _y Pb
(Mg _1/2 W _1/2 ) O _{3- (1-y)} [Pb _{(1-1.5X -Z)} (La _1-a Nd _a )
_X ] TiO ₃ formula is weighed and blended so as to satisfy the above formulas and wet-mixed in a pot mill. Then, it is dehydrated and dried, and calcined at 800 to 1100 ° C for 1 to 3 hours, and the calcined powder is further pulverized by a pot mill or the like. After that, an organic binder is added, pressure molding is performed at a pressure of about 0.5 to 2.0 t / cm ² , and firing is performed at a temperature of about 1200 to 1300 ° C. for 2 hours to obtain a piezoelectric ceramic. After polishing the piezoelectric ceramic material obtained in this way, electrodes were formed on both sides by silver deposition, 1
A predetermined piezoelectric ceramic material can be obtained by performing polarization treatment at 50 ° C. for 2 to 6 KV / mm for 10 to 20 minutes.

The piezoelectric ceramic material of the present invention obtained by the above manufacturing method has a small absolute value of thermal aging characteristics,
It has excellent thermal aging characteristics such as piezoelectric characteristics and electrical characteristics.
In addition, the resonance frequency is stable even when subjected to thermal shock. Furthermore, the sinterability, dense structure, and polarizability have been improved, making it an excellent piezoelectric ceramic material. When this piezoelectric ceramic material is used for pyroelectric elements, resonators, oscillators, filters, etc.,
A product with excellent properties can be obtained. In particular, when it is used as a reference signal of a digital IC or a vibrator used in a transmission circuit, excellent effects are exhibited.

[0021]

[Example] As raw materials, PbO (or Pb ₃ O ₄ ), TiO ₂ , La
₂ O ₃ , Nd ₂ O ₃ , CaCO ₃ , SrCO ₃ , BaCO ₃ , MgCO ₃ , WCO
₃ , MnO ₂ special grade reagent was used.

The piezoelectric material having the composition of the present invention and the composition of the comparative example were weighed and wet mixed in a pot mill. After this wet mixing, it was dehydrated and dried, and calcined at 800 to 1100 ° C for 2 hours. Next, this calcined powder was further pulverized by a pot mill. After that, add an organic binder and add 0.5-
A disk having a diameter of 20 mm and a thickness of 1.5 mm was pressure-molded at a pressure of about 2.0 t / cm ^{2 and then} fired at a temperature of about 1200 to 1300 ° C. for 2 hours. The piezoelectric ceramic material thus obtained was polished to a thickness of 0.5 mm, and then electrodes were formed on both sides by silver vapor deposition.
The piezoelectric property and the electrical property of each were measured by polarization for 10 minutes at 2 ° C to 6 KV / mm. The measurement item, the electromechanical coupling coefficient in the thickness direction vibration (k _t), a thermal aging characteristics of thermal shock after the change rate and the k _t of the resonance frequency in the thickness direction vibration (fr). The condition of thermal shock is 30 at -40 ℃.
After leaving it for 1 minute, it was allowed to stand at 80 ° C. for 30 minutes, and this was regarded as one cycle, and 100 cycles were performed.

Further, heat aging characteristics, 300 ° C., shows the rate of change of the electromechanical coupling coefficient of the heat-treated before and after the thickness direction vibration under the conditions of 1 hour (k _t). It should be noted that those marked with * in Table 1 are outside the scope of the present invention, and all other items are within the scope of the present invention.

Table 1 shows the results.

[0025]

[Table 1 (1)]

[0026]

[Table 1 (2)]

Looking at the comparative example in Table 1, y amount = 0,
That is, No. 4 containing no Pb (Mg _1/2 W _1/2 ) O ₃
Has a low sintering density and a large amount of change in resonance frequency after thermal shock.

No. 5, which has an excessive y amount, has a large amount of change in resonance frequency after thermal shock. No. 9 in which Ca, Sr, and Ba were not replaced with metal oxides also had a large change in resonance frequency due to thermal shock. In addition, the amount of substitution with these metal oxides is large.
No. 22 has low piezoelectricity and poor thermal aging characteristics. Mn
No. 13, which has a large amount of O _2, is difficult to polarize, and No. 12, which does not contain MnO ₂ , has poor resonance frequency change rate and thermal aging characteristics. x amount = 0, that is, No. 19 containing no La or Nd had difficulty in sintering due to abnormal grain growth, and No. 15 with a large amount of PbO was also the same. No. 21, which has a large amount of x, has low piezoelectricity and poor thermal aging characteristics. In addition, No. 18 with a small amount of PbO has small piezoelectricity and poor thermal aging characteristics. On the other hand, those having the composition within the range of the present invention exhibited good piezoelectric and electrical characteristics.

[0029]

EFFECTS OF THE INVENTION The piezoelectric ceramic material of the present invention has a small absolute value of thermal aging characteristics, improves the thermal aging characteristics such as piezoelectric characteristics and electrical characteristics, and stabilizes the resonance frequency even when it is subjected to thermal shock. It is an excellent piezoelectric ceramic material with improved binding properties, dense structure and polarizability.

Claims (1)

Claims 1. _y Pb (Mg _1/2 W _1/2 ) O _{3- (1-y)} [Pb
_{(1-1.5X -Z)} (La _1-a Nd _a ) _X ] TiO ₃ as the main component, and (P
b _{(1-1.5X -Z)} (La _1-a Nd _a ) _X ] is partially substituted with Pb by 1 to 12 mol% of at least one of Ca, Sr, and Ba, and Mn converted to MnO ₂ 0.1
~ 2.0% by weight and x, y, z are as follows:
A piezoelectric ceramic material characterized by satisfying the equations, and. However, x = 0.02 to 0.20 y = 0.01 to 0.06 −0.10 ≦ z ≦ 0.10 0 ≦ a ≦ 1