JPH03150264A - Piezoelectric ceramic and production thereof - Google Patents

Abstract

PURPOSE:To obtain piezoelectric ceramics having small crystal grain size in suppressed grain growth in burning by adding a specific amount of Mn to raw material powder of piezoelectric ceramics of Pb-Sn-Nb-Ti-Zr-O system, calcining the mixture and adding a prescribed amount of SiC thereto when pulverized. CONSTITUTION:Raw material powder is prepared so as to afford piezoelectric ceramics having a composition expressed by the formula (x+y+z=1; x=0.01-0.2; y=0.01-0.75; z=0.05-0.875). Mn of 0.03-0.5wt.%, expressed in terms of MnO2 is added and mixed with the raw material powder and the mixture is calcined and then 0.01-0.5wt.% SiC is added thereto when pulverized. Then the pulverized mixed powder is formed at high pressure and burned at high temperature to provide the piezoelectric ceramics. Thereby the added SiC is effectively left until time when burned and grain growth in burning is suppressed. Consequently, reliability of product obtained by application of the piezoelectric ceramics can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a piezoelectric ceramic used as an electromechanical energy conversion element and a method for manufacturing the same.

Conventional technology P b (S n +isN bz3) xT i v
It is well known from Japanese Unexamined Patent Publication No. 44-66720 that a piezoelectric ceramic obtained by dissolving Mn02 in a ZrzO3-based piezoelectric ceramic has high piezoelectricity. Conventionally, these piezoelectric ceramics have been made using the following method. That is, PbO, Sn02. Nb203゜T
io! , Z r02. After blending MnCO3 to a predetermined composition and mixing with a ball mill etc.,
Calcinate at 00℃ to Pb (Sn+lsNbzs)xTiyZrzos+a
A solid solution of wt% Mn02 was obtained, further ground with a ball mill, etc., molded into a predetermined shape, and then heated at 1100°C to 1250°C.
It was to be fired at ℃.

Problems to be Solved by the Invention With such conventional compositions and manufacturing methods, there was a problem that the crystal grain size of the sintered body became large.

As the crystal grain size of the sintered body increases, the pores also become larger, which reduces the mechanical strength of the sintered body and reduces the reliability of the product.Especially in products that apply surface acoustic waves, the electrode width becomes smaller. The narrowness causes defects in the electrodes. The present invention solves this problem, and aims to obtain a dense piezoelectric ceramic having a small crystal grain size.

Means for Solving the Problems In order to solve the above problems, the present invention uses Pb(Sn +
13Nbzls) x TiyZrzo3 (However, X +
y + z = 1, z = 0.01~0.2゜y =
o, 01-0.75. z=0.05~0.875)
Convert n to Mn02 to 0.03, 5wt%.

This paper proposes piezoelectric ceramics to which 0.01 to 0.5 wt% of SiC is added. Furthermore, Pb (Snt
/sNbt/s)xTiyZrz 03 (However)
(+y+z=1, x=0.01~0.2゜y=0.0
1-0.75. After mixing and calcining raw material powder adjusted to have a composition in which 0.03 to 5 wt% of Mn was added in terms of Mn02 to z = 0.05 to (L875)-, SiC was added during pulverization. (It is proposed to add 101 to 0.5 wt%.

Effect: Due to the composition of the piezoelectric ceramic described above and the method of manufacturing it described above, SiC suppresses the grain growth of the piezoelectric ceramic during firing, making it possible to obtain a piezoelectric ceramic having a small crystal grain size.

EXAMPLE Below, the implementation of the present invention will be described. PbO, Sn0 with chemical purity of 99% or more as raw materials
2, Nb203, T i02. Zr02°MnCO3 was weighed to have a predetermined composition and mixed in a ball mill. The mixed powder was calcined at 850°C and then ground in a ball mill. At the time of this grinding, chemically pure S is 99%.
A predetermined amount of iC powder was added.

The obtained pulverized mixed powder was molded at a pressure of 1000 kg/cj and fired at a temperature of 1100°C to 1250°C.

The obtained sintered body was processed into a disk having a diameter of 15 m and a thickness of 0.5 m, and silver electrodes were baked on the upper and lower surfaces of the disk. The disk with baked silver electrodes was immersed in silicone oil at 100° C., and polarization was performed by applying a potential difference of 1.5 kV between the upper and lower silver electrodes of the disk for 30 minutes. Electrical properties were measured 24 to 36 hours after polarization. The measurement method and calculation of each electrical property are based on the standards of the Electronic Materials Industries Association (EMAS6001-60
07). Table 1 shows the electrical properties and crystal grain sizes of each composition obtained by the above method. In addition, ε33”/ε0 in the table
is the dielectric constant in the same direction as the polarization direction, kp is the electromechanical coupling coefficient of radial vibration, and d is the crystal grain size of the sintered body determined by the intercept method. It was determined from a sintered body fired under firing conditions that maximized the density.

Below c Margin》 <13 1 Table> Mn02 SiCd Nh x y zm amount Added amount
e3%/an kp(-%) (wt%)
(μm)”°°0.030300
0.165.01-2
0.01 295 0.15 4.31
-3 (1
12900, 153, 11-40, 52840, 142
,2 2-10,010,470,520,5012900,
55 low 02-2
0.01 1287 (1545,42-30
,112800,533,9 2-40,512730,513,O Mn02 SiCd Nhxyzjl Physical amount Added amount g31/g@kp
(mX) (wt%) (μm)4
-2 0.01 11
96 0.55 6.64-3
0.1 1190 0.54 5.415
-110.1210-0110.8710.03101
36010. January 8,01° Q, 502.006”°
°°.

Low 2 0.01 6
67 (1357,0 low 3
(11662 (1345, 9 row 4
0.5 656
(1334,28-10,20,430,3?
1.0 0 1250 0.58 9.78-2
0.01
1247 0.57 8.58-3
0.1 1240 0.
56 7.19-::i 0.58820.
378.19-
0.7 816 0.32 7.0 This shows a comparative example.

As shown in Table 1.

Pb (Sn+13Nb21s)xT iyZ rz0
By adding SiC to 3+awt%R/1 n O2, the crystal grain size of the sintered body can be significantly reduced.

This is because SiC forms a solid solution in the piezoelectric ceramic, which is an oxide, and thus suppresses grain growth during sintering of the piezoelectric ceramic. However, if the amount of SiC added is less than 0.01 wt% If SiC is added, no effect is observed, and if it exceeds 0.5 wt%, the crystal grain size becomes smaller but the electrical properties deteriorate, which is not preferable. A comparison is shown in Table 2.

<Table 2> Is i C addition period 33"1501 kp l
d (μm month when mixing 1119310.5416.31
1 During crushing 11184 +0.5214.21 (However, x=0.06.y=0.47.z=0.47 and Mn0
2 addition amount 1, Owt%, SiC addition amount 0.5wt%) As shown in Table 2, when SiC is added during pulverization, powder growth is suppressed and the crystal grain size of the sintered body becomes smaller. This is because if added at the time of mixing, SiC will be oxidized during calcination and will change from solid solution Si02 in the piezoelectric ceramics, so SiC, which should suppress grain growth during sintering of the piezoelectric ceramics, will This is because it is difficult to remain until firing. Furthermore, regarding the composition of piezoelectric ceramics, JP-A-44-66720 describes a highly stable region C, but within this region, compositions with X greater than 0.2 result in too large grain growth; Since the effect of the invention was small, it was excluded from the present invention.

As above the effect of the invention, P b (S nItsN bzis)
xT iyZrz03 (However, x+y+z=1,
x=0.01-0.2. y=0.01-0.75. z=
0.05~0.875) by converting Mn to Mn02
．． 03-5 wt%, 0.01-0.5wt of SiC
% added to the composition, SiC suppresses grain growth during firing of piezoelectric ceramics, resulting in piezoelectric ceramics with small crystal grain sizes. Furthermore, Pb (Sn+13Nbz3)xTiyZrz03 (however, x+y+z=1, x=0.01~0.2゜y=
o, 01-0.75. z=0.05~0.875)
After mixing and calcining the raw materials adjusted to have a composition in which 0.03 to 5 wt% of n is added in terms of Mn02, 0.01 to 0.5 wt% of SiC is added during pulverization. remains effectively until firing, suppressing grain growth during firing, and yielding piezoelectric ceramics with small crystal grain sizes. Therefore, the reliability of products using piezoelectric ceramics is improved, and at the same time, it becomes possible to use surface acoustic waves.

[Brief explanation of the drawing]

Figure 1 is a composition diagram showing the piezoelectric ceramic of the present invention, Figure 2 is a composition diagram showing the piezoelectric ceramic of the present invention.
The figure is a diagram showing the manufacturing process of piezoelectric ceramics. Name of agent: Patent attorney Shigetaka Awano and 1 other person 1st rI!
JPb(5-A SbA)03 Fig. 2 1 Grinding 1 1 Processing 1 1 Electrode position 1

Claims (2)

[Claims] (1) Pb(Sn_1_/_3Nb_2_/_3)x
Ti_YZ_r_zO_3 (where x+y+z=1, x=0.01-0.2, y=0.01-0.75, z
= 0.05 to 0.875), Mn is converted to MnO_2, 0.03 to 5 wt%, and SiC is 0.01 to 0.5 wt%.
Piezoelectric ceramics characterized by the addition of %. (2) Pb(Sn_1_/_3Nb_2_/_3)_
xTi_YZ_r_zO_3 (x+y+z=1
So, z=0.01~0.2, y=0.01~0.75,
z = 0.05 to 0.875) and 0.03 to 5 wt% of Mn (calculated as MnO_2) was mixed and calcined, and then 0.0 of SiC was added during pulverization.
A method for producing piezoelectric ceramics, characterized by adding 1 to 0.5 wt%.