JP3239778B2 - Piezoelectric ceramic composition - Google Patents

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 more particularly to a piezoelectric ceramic composition useful as a material for a piezoelectric ceramic sensor or the like.

[0002]

2. Description of the Related Art As a piezoelectric ceramic composition used for a piezoelectric ceramic element such as a piezoelectric ceramic sensor, a lead zirconate titanate (PbZr _x Ti _1-x O ₃ ) has been conventionally used.
Piezoelectric ceramic compositions containing as a main component have been widely used.

[0003]

However, the piezoelectric ceramic composition containing lead zirconate titanate as a main component usually has a Curie temperature of 200 to 400 ° C., and in a temperature range exceeding the Curie temperature, the piezoelectric material has a piezoelectricity. However, there is a problem that the properties of the piezoelectric ceramic sensor are lost and the piezoelectric ceramic element such as a piezoelectric ceramic sensor cannot be used.

On the other hand, as a piezoelectric ceramic composition having a Curie temperature exceeding 400 ° C., lead niobate (PbNb ₂ O ₆ ) having a Curie temperature of about 570 ° C. has been known.

However, the piezoelectric ceramic composition containing lead niobate as a main component generally has poor sinterability, for example, PbN
In the case of b ₂ O ₆ , it was difficult to obtain a polarized sintered body by firing at atmospheric pressure. For sintering, a special firing method such as a hot press method had to be adopted.

In connection with this problem, a part of Pb is replaced with Ca,
It has been known that sinterability is improved by substituting with Ba or the like, and a good sintered body can be obtained by firing at atmospheric pressure.
However, when a part of Pb is replaced with Ca, Ba, or the like, there is a problem that the Curie temperature is remarkably lowered. For example, when a part of Pb is replaced with Ca, about 30 mol% of Pb is replaced with Ca and calcined at atmospheric pressure to obtain a polarizable sintered body, but the obtained piezoelectric sintered body is obtained. Curie temperature dropped to 400 ° C. or lower.

Therefore, an object of the present invention is to sinter under atmospheric pressure, wherein the Curie temperature exceeds 400 ° C.
An object of the present invention is to provide a piezoelectric ceramic composition useful as a piezoelectric ceramic element used at a high temperature such as a piezoelectric ceramic sensor.

[0008]

Means for Solving the Problems To achieve the above object, the piezoelectric ceramic composition of the present invention comprises ( Pb _{1- (a + b + c)} L
_{i 2a A b La 2C / 3} ) x Nb y O 3y- δ ( where, A is Ca, Sr, at least one of Ba
Yes, δ represents the amount of O defects ) 0 ≦ a, 0 ≦ b, 0 <c 0.015 ≦ a + b + c ≦ 0.225 0 <x, 0 <y x / y <1/2 Tungsten bronze type Characterized by having a porcelain composition having the above crystal structure as a main component.

[0009] The piezoelectric ceramic composition of the present invention have the general formula _{(Pb 1- (a + b +} c) Li 2a A b La 2c / 3) x (Nb
_{1- (d + e + f +} g) Sb 5d / 3 Zr 5e / 4 Ta f W 5g / 6) y O 3y- δ ( where, A is Ca, Sr, at least one of Ba
And δ represents the defect amount of O ) 0 ≦ a, 0 ≦ b, 0 <c , 0 ≦ d, 0 ≦ e, 0 ≦ f, 0
≦ g, 0.015 ≦ a + b + c ≦ 0.225 0 <d + e + f + g ≦ 0.2 0 <x, 0 <y x / y <1/2 The main component is a porcelain composition having a tungsten bronze type crystal structure. It is characterized by doing.

Further, at least one of oxides of Mn, Cr, Ni and Co is converted into MnO ₂ , Cr ₂ O ₃ , NiO and Co ₂ O ₃ as subcomponents with respect to the main component. Then, it is preferable that the total content be 5.0% by weight or less.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the piezoelectric ceramic composition of the present invention will be described.

First, Pb ₃ O ₄ , Li ₂
CO ₃ , CaCO ₃ , SrCO ₃ , BaCO ₃ , La ₂ O
_{3, Nb 2 O 5, Ta} 2 O 5, Sb 2 O 3, ZrO 2, W
O ₃ , MnCO ₃ , Cr ₂ O ₃ , NiO and Co ₂ O ₃ were prepared.

Thereafter, these raw materials are represented by the general formula ( Pb
_{1- (a + b + c)} Li 2a A b La 2c / 3) x (Nb 1- (d + e + f + g) Sb
_{5d / 3 Zr 5e / 4 Ta} f W 5g / 6) y O 3y- δ ( where, A is C
a, Sr, or Ba, and δ is O
(Representing the amount of defects ), and weighed and collected so as to have a composition specifically as shown in Table 1. In addition, those without La added, La
Weighed and dispensed with Y as a comparative example
Was.

The raw material corresponding to Li in the general formula is Li
CO ₃ is the raw material corresponding to A is CaCO ₃ , SrCO ₃
And BaCO is _3, La falls raw material is La ₂ O _3, the raw material falls Sb is Sb ₂ O _3, the raw material falls Zr is ZrO _2, the raw material falls Ta is Ta ₂
O ₅ and the raw material equivalent to W is WO ₃ .

Next, a solvent such as water or isopropyl alcohol was added to the weighed and separated raw material mixture and wet-mixed for about 4 hours using a ball mill. Thereafter, the wet mixture was dried, calcined at 700 ° C to 900 ° C, and coarsely pulverized.

[0016]

[Table 1]

Next, an organic binder is added to the calcined and pulverized product, and the mixture is wet-mixed and pulverized for 4 hours using a ball mill.
The particle size was adjusted through a 40 mesh sieve. After that, it was compressed at a pressure of 1000 kg / cm ^{2 to} a
m, after molding into a 1.2 mm thick disc, 1250-1
It was fired in the air at a temperature of 300 ° C. to obtain a disc-shaped porcelain (porcelain disc).

Thereafter, a silver paste is applied to both main surfaces of the porcelain disc by applying and baking to form silver electrodes.
A polarization voltage was applied by applying a DC voltage of 5 to 10 kV / mm in an insulating oil at 00 ° C. for 10 to 30 minutes to obtain a piezoelectric ceramic disk (sample).

Next, the density (ρ), the Curie point (Tc), the electromechanical coupling coefficient (Kt) in the vibration in the thickness direction, and the piezoelectric constant (d ₃₃ ) of these samples were measured. Table 2 shows the results. In Tables 1 and 2, those marked with * are out of the scope of the present invention, and others are within the scope of the present invention. However, sample No. 13 is out of the scope of the invention at the level of claim 3 . Kt measures the resonance frequency and the anti-resonance frequency with an impedance measuring instrument,
It was determined by calculation. d ₃₃ was obtained by measuring the amount of charge generated by applying a stress and calculating the amount.

[0020]

[Table 2]

As is clear from Table 2, for each sample within the scope of the present invention, the density was 5.5 to 6.3 g / cm ^3.
And a sintered body which can be used as a piezoelectric ceramic element has been obtained. The Curie point of the obtained piezoelectric ceramic exceeds 400 ° C., and Kt and d ₃₃
It can be seen that both values are excellent.

On the other hand, the general formula ( Pb _{1- (a + b + c)} L
_{i 2a A b La 2c / 3} ) x (Nb 1- (d + e + f + g) Sb 5d / 3 Zr
_{5e / 4 Ta f W 5g /} 6) y O 3y- δ ( where, A is Ca, Sr,
Ba is at least one, and δ represents the amount of O defects.
In the case of (1 ), those outside the scope of the present invention have poor properties as described below, and a piezoelectric ceramic for a high temperature having a Curie temperature exceeding 400 ° C., which is the object of the present application, cannot be obtained.

[0023] In other _{words, (Pb 1- (a + b} + c) Li 2a A b L
a _{2c / 3} ) x and ( Nb _{1- (d + e + f + g)} Sb _{5d / 3} Zr _{5e / 4} T
a _f W _{5g / 6} ) When the relationship of the quantity y is x / y ≧ 1/2,
As shown in Sample No. 1, sintering was insufficient and the density of the porcelain was low, and the porcelain could not be polarized.

A + b + c is less than 0.015, that is, Pb
When the amount (1- (a + b + c)) exceeds 0.985, as shown in Sample No. 3, sintering is insufficient, the density of the porcelain is small, and the porcelain cannot be polarized. On the other hand, a
+ B + c exceeds 0.225, that is, the amount of Pb (1- (a
+ B + c)) is less than 0.775, sample number 7
The Curie temperature becomes 400 ° C. or lower as shown in FIG.

When d + e + f + g exceeds 0.2, that is, when the amount of Nb (1- (d + e + f + g)) is less than 0.8, the Curie temperature becomes 400 ° C. or lower as shown in Sample No. 25. .

Also, La is added as a Pb substitution element.
No. 17 to 21 are samples to which La was added.
In comparison with No. 5, the electromechanical coupling coefficient and the piezoelectric constant
No improvement can be expected.

_{Furthermore, (Pb 1- (a + b} + c) Li 2a A b La
_{2c / 3)} amount x and _{(Nb 1- (d + e +} f + g) Sb 5d / 3 Zr 5e / 4 Ta f
W _{5g / 6} ) when the relationship of the quantity y is x / y ≧ 1/2,
When the Pb amount (1- (a + b + c)) is less than 0.775, the Curie temperature is 400
° C or lower.

When the subcomponent is added in an amount exceeding 5.0% by weight, the density of the porcelain is insufficient due to insufficient sintering and the porcelain may be polarized as shown in Sample No. 13. Can not.

[0029]

As apparent from the above description, according to the present invention, a piezoelectric ceramic which is fired in the air, has a Curie temperature exceeding 400 ° C., and is used at a high temperature such as a piezoelectric ceramic sensor. A lead niobate-based piezoelectric ceramic composition useful as an element is obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-211566 (JP, A) JP-A-51-58700 (JP, A) ROLAND BRIOT, et al. "PROPERTIES OF S UBSTITUTED PbNb2O6 CERAMICS AND MEAS UREMENT OF THEIR L OW ELECTROMECHANIC AL COEFFICIENTS ", F erroelectrics (1992), No. 134, pp. 163-168 (58) investigated the field (Int.Cl. ^7, DB name) C04B 35/00-35/22 C04B 35/42-35/50 C04B 35/62-35/632 CA (STN) REGISTRY (STN)

Claims (3)

(57) [Claims] 1. A general formula _{(Pb 1- (a + b +} c) Li 2a A b La 2C / 3) x Nb y O
_3y- δ ( where A is at least one of Ca, Sr, and Ba
There, [delta] is expressed by representing the amount of defects O), with 0 ≦ a, 0 ≦ b, 0 <c 0.015 ≦ a + b + c ≦ 0.225 0 <x, 0 <y x / y <1/2 A piezoelectric ceramic composition comprising, as a main component, a ceramic composition having a certain tungsten bronze structure type crystal structure. . Wherein general formula _{(Pb 1- (a + b +} c) Li 2a A b La 2c / 3) x (Nb
_{1- (d + e + f +} g) Sb 5d / 3 Zr 5e / 4 Ta f W 5g / 6) y O 3y- δ ( where, A is Ca, Sr, at least one of Ba
And δ represents the amount of defects of O ) 0 ≦ a, 0 ≦ b, 0 <c, 0 ≦ d, 0 ≦ e, 0 ≦ f, 0
≦ g, 0.015 ≦ a + b + c ≦ 0.225 0 <d + e + f + g ≦ 0.2 0 <x, 0 <y x / y <1/2 The main component is a porcelain composition having a tungsten bronze type crystal structure. A piezoelectric ceramic composition comprising: 3. Mn, Cr, Ni and Co as subcomponents
At least one of the oxides of MnO ₂ , Cr ₂ O ₃ , N
iO and Co ₂ O ₃ , respectively, for a total of 5.0
The piezoelectric ceramic composition according to claim 1, wherein the content is not more than weight%.