Piezoelectric ceramic composition and piezoelectric device using the same

A piezoelectric ceramic composition comprises a composite oxide of Pb, Ti and Zr as a main component and Mn and at least one metal element selected from the group consisting of Y, Dy, Er, Ho, Tm, Lu and Yb as subsidiary components. A piezoelectric device comprises such a piezoelectric ceramic composition.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a piezoelectric ceramic composition for 
use in a ceramic filter, a ceramic oscillator, a piezoelectric transducer, 
a variety of ceramic sensors, a ceramic buzzer or the like. The present 
invention also relates to a piezoelectric device such as a piezoelectric 
ceramic oscillator and a piezoelectric ceramic filter including a 
capacitive part and a piezoelectric oscillating part using the 
piezoelectric ceramic composition. 
2. Description of the Prior Art 
Conventional examples of a piezoelectric ceramic material include so-called 
PT ceramics comprising PbTiO.sub.3 as a main component, so-called PZT 
ceramics comprising Pb(Ti, Zr)O.sub.3 as a main component, and a 
multi-component piezoelectric ceramic composition comprising several types 
of composite perovskite compositions such as Pb(Mg.sub.1/3 
Nb.sub.2/3)O.sub.3 and Pb(Ni.sub.1/3 Nb.sub.2/3)O.sub.3 in the form of a 
solid solution. The use of these compositions provides a wide range of 
piezoelectric ceramics varying in the characteristics by selecting a 
composition ratio of the components suitably to meet a purpose of use. For 
example, Pb(Zn.sub.1/3 Nb.sub.2/3).sub.A (Sn.sub.1/3 Nb.sub.2/3).sub.B 
Ti.sub.C Zr.sub.D O.sub.3 composition (disclosed in Japanese Patent 
Publication (Tokko-sho) Nos. 52-17239 and 51-7318) and Pb(Sn.sub.a 
Sb.sub.1-a).sub.X Ti.sub.Y Zr.sub.Z O.sub.3 composition (disclosed in 
Japanese Patent Publication (Tokko-sho) Nos. 54-32516 and 54-36757) are 
suitable for use in a high frequency ceramic oscillator or filter, because 
of their excellent piezoelectricity and small size of crystal grains. 
Therefore, these piezoelectric ceramic compositions are used in ceramic 
filters, ceramic oscillators, piezoelectric transducers, ceramic sensors 
or the like. 
However, there is a problem when such piezoelectric ceramics are heated to 
a temperature of about 250.degree. C. for, for example, solder reflow and 
cooled to room temperature. In this case, the piezoelectric properties 
such as resonance frequency of the piezoelectric ceramics before the heat 
treatment are different from those after the heat treatment. 
The heat treatment changes the piezoelectric properties including a 
mechanical quality factor (Q.sub.m), an electromechanical coupling 
coefficient (k.sub.t) and a dielectric constant 
(.epsilon./.epsilon..sub.0) of the conventional piezoelectric ceramic 
compositions. Thus, the conventional piezoelectric ceramic composition has 
poor heat resistance. In addition, the piezoelectric properties drift due 
to heat. This change due to thermal shock may lead to a change in the 
characteristics of the frequency dependence of a filter produced with such 
piezoelectric ceramics. Japanese Laid-Open Patent Publication (Tokkai-Hei) 
Nos. 8-239269 and 9-142930 disclose materials that are not affected by 
heat. More specifically, a composite oxide of Y, Nb or the like is allowed 
to be a component of the main component of PZT, or Cr is added thereto, so 
that the resistance of the piezoelectric ceramics becomes low. 
When an electronic component such as a ceramic filter and a ceramic 
oscillator is fabricated as a chip, a chip element is mounted with solder 
at a higher temperature. The temperature of the element may be about 
200.degree. C. When a piezoelectric device formed of a conventional 
piezoelectric ceramic composition is heated at 150.degree. C. for 1 hour, 
the resonance frequency fr changes by several % immediately after the heat 
treatment, when compared to that before the heat treatment. After the heat 
treatment, the resonance frequency fr changes over time and drifts to a 
value different from that before the heat treatment. In other words, the 
characteristics of the conventional piezoelectric ceramic composition 
change because of poor heat resistance, and drift occurs due to heat. 
Therefore, the piezoelectric device has low reliability and disadvantages 
in mass production. 
SUMMARY OF THE INVENTION 
Therefore, with the foregoing in mind, it is an object of the present 
invention to provide a PZT piezoelectric ceramic material having improved 
mass productivity and stability in quality by raising heat resistance 
against a heat treatment at about 250.degree. C. for a short period and 
improving thermal drift characteristics, and to provide a piezoelectric 
ceramic composition and a piezoelectric device using the piezoelectric 
ceramic composition having excellent heat resistance so that the 
piezoelectric properties change in only a small amount when the 
piezoelectric ceramic composition is heated at about 250.degree. C. for a 
short period and then cooled to room temperature. In particular, another 
object of the present invention is to provide a piezoelectric device using 
a piezoelectric ceramic composition that has a strictly controlled 
composition ratio so that the change in the resonance frequency is small, 
and the change in the capacitance is significantly small. 
A piezoelectric ceramic composition of the present invention comprises a 
composite oxide including Pb, Ti and Zr as a main component and Mn and at 
least one metal element selected from the group consisting of Y, Dy, Er, 
Ho, Tm, Lu and Yb as subsidiary components. 
According to another aspect of the present invention, a piezoelectric 
ceramic composition comprises a composite oxide represented by Formula (I) 
as a main component: 
EQU (1-x)Pb(M.sub.1/3 Nb.sub.2/3).sub.a Zr.sub.b Ti.sub.c O.sub.3 --xRMn.sub.d 
O.sub.1+2d (I) 
where 0&lt;x.ltoreq.0.1, 0.ltoreq.a.ltoreq.0.1, 0.ltoreq.b.ltoreq.0.7, 
0.3.ltoreq.c.ltoreq.1.0, a+b+c=1, 0.5.ltoreq.d.ltoreq.3, M is at least one 
metal element selected from the group consisting of Zn, Ni and Mg, and R 
is at least one metal element selected from the group consisting of Y, Dy, 
Er, Ho, Tm, Lu and Yb. 
According to another aspect of the present invention, a piezoelectric 
ceramic composition comprises a composite oxide including Pb and Ti as a 
main component, with a metal element R (where R is at least one metal 
element selected from the group consisting of Y, Dy, Er, Ho, Tm, Lu and 
Yb) and Mn also being present in the composition. The metal element R and 
Mn are contained in an amount so that an amount of an oxide of RMnO.sub.3 
is 1 to 10 mol % with respect to a total amount of the oxide and the 
composite oxide. 
When the metal element R and Mn are added to the composite oxide exhibiting 
piezoelectricity, the changes of the piezoelectric properties of the 
piezoelectric ceramic composition due to heat treatment can be reduced. In 
particular, changes over time in the piezoelectric properties can be made 
small. When the metal element R and Mn are contained in an amount less 
than 1 mol %, the effect of the addition of the metal element R and Mn is 
not sufficient. On the other hand, when the metal elements R and Mn are 
contained in an amount more than 10 mol %, the piezoelectric properties of 
the composition may not be sufficient. 
According to another aspect of the present invention, a piezoelectric 
ceramic composition comprises a composite oxide represented by Formula 
(II) as a main component: 
EQU (1-x)Pb(M.sub.1/3 Nb.sub.2/3).sub.a Zr.sub.b Ti.sub.c O.sub.3 
--xRMnO.sub.3(II) 
where 0.01.ltoreq.x.ltoreq.0.1, 0.ltoreq.a.ltoreq.0.1, 
0.ltoreq.b.ltoreq.0.7, 0.3.ltoreq.c.ltoreq.1.0, a+b+c=1, M is at least one 
metal element selected from the group consisting of Zn, Ni and Mg, and R 
is at least one metal element selected from the group consisting of Y, Dy, 
Er, Ho, Tm, Lu and Yb. 
According to another aspect of the present invention, a piezoelectric 
ceramic composition comprises a composite oxide represented by Formula 
(III) as a main component and a metal element R (where R is at least one 
metal element selected from the group consisting of Y, Dy, Er, Ho, Tm, Lu 
and Yb) and Mn as subsidiary components: 
EQU Pb(A, Nb).sub.x Zr.sub.y Ti.sub.1-x-y O.sub.3 (III), 
where 0.ltoreq.x.ltoreq.0.05, 0.35.ltoreq.y.ltoreq.0.80, and A is at least 
one metal element selected from the group consisting of Sn, Zn, Ni and Mg. 
The piezoelectric ceramic composition comprises the metal element R in an 
amount so that an amount of R.sub.2 O.sub.3 is 0.01 to 0.05 mol per mol of 
the main component. The piezoelectric ceramic composition comprises Mn in 
an amount so that the amount of Mn.sub.2 O.sub.3 is 0.01 to 0.05 mol per 
mol of the main component. 
According to another aspect of the present invention, a piezoelectric 
ceramic composition is a composition represented by Formula (IV): 
EQU Pb(Y.sub.(1-x)/2 Mn.sub.x/2 Nb.sub.1/2).sub.a (M.sub.1/3 Nb.sub.2/3).sub.b 
Zr.sub.c Ti.sub.d O.sub.3 (IV) 
where 0.ltoreq.x&lt;1.0, 0.01.ltoreq.a.ltoreq.0.15, 0.ltoreq.b&lt;0.2, 
0.ltoreq.c.ltoreq.0.68, 0.3.ltoreq.d.ltoreq.0.93, a+b+c+d=1, and M is at 
least one metal element selected from the group consisting of Zn, Ni and 
Mg. 
In one embodiment of the piezoelectric ceramic composition of the present 
invention, preferably, the piezoelectric ceramic composition further 
comprises at least one metal element selected from the group consisting of 
Fe, Cr, Co, Cu and Sn in an amount so that the amount of each of Fe.sub.2 
O.sub.3, Cr.sub.2 O.sub.3, CoO, CuO and SnO.sub.2 is 0.01 to 1.3wt %. 
According to another aspect of the present invention, a method for 
producing a piezoelectric ceramic composition comprises the steps of 
adding a subsidiary component RMnO.sub.3 (where R is at least one metal 
element selected from the group consisting of Y, Dy, Er, Ho, Tm, Lu and 
Yb) that has been calcined earlier to a main component of a composite 
oxide of Pb, Ti and Zr that has been calcined earlier, mixing the main 
component and the subsidiary component, and sintering the mixture. 
According to another aspect of the present invention, a method for 
producing a piezoelectric ceramic composition comprises the steps of 
adding a subsidiary component that has been calcined earlier to a main 
component that has been calcined earlier, mixing the main component and 
the subsidiary component, and sintering the mixture. In this method, 
RMnO.sub.3, where R is at least one metal element selected from the group 
consisting of Y, Dy, Er, Ho, Tm, Lu and Yb, is used as the subsidiary 
component. The main component is a composite oxide represented by Formula 
(III): 
EQU Pb(A, Nb).sub.x Zr.sub.y Ti.sub.1-x-y O.sub.3 (III) 
where 0.ltoreq.x.ltoreq.0.05, 0.35.ltoreq.y.ltoreq.0.80, and A is at least 
one metal element selected from the group consisting of Sn, Zn, Ni and Mg. 
The subsidiary component is added to the main component in an amount so 
that the amount of R.sub.2 O.sub.3 is 0.01 to 0.05 mol per mol of the main 
component, and the amount of Mn.sub.2 O.sub.3 is 0.01 to 0.05 mol per mol 
of the main component. 
According to another aspect of the present invention, a piezoelectric 
device comprises the piezoelectric ceramic composition as described above, 
and specifically is used for a piezoelectric ceramic filter, a 
piezoelectric ceramic oscillator, and various sensors. 
Furthermore, the piezoelectric device such as a piezoelectric ceramic 
oscillator and a piezoelectric ceramic filter including a piezoelectric 
oscillating part and an additional capacitive part as one unit is formed 
of the piezoelectric ceramic composition as described above. 
As described above, the piezoelectric ceramic composition of the present 
invention suppresses the change in the resonance frequency due to heat 
shock and the drift thereafter, and thus provides better piezoelectric 
properties than those of a conventional piezoelectric ceramic composition. 
More specifically, the changes in the resonance frequency and the 
capacitance are small when comparing those measured before a heat 
treatment to those measured thereafter. Thus, the present invention 
provides a piezoelectric ceramic composition having excellent heat 
resistance. This piezoelectric ceramic composition has only a small change 
over time in the characteristics, even if a heat treatment is performed at 
250.degree. C. for a short period. Therefore, it is particularly useful in 
view of the quality control in the production process. 
Furthermore, the piezoelectric ceramic composition of the present invention 
provides a piezoelectric device having excellent heat resistance. A 
piezoelectric ceramic filter produced with the piezoelectric ceramic 
composition of the present invention has excellent heat resistance so that 
the shift in the characteristics of the frequency dependence of the filter 
is small when comparing those before and after a heat treatment. 
These and other advantages of the present invention will become apparent to 
those skilled in the art upon reading and understanding the following 
detailed description with reference to the accompanying figures.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Hereinafter, the present invention will be described by way of examples 
with reference to the accompanying drawings. 
EXAMPLE 1 
PbO, Y.sub.2 O.sub.3, MnCO.sub.3, TiO.sub.2 and ZrO.sub.2 were used as 
starting materials and weighed in a predetermined proportion so that a 
composition ratio of x, a, and d in (1-x)PbTi.sub.1-a Zr.sub.a O.sub.3 
--xYMn.sub.d O.sub.1+2d (0&lt;x.ltoreq.0.045, 0.529.ltoreq.a.ltoreq.0.538, 
0.5.ltoreq.d.ltoreq.3.2) is in accordance with that shown in Table 1. The 
material powders were mixed in a ball mill and calcined at 750 to 
900.degree. C. for 2 hours. The material powder was ground in a ball mill 
again, and the obtained powder was compressed and molded into a 
disk-shaped compressed body having a diameter of 13 mm and a thickness of 
1 mm. The compressed body was sintered at 1140 to 1260.degree. C. for 2 
hours. The obtained ceramic was polished so as to have a thickness of 0.3 
mm. Thereafter, electrodes were fabricated by vacuum evaporation of Cr--Au 
on both surfaces of the ceramic. This element was polarized by applying a 
direct electric field of 4 kV/mm between the electrodes in silicone oil at 
100.degree. C. for 30 min. Then, the polarized electrodes were removed, 
and partial electrodes were formed of Cr--Au so as to obtain an energy 
trapping type resonator as shown in FIG. 1. The resonator shown in FIG. 1 
includes a piezoelectric ceramic 1, electrodes 2 and an oscillating part 
(resonant part) 3. 
This sample was placed in an oven at 250.degree. C. for 10 minutes, and the 
changes due to a heat treatment in the resonance frequency, the 
antiresonant frequency, and the capacitance were measured with an 
impedance analyzer. Thus, various properties (dielectric constant, 
dielectric loss tangent, electromechanical coupling coefficient, 
mechanical quality factor) were obtained. Table 1 shows the results. 
TABLE 1 
______________________________________ 
(1 - x)PbTi.sub.1-a Zr.sub.a O.sub.3 - xYMn.sub.d O.sub.1+2d 
Sample .epsilon..sub.33.sup.T / 
No. x d a .epsilon..sub.0 
tan .delta. 
k.sub.p 
k.sub.15 
k.sub.t 
Q.sub.m 
______________________________________ 
1 0.015 1.0 0.529 
931.6 
0.0127 
0.570 
0.634 
0.482 
587 
2 0.015 1.0 0.532 
853.7 
0.0124 
0.570 
0.624 
0.490 
606 
3 0.015 1.0 0.535 
747.5 
0.0120 
0.564 
0.631 
0.491 
626 
4 0.015 1.0 0.538 
646.9 
0.0119 
0.553 
0.622 
0.501 
629 
5 0.015 0.7 0.535 
715.1 
0.0064 
0.579 
0.631 
0.508 
840 
6 0.015 1.4 0.535 
768.5 
0.0183 
0.541 
0.610 
0.483 
483 
7 0.010 1.6 0.535 
638.2 
0.0109 
0.554 
0.631 
0.498 
636 
8 0.020 0.7 0.535 
855.5 
0.0131 
0.565 
0.621 
0.515 
450 
9 0.015 1.4 0.532 
797.1 
0.0003 
0.542 
0.612 
0.479 
537 
10 0.015 1.8 0.532 
819.7 
0.0236 
0.526 
0.608 
0.468 
419 
11 0.015 2.1 0.532 
835.4 
0.0262 
0.520 
0.615 
0.470 
383 
12 0.015 1.4 0.529 
905.9 
0.0183 
0.539 
0.622 
0.480 
497 
13 0.015 1.8 0.529 
870.2 
0.0236 
0.521 
0.615 
0.463 
411 
14 0.015 3.0 0.529 
881.5 
0.0267 
0.510 
0.613 
0.459 
375 
15 0.015 1.4 0.534 
827.5 
0.0185 
0.540 
0.621 
0.476 
467 
16 0.040 0.5 0.535 
895.6 
0.0208 
0.547 
0.624 
0.492 
423 
*17 0.015 3.2 0.529 
902.0 
0.0450 
0.492 
0.562 
0.445 
280 
*18 0.045 0.5 0.535 
898.2 
0.0250 
0.486 
0.551 
0.440 
431 
______________________________________ 
The compositions of samples 1 to 16 have a large coupling coefficient 
k.sub.15 and a large mechanical quality factor (Q.sub.m) of 370 to 840. On 
the other hand, the compositions of samples 17 and 18, which are marked 
with *, have small coupling coefficients, and thus poor characteristics. 
Furthermore, a Cr--Au electrode was formed to obtain an energy trapping 
type piezoelectric device including an additional capacitive part 4 in 
addition to the oscillating part (resonant part) 3, as shown in FIG. 2. 
The characteristics of this sample at temperatures between -20 to 
80.degree. C. were evaluated. Furthermore, the heat resistance of the 
sample was tested by measuring the characteristics before and after the 
heat treatment in which the sample was placed in an oven at 250.degree. C. 
for 10 minutes so as to evaluate the change. As a result, the frequency 
stability of the piezoelectric device formed of the piezoelectric ceramic 
composition of the present invention is better than that of a 
piezoelectric device formed of a conventional material, because the change 
in the frequency was smaller than that of a conventional material. Thus, 
the present invention provides a piezoelectric device having excellent 
heat resistance. 
EXAMPLE 2 
PbO, ZnO, NiO, MgO, Nb.sub.2 O.sub.5, ZrO.sub.2, TiO.sub.2, Y.sub.2 
O.sub.3, Er.sub.2 O.sub.3, Ho.sub.2 O.sub.3, Tm.sub.2 O.sub.3, Lu.sub.2 
O.sub.3, Yb.sub.2 O.sub.3, and Mn.sub.3 O.sub.4 were used as starting 
materials with Fe.sub.2 O.sub.3, Cr.sub.2 O.sub.3, CoO, CuO, and SnO.sub.2 
added, if necessary. These oxides were weighed so as to have composition 
ratios shown in Tables 2 to 4. The material powders were mixed in a ball 
mill and calcined at 750 to 900.degree. C. for 2 hours. The material 
powder was ground in a ball mill again, and the obtained powder was 
compressed and molded into a disk-shaped compressed body having a diameter 
of 13 mm and a thickness of 1 mm. The compressed body was sintered at 1140 
to 1260.degree. C. for 2 hours. The obtained ceramic was polished so as to 
have a thickness of 0.3 mm. Thereafter, electrodes were fabricated by 
vacuum evaporation of Cr--Au on both surfaces of the ceramic. This element 
was polarized by applying a direct electric field of 5 kV/mm between the 
electrodes in silicone oil at 100.degree. C. for 30 min. Then, the 
polarized electrodes were partially removed so that partial electrodes 
were formed of Cr--Au. Thus, an energy trapping type resonator was 
obtained. 
This sample was placed in an oven at 250.degree. C. for 10 minutes, and the 
resonance frequency, the antiresonant frequency, and the capacitance were 
measured with an impedance analyzer before and after the heat treatment so 
as to obtain change ratios. Tables 2 to 4 show the results. 
TABLE 2 
______________________________________ 
(1 - x)Pb(Zn.sub.1/3 Nb.sub.2/3).sub.a Zr.sub.b O.sub.3 - xYMnO.sub.3 
Sam- fr Capacitance 
ple Change Change 
No. x a b c Ratio (%) 
Ratio (%) 
k' 
______________________________________ 
**1 0 0 0.53 0.47 0.98 -8.4 0.34 
2 0.01 0 0.53 0.47 0.09 -2.6 0.33 
3 0.02 0 0.53 0.47 0.06 -0.8 0.32 
4 0.04 0 0.535 
0.465 0.04 -0.9 0.32 
5 0.1 0 0.54 0.46 0.06 -1.1 0.26 
*6 0.15 0 0.545 
0.455 0.22 -1.3 0.18 
7 0.02 0.01 0.52 0.47 0.05 -0.5 0.34 
8 0.02 0.02 0.515 
0.465 0.05 -0.6 0.34 
9 0.02 0.05 0.51 0.44 0.08 -0.7 0.31 
10 0.02 0.1 0.49 0.41 0.02 -1.5 0.3 
*11 0.02 0.15 0.48 0.37 0.4 -2.9 0.26 
12 0.02 0 0.7 0.3 0.04 -0.5 0.22 
13 0.02 0 0.2 0.8 0.04 -0.4 0.21 
14 0.02 0 0 1 0.04 -0.3 0.26 
______________________________________ 
TABLE 3 
__________________________________________________________________________ 
(1 - x)Pb(Zn.sub.1/3 Nb.sub.2/3).sub.a Zr.sub.b Ti.sub.c O.sub.3 - 
xYMnO.sub.3 
fr Capacitance 
Change 
Change 
Sample Ratio 
Ratio 
No. x a b c Additional component 
(%) (%) k' 
__________________________________________________________________________ 
15 0.02 
0 0.535 
0.465 
0.2 wt % Fe.sub.2 O.sub.3 
0.04 
-0.4 0.36 
16 0.02 
0 0.535 
0.465 
0.2 wt % Cr.sub.2 O.sub.3 
0.03 
-0.3 0.35 
17 0.02 
0 0.535 
0.465 
0.6 wt % CoO 
0.04 
-0.4 0.35 
18 0.02 
0 0.535 
0.465 
0.05 wt % CuO 
0.04 
-0.4 0.34 
19 0.02 
0 0.535 
0.465 
0.3 wt % SnO.sub.2 
0.05 
-0.4 0.34 
__________________________________________________________________________ 
TABLE 4 
______________________________________ 
(1 - x)Pb(M.sub.1/3 Nb.sub.2/3).sub.a Zr.sub.b Ti.sub.c O.sub.3 - 
xRMnO.sub.3 
Capaci- 
fr tance 
Change 
Change 
Sample Ratio Ratio 
No. M R x a b c (%) (%) k' 
______________________________________ 
20 Mg Y 0.02 0.02 0.515 
0.465 
0.09 -0.6 0.35 
21 Mg Y 0.02 0.1 0.49 0.41 0.12 -0.9 0.37 
22 Ni Y 0.02 0.02 0.515 
0.465 
0.08 -0.7 0.35 
23 Ni Y 0.02 0.1 0.49 0.41 0.15 -1.1 0.37 
24 Zn Er 0.02 0.02 0.515 
0.465 
0.07 -0.7 0.35 
25 Zn Ho 0.02 0.02 0.515 
0.465 
0.08 -0.9 0.36 
26 Ni Tm 0.02 0.02 0.515 
0.465 
0.07 -0.6 0.35 
27 Zn Lu 0.02 0.02 0.515 
0.465 
0.09 -0.8 0.34 
28 Zn Yb 0.02 0.02 0.51 0.47 0.1 -0.6 0.35 
______________________________________ 
In Tables 2 to 4, the fr change ratio and the capacitance change ratio 
refer to change ratios of the resonance frequency (fr) and the capacitance 
(C) at the time when 24 hours have passed since the heat treatment on the 
basis of those at the time when 30 minutes have passed since the heat 
treatment, respectively. An apparent coupling coefficient k' is calculated 
according to the following equation with values of the resonance frequency 
(fr) and antiresonant frequency (fa) measured at the time when 24 hours 
have passed since the heat treatment. 
EQU k'.sup.2 =(fa.sup.2 -fr.sup.2)/fa.sup.2 
Sample 1 marked with ** in Table 2 is a conventional piezoelectric ceramic 
composition not containing a metal element R nor Mn. As seen from Tables 2 
to 4, other piezoelectric ceramic compositions containing a metal element 
R and Mn provide piezoelectric devices with smaller resonance frequency 
change ratios and smaller capacitance change ratios than those of sample 
1. 
However, sample 6 marked with * in Table 2 has a content rate x of 
YMnO.sub.3 of 0.15, which is relatively large, and has a better resonance 
frequency change ratio and a better capacitance change ratio than those of 
sample 1. However, the apparent coupling coefficient k' is lower. Thus, a 
content rate x is preferably smaller than 0.15, more specifically, 
preferably 0.01 to 0.1, and more preferably 0.015 to 0.05. 
Similarly, sample 11 marked with * in Table 2 has a content rate a of Zn 
and Nb of 0.15, which is relatively large. This sample has a lower 
resonance frequency change ratio and a lower capacitance change ratio than 
those of sample 1, but is not so low as those of other samples. Thus, a 
content rate a is preferably smaller than 0.15, more specifically, 
preferably 0 to 0.1. 
Furthermore, as shown in Table 3, when any one of Fe.sub.2 O.sub.3, 
Cr.sub.2 O.sub.3, CoO, CuO, and SnO.sub.2 was added to 0.98PbZr.sub.0.535 
Ti.sub.0.465 O.sub.3 -0.02YMnO.sub.3, the heat resistance and the 
stability were further improved. The amount of an added oxide shown in 
Table 2 is represented by the ratio (wt %) of the weight of the added 
oxide to that of the whole composition. Fe, Cr, Co, Cu or Sn is preferably 
added in an amount so that the amount of each oxide thereof is 0.01 to 
1.3wt %, most preferably 0.05 to 0.6wt %. 
Furthermore, as shown in Table 4, when Zn is replaced by Mg or Ni, the heat 
resistance was improved. Thus, a piezoelectric device formed of a 
composition comprising a bivalent metal element that forms a composite 
perovskite instead of Zn has the same level of heat resistance and 
stability as a composition comprising Zn. 
Furthermore, as shown in Table 4, when Y is replaced by Er, Ho, Tm, Lu or 
Yb, the heat resistance was improved. Thus, a piezoelectric device formed 
of a composition comprising a trivalent rare earth element instead of Y 
has an improved heat resistance and stability. This advantage is believed 
to result from the fact that Y or a trivalent rare earth element readily 
forms a manganite compound represented by RMnO.sub.3 with Mn. 
The piezoelectric ceramic composition of the present invention is not 
limited to the above-described embodiments. For example, a trace amount of 
impurity or additive may be present, as long as it does not prevent the 
object of the present invention from being achieved. 
EXAMPLE 3 
The same oxides as in Example 2 were used as starting materials and weighed 
so as to have a composition ratio of (1-x)PbZr.sub.b Ti.sub.c O.sub.3 
--xYMnO.sub.3 (0.01.ltoreq.x.ltoreq.0.1, 0.46.ltoreq.b.ltoreq.0.49, 
0.51.ltoreq.c.ltoreq.0.54, b+c=1). Furthermore, Cr.sub.2 O.sub.3 was added 
in an amount of 0.2wt % with respect to (1-x)PbZr.sub.b Ti.sub.c O.sub.3 
--xYMnO.sub.3. These materials were mixed in a ball mill and calcined at 
850.degree. C. for 2 hours. The calcined powder was ground in a ball mill 
again, and the obtained powder was molded into a rectangular sheet having 
a size of 7.times.3 mm and a thickness of 1 mm. The sheet was sintered at 
1170.degree. C. for 2 hours. After sintering, the obtained ceramic was 
polished so as to have a thickness of 0.2 mm. Thereafter, electrodes were 
fabricated by vacuum evaporation of Cr--Au on both surfaces of the 
ceramic. This element was polarized by applying a direct electric field of 
5 kV/mm between the electrodes in silicone oil at 100.degree. C. for 30 
min, and then subjected to a heat treatment at 300.degree. C. for 30 
minutes. Then, the polarized electrodes were partially removed so that Cr 
and Au were formed on a surface of a piezoelectric ceramic 1 to act as 
electrodes 2 and an additional capacitive part (unpolarized part) 4 so as 
to form oscillating parts (resonant parts) 3. Thus, an energy trapping 
type filter as shown in FIG. 3 was obtained. 
This filter was placed in an oven at 250.degree. C. for 10 minutes, and the 
changes in the characteristics of the frequency dependence of the filter 
caused by this heat treatment were measured. As a result, it was confirmed 
that the characteristics of the frequency dependence of the piezoelectric 
ceramic of the present invention using the above-described ceramic 
composition do not change significantly due to the heat treatment, 
compared with that with a conventional composition such as sample 1 in 
Table 2. 
The piezoelectric device of the present invention is not limited to the 
above-described embodiments. For example, the present invention can apply 
to various elements formed of a piezoelectric ceramic composition, such as 
an oscillator, a resonator, piezoelectric sensors, a piezoelectric 
actuator, or a piezoelectric transducer. In order to obtain large 
piezoelectricity, for example, x, b and c in (1-x)PbZr.sub.b Ti.sub.c 
O.sub.3 --xYMnO.sub.3 are preferably in the ranges: 
0.01.ltoreq.x.ltoreq.0.03, 0.52.ltoreq.b.ltoreq.0.54, 
0.46.ltoreq.c.ltoreq.0.48, which is in the vicinity of the morphotropic 
phase boundary, although it is not limited to thereto. 
EXAMPLE 4 
Pb.sub.3 O.sub.4, TiO.sub.2, ZrO.sub.2, Nb.sub.2 O.sub.5,SnO.sub.2, ZnO, 
NiO and MgO, and MnCO.sub.3, Y.sub.2 O.sub.3, Dy.sub.2 O.sub.3, Er.sub.2 
O.sub.3, Ho.sub.2 O.sub.3, and Yb.sub.2 O.sub.3 were used as starting 
material powders. Pb.sub.3 O.sub.4, TiO.sub.2, ZrO.sub.2, Nb.sub.2 
O.sub.5, SnO.sub.2, ZnO, NiO, and MgO were weighed so that Pb(A, Nb).sub.x 
Zr.sub.y Ti.sub.1-x-y O.sub.3 (where A is at least one metal element 
selected from the group consisting of Sn, Zn, Ni and Mg) could have a 
composition ratio shown in Table 5. MnCO.sub.3, Y.sub.2 O.sub.3, Dy.sub.2 
O.sub.3, Er.sub.2 O.sub.3, Ho.sub.2 O.sub.3, and Yb.sub.2 O.sub.3 were 
weighed so that Mn.sub.2 O.sub.3 and R.sub.2 O.sub.3 (where R is at least 
one metal element selected from the group consisting of Y, Dy, Er, Ho and 
Yb) could have composition ratios shown in Table 5 with respect to Pb(A, 
Nb).sub.x Zr.sub.y Ti.sub.1-x-y O.sub.3. Thereafter, pure water was mixed 
with these components, and the mixture was further mixed in a ball mill 
for 17 hours. The mixed powder was dried, and the dried powder was 
calcined at 750 to 900.degree. C. Then, the powder was ground with a ball 
mill again for 15 hours, and the obtained powder (having an average 
particle size of 1.0 to 1.7 .mu.m) was molded into a disk-shaped body 
having a diameter of 13 mm and a thickness of 1 mm. The molded body was 
sintered at 1140 to 1260.degree. C. for 1 hour. After sintering, the 
obtained ceramic was polished so as to have a thickness of 0.3 mm. 
Thereafter, electrodes were fabricated by vacuum evaporation of Cr--Au on 
both surfaces of the ceramic. Then, this element was polarized by applying 
a direct electric field of 3 kV/mm between the electrodes in silicone oil 
at 150.degree. C. for 30 min. The resonance frequency (fr) and the 
antiresonant frequency (fa) of this sample were measured after a heat 
treatment at 150.degree. C. for 30minutes, and compared to those measured 
before the heat treatment. Table 5 shows the results of samples 1 to 29. 
TABLE 5 
__________________________________________________________________________ 
Pb(A, Nb).sub.x Zr.sub.y Ti.sub.1-x-y O.sub.3 + aMn.sub.2 O.sub.3 + 
bY.sub.2 O.sub.3 + cDy.sub.2 O.sub.3 + dEr.sub.2 O.sub.3 + eHo.sub.2 
O.sub.3 + fYb.sub.2 O.sub.3 
fr Change ratio 
fa Change ratio (%) 
Sinter from pre-heat treatment 
from pres-heat 
treatment 
Sam. temperature 
20 min. 
24 hr. 
20 min. 
24 hr. 
No. A x y a b c d e f [.degree. C.] 
k.sub.t 
later later later later 
__________________________________________________________________________ 
* 1 -- 
0 0.53 
0 0 0 0 0 0 1260 0.35 
-1.190 
-0.440 
-1.120 
-0.430 
2 -- 
0 0.53 
0.01 
0.01 
0 0 0 0 1200 0.51 
-0.080 
0.100 0.009 0.096 
3 -- 
0 0.53 
0.02 
0.02 
0 0 0 0 1170 0.50 
0.009 0.038 0.025 -0.001 
4 -- 
0 0.53 
0.03 
0.03 
0 0 0 0 1200 0.43 
0.011 0.009 0.028 0.001 
5 -- 
0 0.53 
0.05 
0.05 
0 0 0 0 1140 0.39 
0.021 0.011 0.033 0.009 
* 6 -- 
0 0.53 
0.06 
0.06 
0 0 0 0 1140 0.33 
1.000 0.230 1.840 0.196 
* 7 -- 
0 0.20 
0.02 
0.02 
0 0 0 0 The sinters were not dense. 
8 -- 
0 0.35 
0.02 
0.02 
0 0 0 0 1200 0.45 
-0.090 
0.095 0.015 0.087 
9 -- 
0 0.60 
0.02 
0.02 
0 0 0 0 1200 0.45 
0.011 0.006 0.041 0.005 
10 -- 
0 0.70 
0.02 
0.02 
0 0 0 0 1200 0.34 
0.019 0.005 0.044 0.003 
11 -- 
0 0.80 
0.02 
0.02 
0 0 0 0 1200 0.33 
0.022 0.006 0.055 0.004 
* 12 -- 
0 0.95 
0.02 
0.02 
0 0 0 0 1200 0.30 
0.993 0.555 0.101 0.346 
13 -- 
0 0.53 
0.02 
0 0.02 
0 0 0 1170 0.50 
0.009 0.019 0.020 0.001 
14 -- 
0 0.53 
0.02 
0 0 0.02 
0 0 1170 0.49 
0.008 0.018 0.023 0.002 
15 -- 
0 0.53 
0.02 
0 0 0 0.02 
0 1170 0.48 
0.009 0.027 0.030 0.003 
16 -- 
0 0.53 
0.02 
0 0 0 0 0.02 
1170 0.49 
0.007 0.033 0.019 0.003 
17 -- 
0 0.53 
0.02 
0.01 
0.01 
0 0 0 1200 0.49 
0.021 0.009 0.041 0.026 
18 -- 
0 0.53 
0.02 
0 0.01 
0.01 
0 0 1200 0.48 
0.008 0.019 0.020 0.015 
19 -- 
0 0.53 
0.02 
0 0 0.01 
0.01 
0 1200 0.50 
0.031 0.011 0.031 0.022 
20 -- 
0 0.53 
0.02 
0 0 0 0.01 
0.01 
1200 0.48 
0.029 0.010 0.044 0.030 
21 -- 
0 0.53 
0.02 
0.01 
0 0.01 
0 0 1200 0.45 
0.029 0.019 0.045 0.004 
22 -- 
0 0.53 
0.02 
0.01 
0 0 0.01 
0 1200 0.46 
0.011 0.021 0.041 0.021 
23 -- 
0 0.53 
0.02 
0.01 
0 0 0 0.01 
1200 0.50 
0.015 0.020 0.044 0.049 
24 -- 
0 0.53 
0.02 
0.01 
0.01 
0.01 
0.01 
0.01 
1200 0.38 
0.025 0.016 0.055 0.050 
25 Sn 
0.05 
0.53 
0.02 
0.02 
0 0 0 0 1260 0.45 
0.023 0.021 0.055 0.050 
26 Zn 
0.05 
0.53 
0.02 
0.02 
0 0 0 0 1260 0.45 
0.011 0.009 0.059 0.045 
27 Ni 
0.05 
0.53 
0.02 
0.02 
0 0 0 0 1260 0.44 
0.012 0.011 0.043 0.041 
28 Mg 
0.05 
0.53 
0.02 
0.02 
0 0 0 0 1260 0.43 
0.025 0.023 0.047 0.044 
* 29 Sn 
0.10 
0.53 
0.02 
0.02 
0 0 0 0 The sinters were not dense. 
__________________________________________________________________________ 
As seen from Table 5, when a subsidiary component of Mn.sub.2 O.sub.3 and 
R.sub.2 O.sub.3 (where R is at least one metal element selected from the 
group consisting of Y, Dy, Er, Ho, and Yb) is added to a main component 
expressed by a general formula: Pb(A, Nb).sub.x Zr.sub.y Ti.sub.1-x-y 
O.sub.3 (where 0.ltoreq.x.ltoreq.0.05, 0.35.ltoreq.y.ltoreq.0.80, and A is 
at least one metal element selected from the group consisting of Sn, Zn, 
Ni and Mg), the change ratios of the resonance frequency and the 
antiresonant frequency and the drift thereafter for the obtained 
piezoelectric ceramic compositions are significantly smaller than those of 
a piezoelectric ceramic composition not comprising the subsidiary 
component of Mn.sub.2 O.sub.3 and R.sub.2 O.sub.8 (sample 1). Moreover, 
the compositions are better than samples marked with * other than sample 1 
in Table 5. 
The same effect was provided when a composite oxide comprising two or more 
metal elements A, such as Pb(Zn.sub.1/6 Sn.sub.1/6 Nb.sub.2/3).sub.0.03 
Zr.sub.0.53 Ti.sub.0.41 O.sub.3, was used. 
EXAMPLE 5 
Pb.sub.3 O.sub.4, TiO.sub.2, ZrO.sub.2, Nb.sub.2 O.sub.5, SnO.sub.2, ZnO, 
NiO, and MgO were used as starting material powders and weighed so that 
Pb(A, Nb).sub.x Zr.sub.y Ti.sub.1-x-y O.sub.3 (where A is at least one 
metal element selected from the group consisting of Sn, Zn, Ni and Mg) 
could have a composition ratio shown in Table 6. Then, pure water was 
mixed thereto, and the mixture was further mixed in a ball mill for 17 
hours. Similarly, MnCO.sub.3, Y.sub.2 O.sub.3, Dy.sub.2 O.sub.3, Er.sub.2 
O.sub.3, Ho.sub.2 O.sub.3, and Yb.sub.2 O.sub.3 were used as starting 
material powders and weighed so that RMnO.sub.3 (where R is at least one 
metal element selected from the group consisting of Y, Dy, Er, Ho and Yb) 
could have a composition ratio shown in Table 6. Then, pure water was 
mixed thereto, and the mixture was further mixed in a ball mill for 17 
hours. Each mixed powder was dried, and the dried powders were calcined at 
750 to 900.degree. C. separately from the other. Then, RMnO.sub.3 (where R 
is at least one metal element selected from the group consisting of Y, Dy, 
Er, Ho and Yb) as a subsidiary component was added in a predetermined 
amount to the main component, Pb(A, Nb).sub.x Zr.sub.y Ti.sub.1-x-y 
O.sub.3 (where A is at least one metal element selected from the group 
consisting of Sn, Zn, Ni and Mg). Thereafter, the powder was ground in a 
ball mill for 15 hours, and the obtained powder (having an average 
particle size of 1.0 to 1.7 .mu.m) was molded into a disk-shaped body 
having a diameter of 13 mm and a thickness of 1 mm. The molded body was 
sintered at 1140 to 1260.degree. C. for 1 hour. The obtained ceramic was 
polished so as to have a thickness of 0.3 mm. Thereafter, electrodes were 
fabricated by vacuum evaporation of Cr--Au on both surfaces of the 
ceramic. This element was polarized by applying a direct electric field of 
3 kV/mm between the electrodes in silicone oil at 150.degree. C. for 30 
min. The resonance frequency (fr) and the antiresonant frequency (fa) of 
this sample were measured after a heat treatment at 150.degree. C. for 30 
minutes, and compared to those measured before the heat treatment Table 6 
shows the results of samples 30 to 54. 
TABLE 6 
__________________________________________________________________________ 
Pb(A, Nb).sub.x Zr.sub.y Ti.sub.1-x-y O.sub.3 + aRMn.sub.2 O.sub.3 
fr Change ratio (%) 
fa Change ratio (%) 
Sinter from pre-heat treatment 
from pre-heat treatment 
Sam. temperature 
20 min. 
24 hr. 
20 min. 
24 hr. 
No. A R x y a [.degree. C.] 
k.sub.t 
later later 
later later 
__________________________________________________________________________ 
* 30 -- 
-- 0 0.53 
0 1260 0.35 
-1.190 
-0.440 
-1.120 
-0.430 
31 -- 
Y 0 0.53 
0.02 
1170 0.52 
-0.077 
0.090 
0.019 0.036 
32 -- 
Y 0 0.53 
0.04 
1140 0.51 
0.023 0.022 
0.025 -0.007 
33 -- 
Y 0 0.53 
0.06 
1170 0.51 
0.031 0.033 
0.018 0.020 
34 -- 
Y 0 0.53 
0.10 
1140 0.41 
0.063 0.050 
0.040 0.031 
* 35 -- 
Y 0 0.53 
0.12 
1140 0.33 
1.210 0.240 
1.740 0.201 
* 36 -- 
Y 0 0.20 
0.04 
The sinters were not dense. 
37 -- 
Y 0 0.35 
0.04 
1170 0.48 
-0.080 
0.088 
0.032 0.033 
38 -- 
Y 0 0.60 
0.04 
1170 0.46 
0.021 0.005 
0.029 0.013 
39 -- 
Y 0 0.70 
0.04 
1170 0.41 
0.022 0.019 
0.040 0.023 
40 -- 
Y 0 0.80 
0.04 
1170 0.35 
0.022 0.006 
0.055 0.004 
* 41 -- 
Y 0 0.95 
0.04 
1170 0.31 
1.393 0.335 
0.101 0.345 
42 -- 
Y 0 0.53 
0.04 
1170 0.50 
0.016 0.019 
0.020 0.019 
43 -- 
Y 0 0.53 
0.04 
1140 0.52 
0.020 0.018 
0.053 0.033 
44 -- 
Y 0 0.53 
0.04 
1140 0.49 
0.022 0.021 
0.030 0.003 
45 -- 
Y 0 0.53 
0.04 
1140 0.50 
0.050 0.041 
0.069 0.041 
46 -- 
Dy 0 0.53 
0.04 
1200 0.51 
0.021 0.009 
0.041 0.026 
47 -- 
Er 0 0.53 
0.04 
1200 0.51 
0.008 0.019 
0.020 0.015 
48 -- 
Ho 0 0.53 
0.04 
1200 0.50 
0.051 0.041 
0.031 0.022 
49 -- 
Yb 0 0.53 
0.04 
1200 0.52 
0.059 0.040 
0.034 0.030 
50 Sn 
Y 0.05 
0.53 
0.04 
1260 0.50 
0.012 0.011 
0.035 0.030 
51 Zn 
Y 0.05 
0.53 
0.04 
1260 0.51 
0.021 0.012 
0.059 0.046 
52 Ni 
Y 0.05 
0.53 
0.04 
1260 0.52 
0.013 0.018 
0.047 0.041 
53 Mg 
Y 0.05 
0.53 
0.04 
1260 0.53 
0.022 0.008 
0.057 0.054 
* 54 Sn 
Y 0.10 
0.53 
0.04 
The sinters were not dense. 
__________________________________________________________________________ 
Herein, an oxide expressed by a general formula: Pb(A, Nb).sub.x Zr.sub.y 
Ti.sub.1-x-y O.sub.3 (where 0.ltoreq.x.ltoreq.0.05, 
0.35.ltoreq.y.ltoreq.0.80, and A is at least one metal element selected 
from the group consisting of Sn, Zn, Ni and Mg) that has been calcined 
beforehand is a main component of a piezoelectric ceramic composition. 
RMnO.sub.3 (where R is at least one metal element selected from the group 
consisting of Y, Dy, Er, Ho, and Yb) that has been calcined beforehand is 
a subsidiary component. The subsidiary component was added to the main 
component in an amount so that the amounts of Mn.sub.2 O.sub.3 and R.sub.2 
O.sub.3 were in the range from 0.01 to 0.05mol per mol of the main 
component. Then, the mixture was sintered so as to obtain a piezoelectric 
ceramic composition (shown in Table 6 as samples not marked with *). As 
seen from Table 6, the change ratios of the resonance frequency and the 
antiresonant frequency and the drift after the heat treatment of the 
obtained piezoelectric ceramic compositions are significantly smaller. 
Moreover, the compositions had a high electromechanical coupling 
coefficient (k.sub.t). 
The same effect was provided when a composite oxide comprising two or more 
metal elements A, such as Pb(Zn.sub.1/6 Sn.sub.1/6 Nb.sub.2/3).sub.0.03 
Zr.sub.0.53 Ti.sub.0.41 O.sub.3, was used. 
EXAMPLE 6 
PbO, Y.sub.2 O.sub.3, ZnO, NiO, MgO, Nb.sub.2 O.sub.5, TiO.sub.2, 
ZrO.sub.2, and MnCO.sub.3 were used as starting materials with Fe.sub.2 
O.sub.3, Cr.sub.2 O.sub.3, CoO, CuO, and SnO.sub.2 added, if necessary. 
PbO, Y.sub.2 O.sub.3, ZnO, NiO, MgO, Nb.sub.2 O.sub.5, TiO.sub.2, 
ZrO.sub.2, and MnCO.sub.3 were weighed so that Pb(Y.sub.(1-x)/2 Mn.sub.x/2 
Nb.sub.1/2).sub.a (M.sub.1/3 Nb.sub.2/3).sub.b Zr.sub.c Ti.sub.d O.sub.3 
(where M is at least one metal element selected from the group consisting 
of Zn, Ni and Mg) could have a composition ratio shown in Table 7. 
Furthermore, Fe.sub.2 O.sub.3, Cr.sub.2 O.sub.3, CoO, CuO, or SnO.sub.2 
was added, if necessary, in a weight ratio shown in Table 7 with respect 
to Pb(Y.sub.(1-x)/2 Mn.sub.x/2 Nb.sub.1/2).sub.a (M.sub.1/3 
Nb.sub.2/3).sub.b Zr.sub.c Ti.sub.d O.sub.3. Then, these components were 
mixed in a ball mill and then calcined at 750 to 900.degree. C. for 2 
hours. Then, the material powder was ground with a ball mill. The obtained 
powder was compressed and molded into a disk-shaped compressed body having 
a diameter of 13 mm and a thickness of 1 mm. The compressed body was 
sintered at 1170 to 1290.degree. C. for 2 hours. After sintering, the 
resulting ceramic was polished so as to have a thickness of 0.3 mm. 
Thereafter, electrodes were fabricated by vacuum evaporation of Cr--Au on 
both surfaces of the ceramic. This element was polarized by applying a 
direct electric field of 5 kV/mm between the electrodes in silicone oil at 
100.degree. C. for 30 min. The polarized electrodes were partially removed 
so that Cr--Au electrodes were formed. Thus, an energy trapping type 
resonator was obtained. The resonator was placed in an oven at 250.degree. 
C. for 10 minutes. The resonance frequency (fr), the antiresonant 
frequency (fa), the apparent coupling coefficient (k') and the capacitance 
(C) of the resonator were measured by an impedance analyzer before and 
after the heat treatment. Table 7 shows the results. 
TABLE 7 
__________________________________________________________________________ 
fr Capacitance 
Change 
Change 
Sam. Ratio 
Ratio 
No. x a b c d additive 
(%) (%) k' 
__________________________________________________________________________ 
Pb(Y.sub.1-x)/2 Mn.sub.x/2 Nb.sub.1/2).sub.a (Zn.sub.1/3 Nb.sub.2/3).sub.b 
Zr.sub.c Ti.sub.d O.sub.3 + additive 
* 1 0 0 0 0.53 
0.47 
-- 0.98 
-8.4 0.34 
2 0.5 
0.02 
0 0.52 
0.46 
-- 0.11 
-2.4 0.33 
3 0.5 
0.05 
0 0.5 
0.45 
-- 0.042 
-0.47 0.32 
* 4 1 0.05 
0 0.5 
0.45 
-- 1.1 -6.4 0.35 
5 0 0.05 
0 0.5 
0.45 
-- 0.45 
-1.4 0.33 
6 0.5 
0.1 
0 0.47 
0.43 
-- 0.062 
-0.32 0.29 
* 7 0.5 
0.18 
0 0.42 
0.4 
-- 0.08 
-0.48 0.15 
8 0.5 
0.04 
0.01 
0.49 
0.46 
-- 0.046 
-0.45 0.34 
9 0.5 
0.04 
0.02 
0.49 
0.45 
-- 0.051 
-0.48 0.35 
10 0.5 
0.04 
0.05 
0.47 
0.44 
-- 0.081 
-0.55 0.31 
11 0.5 
0.04 
0.1 
0.43 
0.43 
-- 0.17 
-0.84 0.29 
* 12 0.5 
0.04 
0.2 
0.37 
0.39 
-- 0.41 
-2.2 0.25 
13 0.5 
0.02 
0 0.68 
0.3 
-- 0.038 
-0.38 0.22 
14 0.5 
0.02 
0.05 
0.2 
0.73 
-- 0.036 
-0.35 0.21 
15 0.5 
0.02 
0.05 
0 0.93 
-- 0.037 
-0.34 0.26 
16 0.5 
0.04 
0.01 
0.49 
0.46 
0.2 wt % Fe.sub.2 O.sub.3 
0.038 
-0.42 0.36 
17 0.5 
0.04 
0.01 
0.49 
0.46 
0.2 wt % Cr.sub.2 O.sub.3 
0.032 
-0.32 0.35 
18 0.5 
0.04 
0.01 
0.49 
0.46 
0.6 wt % CoO 
0.035 
-0.35 0.35 
19 0.5 
0.04 
0.01 
0.49 
0.46 
0.05 wt % CuO 
0.041 
-0.36 0.34 
20 0.5 
0.04 
0.01 
0.49 
0.46 
0.3 wt % SnO.sub.2 
0.04 
-0.38 0.34 
Pb(Y.sub.(1-x)/2 Mn.sub.x/2 Nb.sub.1/2).sub.a (Ni.sub.1/3 Nb.sub.2/3).sub. 
b Zr.sub.c Ti.sub.d O.sub.3 + additive 
21 0.5 
0.04 
0.02 
0.49 
0.45 
-- 0.072 
-0.58 0.35 
22 0.5 
0.04 
0.09 
0.44 
0.43 
-- 0.18 
-0.86 0.37 
Pb.sub.(Y.sub.(1-x)/2 Mn.sub.x/2 Nb.sub.1/2).sub.a (Mg.sub.1/3 Nb.sub.2/3) 
.sub.b Zr.sub.c Ti.sub.d O.sub.3 + additive 
23 0.5 
0.04 
0.02 
0.49 
0.45 
-- 0.084 
-0.52 0.34 
24 0.5 
0.04 
0.09 
0.44 
0.43 
-- 0.018 
-0.88 0.36 
__________________________________________________________________________ 
As seen from Table 7, the piezoelectric ceramic compositions not marked 
with * in Table 7 have smaller changes in the piezoelectric properties, 
when comparing those before and after the heat treatment. Thus, the heat 
resistance and the stability of the piezoelectric properties were better 
than those of a conventional piezoelectric material (sample 1). 
Furthermore, a composition (sample 4) with x=1, which means that the 
composition does not comprise Y, does not have small capacitance change 
ratios. 
A composition (sample 7) with a=0.18, which represents a content ratio of 
Y.sub.(1-x)/2 Mn.sub.x/2 Nb.sub.1/2, has a smaller apparent coupling 
coefficient. 
A composition (sample 12) with b=0.2, which represents a content ratio of 
Zn.sub.1/3 Nb.sub.2/3, has a relatively large capacitance change ratio. 
In Pb(Y.sub.1/2 Mn.sub.1/2 Nb.sub.1/2).sub.0.04 (Zn.sub.1/3 
Nb.sub.2/3).sub.0.01 Zr.sub.c Ti.sub.d O.sub.3 (where 
0.ltoreq.c.ltoreq.0.68, 0.3.ltoreq.d.ltoreq.0.93), the compositions having 
c and d in the ranges: 0.47.ltoreq.c.ltoreq.0.51, and 
0.44.ltoreq.d.ltoreq.0.48 have relatively large piezoelectricity, and 
therefore preferably used as a piezoelectric ceramic material. 
Furthermore, in the compositions comprising any one of Fe.sub.2 O.sub.3, 
Cr.sub.2 O.sub.3, CoO, CuO, and SnO.sub.2 added to Pb(Y.sub.(1-x)/2 
Mn.sub.x/2 Nb.sub.1/2).sub.a (Zn.sub.1/3 Nb.sub.2/3).sub.b Zr.sub.c 
Ti.sub.d O.sub.3, the heat resistance and the stability were further 
improved by changing the amount of the addition so that the amount of the 
metal element to be substituted was adjusted. 
Even if Zn is replaced by another bivalent transition metal element such as 
Mg and Ni, as long as the element forms a composite perovskite, the same 
level of heat resistance and stability will be obtained with respect to 
examples of conventional piezoelectric materials. 
EXAMPLE 7 
PbO, Y.sub.2 O.sub.3, ZnO, Nb.sub.2 O.sub.5, TiO.sub.2, ZrO.sub.2, and 
MnCO.sub.3 were used as starting materials with Cr.sub.2 O.sub.3 added. 
PbO, Y.sub.2 O.sub.3, ZnO, Nb.sub.2 O.sub.5, TiO.sub.2, ZrO.sub.2, and 
MnCO.sub.3 were weighed so as to have a composition ratio of 
Pb(Y.sub.(1-x)/2 Mn.sub.x/2 Nb.sub.1/2).sub.a (Zn.sub.1/3 
Nb.sub.2/3).sub.b Zr.sub.c Ti.sub.d O.sub.3 (where 0.ltoreq.x&lt;1.0, 
0.01.ltoreq.a.ltoreq.0.15, 0.ltoreq.b&lt;0.2, 0.ltoreq.c.ltoreq.0.68, 
0.3.ltoreq.d.ltoreq.0.93, and a+b+c+d=1). Cr.sub.2 O.sub.3 was weighed so 
that the amount of Cr.sub.2 O.sub.3 became 0.2wt % with respect to 
Pb(Y.sub.(1-x)/2 Mn.sub.x/2 Nb.sub.1/2).sub.a (Zn.sub.1/3 
Nb.sub.2/3).sub.b Zr.sub.c Ti.sub.d O.sub.3. Then, these components were 
mixed in a ball mill and then calcined at 850.degree. C. for 2 hours. 
Then, the material powder was ground in a ball mill until the average 
particle diameter became 0.5.mu.m or less. The obtained powder was molded 
into a rectangular sheet having a size of 7.times.3 mm and a thickness of 
1 mm. The sheet was sintered at 1200.degree. C. for 2 hours. After 
sintering, the resulting ceramic was polished so as to have a thickness of 
0.2 mm. Thereafter, electrodes were fabricated by vacuum evaporation of 
Cr--Au on both surfaces of the ceramic. This element was polarized by 
applying a direct electric field of 5 kV/mm between the electrodes in 
silicone oil at 100.degree. C. for 30 min. The polarized electrodes were 
partially removed so that Cr--Au electrodes were formed. Thus, an energy 
trapping type filter including a resonant part 3 and an additional 
capacitive part 4, as shown in FIG. 3, was obtained. The element was 
placed in an oven at 250.degree. C. for 10 minutes. The characteristics of 
the frequency dependence of the filter were measured before and after the 
heat treatment so as to evaluate a change. As a result, the 
characteristics of the frequency dependence of the filter formed of the 
piezoelectric ceramic composition of the present invention have a smaller 
change in the comparison of those before and after the heat treatment than 
that of a conventional piezoelectric ceramic material. Thus, the present 
invention can provide a piezoelectric ceramic filter having excellent heat 
resistance. 
The invention may be embodied in other forms without departing from the 
spirit or essential characteristics thereof. The embodiments disclosed in 
this application are to be considered in all respects as illustrative and 
not limiting. The scope of the invention is indicated by the appended 
claims rather than by the foregoing description, and all changes which 
come within the meaning and range of equivalency of the claims are 
intended to be embraced therein.