JPH03122050A - Piezoelectric material - Google Patents

Abstract

PURPOSE:To improve electromechanical coupling coefficient in radial direction, dielectric constant and piezoelectric constant by substituting a part of Pb with Sr and/or Ca. CONSTITUTION:A mixture is produced by mixing PbO, ZrO2, TiO2, MgO, Nb2O5, NiO and Ta2O5 at ratios to satisfy the formula (10<=a+b<=55; 30<=c<=50; 2.5<=d<=60; 0.01<=b/a<=2.0; a+b+c+d=100; a, b, c and d are mol%). The mixture is incorporated with 1-10 atom% of one or more kinds of metals selected from Sr and Ca, calcined at 900-1,100 deg.C and crushed. The calcination product is crushed, mixed, incorporated with an organic binder, formed and baked at 1,200-1,300 deg.C.

Description

[Detailed Description of the Invention] (Field of Industrial Application) This invention has a large radial electromechanical coupling coefficient, relative dielectric constant, and piezoelectric constant, and is useful as a material for piezoelectric actuators, piezoelectric buzzers, etc. that utilize piezoelectric strain. Concerning suitable piezoelectric materials.

(Prior art) As piezoelectric materials, lead zirconate titanate, Pb(
Zr,Ti)Os porcelain compositions are well known. This compound has advantages such as having high piezoelectricity, being usable up to high temperatures, and furthermore, by substituting or adding a third component, porcelain that is highly modified can be obtained. In particular, Pb (where some of Zr and Ti are replaced with Mg and Nb)
Mg+7sNbzzt)O+ PbTiOs Pb
ZrOs three-component piezoelectric ceramics are easy to fire with little evaporation of Pbo, and can have various piezoelectric properties by adding various additives to the main component, so piezoelectric buzzers and frequency It has been used as a material for filters, piezoelectric ignition elements, etc. In addition, Pb(Ni1
/3Ta2/3)O3 PbTiOs PbZrO
The three-component material s has high piezoelectricity and stability, and is suitable as a material for ultrasonic vibrators, Lylter, etc.

In recent years, the need for precise displacement elements has increased in the fields of precision machinery, optical instruments, etc., and attempts have been made to use displacement driving elements that utilize piezoelectric distortion.

Piezoelectric materials used in such fields are required to have a large radial electromechanical coupling coefficient, relative permittivity, and piezoelectric constant.

Among the conventionally known materials, for example, Japanese Patent Publication No. 42971
Pb(Mg+7Jbzz3O
Although zPbTiOi PbZrO3 has a large radial electromechanical coupling coefficient of 50 to 70%,
The dielectric constant is about 2500 at most. As a material with a high relative dielectric constant, a part of the Pb having the above composition disclosed in Japanese Patent Publication No. 17103/1983 can be replaced with Sr, Ba,
There are materials substituted with Ca, but the piezoelectric constant of this type of material is 300 to 315 (X 10-'''m/V)
Pb(Ni+zzTatys)OzP disclosed in Japanese Patent Publication No. 46-28467
bTiO3PbZr0z has a maximum dielectric constant of about 360
0, but conversely, the radial electromechanical coupling coefficient is 40 to 6.
5%, and the piezoelectric constant is at most 250 (XIO-”m
/V).

(Problems to be Solved by the Invention) In response to the recent demand for higher performance of piezoelectric materials, the piezoelectric materials known so far as described above do not have sufficient characteristics. That is, either the dielectric constant or the electromechanical coupling coefficient is small, and the piezoelectric constant cannot be said to be sufficiently large. Therefore, when these materials are used as a piezoelectric actuator, there are disadvantages in that the amount of displacement is small and the driving voltage is large.

An object of the present invention is to provide a piezoelectric material that has a large relative dielectric constant, a radial electromechanical coupling coefficient, and a piezoelectric constant, and can obtain a large piezoelectric strain.

(Means for Solving the Problems) The present inventor has discovered that Pb, which has been recognized to have good properties,
(Mg+7Jbzz3Oz PbTiO3PbZr0
:+ and Pb(NiyzTa27x)Os PbTi0
1 PbZr0) composite, i.e. Pb(Mg+
zzNbzzi)O:+Pb(Ni+7iTazz
A detailed study of the four-component system of s) Oz PbTio and -PbZroz revealed that by appropriately selecting the ratio of the four components and replacing a portion of Pb with at least one of Sr, Ba and Ca, It was confirmed that a material with an extremely high piezoelectric constant could be obtained by simultaneously improving the dielectric constant and electromechanical coupling coefficient.

The gist of the present invention based on the above knowledge lies in the following piezoelectric material.

a Pb(Mg+7Jbzz3)Os b Pb(N
i+zzTat/5) Oz-c PbTiOs d
PbZr0=, the above a, b, c and d satisfy the following formulas (1) to (4), and 1 to 10 atomic % of Pb is one or more of Sr, Ba and Ca. Piezoelectric material that has been tA.

10<a+b≦55...■ 30≦c≦50...■ 2.5≦d≦60...■ 0.01≦b / a≦2.0... ■However, a,
, b, c,, d are mol%, a+b+c + d = 1
It is 00.

(Function) The ratio of each component constituting the piezoelectric material of the present invention, that is, the above-mentioned mol%, a, b, c, and d, was selected to satisfy the formulas from ■ to ■ within this range. This is because either the radial electromechanical coupling coefficient or the relative dielectric constant decreases outside, and the piezoelectric constant decreases, or the crystal structure changes and no piezoelectricity is exhibited at all.

In addition, the reason why the amount of substitution of Pb atoms with one or more of Sr, Ba, and Ca is set to 1 to 10 atomic % is because if any element is less than 1 atomic %, the dielectric constant will not improve much, and the piezoelectric constant will decrease. This is because no improvement is observed, and on the contrary, if the content exceeds 10 atomic %, the radial electromechanical coupling coefficient decreases significantly and the piezoelectric constant decreases.

The piezoelectric material of the present invention has the above-mentioned composition (1), and the manufacturing method thereof is the same as that of the conventional Yu-23 composition of this type. That is, it can be manufactured by mixing oxides, carbonates, hydroxides, etc. of each element so as to have the above-mentioned composition, molding, and then sintering.

(Example) A four-component basic composition is a Pb(Mg+7Jbzz3)Os b Pb(N
i+7iTazzs) Ozc PbTiO3-d Pb
Zr0i ((tanshi, a + b + c + d = 100), PbO, Zr0z+riot, MgO, NbzQ
s, Nip, Tag's, 5rCO=, BaC
One or more of O5 and CaC01 was added as appropriate and weighed to give the composition shown in Table 1, and thoroughly mixed using a ball mill. The obtained mixed powder was heated at 900 to 1100°C for about 2
After calcining for a time, the calcined product was thoroughly ground and mixed again in a ball mill, and then an organic binder was mixed therein and granulated. This granulated powder is heated to a diameter of 20 cm at a pressure of about 1'/c+a.
Molded to a thickness of 2m111 and heated at 1200 to 1300°
The mixture was fired at a temperature of C for about 2 hours.

Silver electrodes were baked on both sides of the obtained disc-shaped sintered body, and 40~
Polarization treatment was performed by applying a dino fence DC voltage to 2 and 3 in silicone oil at 100°C.

Table 1 shows the composition of the porcelain obtained above and its electrical properties. Note that C7°/ε in the table. is relative dielectric constant, Kr is radial electric m, vi coupling coefficient, d! + is the transverse piezoelectric constant.

In the samples Nα1 to Nα26 in Table 1, a, b, c, d
The value of is changed. If you look at the comparative example in the notes column, the values of a, b, c, and d are the same as (1) to (
It can be seen that d3+ becomes small if the equation 4) is not satisfied.

Samples 27 to 48 are samples in which the values of a, b, c, and d are set to constant values within the range defined by the present invention, and the amounts of Pb replaced by Sr, Ha, and Ca are varied.

However, Nα27 is a comparative example in which no substitution was made.

Looking at these electrical properties, it can be seen that there is no effect of increasing the dielectric constant when the substitution element is less than 1 atomic %, regardless of whether the substitution element is S, Ba, or Ca, while on the other hand, when the substitution exceeds 10 atomic %, It can be seen that d,1 deteriorates extremely.

From the above results, all the equations from ■ to ■ above are satisfied, and P
It can be seen that when part of b is replaced with an appropriate amount of at least one of Sr, Ba, and Ca, a material exhibiting a high electromechanical coupling coefficient, a high dielectric constant, and a large piezoelectric constant can be obtained.

(Hereinafter, blank spaces) (Effects of the Invention) As shown in the examples, the piezoelectric material of the present invention has excellent characteristics in all of the radial electromechanical coupling coefficient, dielectric constant, and piezoelectric constant. The various uses mentioned make it extremely useful as a material.

Claims (1)

[Claims] aPb(Mg_1_/_3Nb_2_/_3)O_3-
bPb(Ni_1_/_3Ta_2_/_3)O_3-
It is represented by cPbTiO_3-dPbZrO_3, the above a, b, c and d satisfy the following formulas (1) to (4), and 1 to 10 atomic % of Pb is one or more of Sr, Ba and Ca. Piezoelectric materials being replaced. 10<a+b≦55 (1) 30≦c≦50 (2) 2.5≦d≦60 (3) 0.01≦b/a≦2 .0...(4) However, a
, b, c, and d are mol%, and a+b+c+d=100.