JPH03257882A - Pbtio3 solid solution and manufacture thereof - Google Patents

Abstract

PURPOSE:To equip the crystal axes of an axis and a c axis on each quadrangular side of a single particle so as to get a material for a piezoelectric element wherein the axial directions of crystals are put in order by adding La2O3 and MnO2 at the same time to PbTiO3 powder, and wetly mixing them under existence of ethanol, and then baking it. CONSTITUTION:Using PbTiO3 powder, which is obtained by mixing PbO and TiO2 by equal mols as the starting material and calcining them, La2O3 and MnO2 are added to this at the same time, and those are mixed and weighed so that it may be the specified mol. ratio, and to do the slid reaction uniformly, those are wetly mixed under the existence of ethanol. MnO2 is added to prevent the bulking of the crystals and decrease electric loss (dielectric loss) and mechanical loss. After the wet mixture under existence of ethanol, those are dried for three hours at 80 deg.C. And this is baked for twelve hours at 850 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a PbTi0° solid solution whose crystal axes are aligned in the same direction, which is obtained using PbTiOs powder as a starting material, and a method for producing the same.

[Conventional technology]

Sintered bodies of perovskite compounds, especially titanium-containing perovskite compounds based on barium titanate, lead titanate, or lead titanate-zirconate, have piezoelectric, dielectric,
It is also widely used as a pyroelectric application component.

In these materials, those whose crystal axes are aligned in a certain direction have high performance electrical properties.
It has been attracting attention and research and development for a long time. Among them, lead titanate has a large crystal anisotropy below the Curie point (490°C), so the crystal grains separate at grain boundaries after sintering. It has been difficult to sinter and produce highly pure ceramics that are resistant to corrosion. Furthermore, lead titanate has a large coercive force and is difficult to polarize, which is another reason why it has not been put into practical use for a long time.

Therefore, research was conducted to create high-density ceramics by adding additives to lead titanate that are highly effective in suppressing grain growth and increasing the bonding strength of grain boundaries. As a result, (P b O+ T i Oz) was used as the starting material, and this was combined with L a 2/3 T i O3 or LazO3 and M
By simultaneously adding nO□, practical lead titanate piezoelectric ceramics have been developed that have high density, high mechanical strength, and high resistance that can withstand polarization treatment at high temperatures and high electric fields.

[Problem to be solved by the invention]

However, the lead titanate piezoelectric ceramics obtained by the conventional manufacturing method described above have an average particle size of 03 to 0.5 μm.
They are isodirectional particles, and even if they are molded and sintered, they have the problem that only those whose crystal axes do not point in a fixed direction (non-oriented) can be obtained.

[Means to solve the problem]

In order to solve the above-mentioned problem, the PbTiC1+ solid solution according to the invention of claim 1 uses P b Ti O3 powder as a starting material and has crystal axes of a-axis and c-axis on each square face in a single particle. It is characterized by having the following.

Furthermore, P b T i 03 according to the invention of claim 2
In order to solve the above problems, the solid solution manufacturing method
b TiO: + Using the powder as a starting material, PbTiO3
To La 20. and MnO2 are added at the same time, wet mixed in the presence of ethanol, and fired to facilitate grain growth into cubic shapes.

[For production]

In the configuration of the invention of claim 1, the a-axis and the C
Since the crystal axes are oriented in the axial direction, it can be used as a material for manufacturing a piezoelectric element whose crystal axes are aligned in the same direction, and the element can be manufactured easily.

Further, in the structure of the invention of claim 2, PbTi
When 01+ powder is used as a starting material, as the amount of LazO:+ added increases, grains can easily grow into cubic shapes.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

The PbTiO3 solid solution according to the present invention uses P as a starting material.
PbTiO3 powder obtained by mixing and calcining bO and TiO□ in equal molar proportions was used, and La20. and MnO
□ is added at the same time, thereby producing lead titanate piezoelectric ceramics with high density, high mechanical strength, and high resistance that can withstand polarization treatment at high temperatures and high electric fields. The above PbTi 03 , LazO3 (manufactured by Kojundo Kagaku Co., Ltd., 99.
9% sample), and MnO□ (Kojundo Kagaku, 99.
The compounding relationship of 9% sample) was varied based on the following basic formula (1), and the starting materials were Pb0 (manufactured by Wako Pure Chemical Industries, special grade reagent) and TiO□ (manufactured by Fuji Titanium, 99.9% sample). compared to the case where

(1-y) [(1-X)PbTi03+xLazz+T
iO3]+yMnOz...a) However, 0.04≦X
≦0.10 and y≦0.016 In basic formula (1),
The value of y is 0.01, and the value of X is 0.05.0.07.
Corresponding to each value of 0.10, 1, the starting materials are PbO and T
When iOz, the starting material is PbTi0. Two types of bound samples were prepared as shown in Table 1 (see Table 1).

The above samples I and (2) both use each starting material as the main raw material, add La, O, and MnO□ at the same time, and mix and weigh them at a predetermined molar ratio to ensure a uniform solid reaction. wet mix in the presence of ethanol. The above MnO is added to prevent crystal coarsening and reduce electrical loss (dielectric loss) and mechanical loss.

After wet mixing in the presence of ethanol, drying at 80°C for 3 hours. Then, put this in a platinum crucible and hold it at 85°.
Bake at C for 12 hours. At this time, the platinum crucible is fired while being set in a larger magnesia crucible with a lid. This is to avoid evaporation of lead oxide during firing.

The products fired as described above were pulverized and analyzed for X-ray diffraction patterns based on different starting materials, and observed using a scanning electron microscope (SEM). The results will be explained below.

Figure 1 (a) to (C) and Figure 2 (a) to
This will be explained below based on (c). Note that after filling each sample into a recess provided on a sample holder (not shown) such as glass and fixing it with a slide glass,
An X-ray diffraction pattern was obtained for each sample.

In the case of the above I (starting materials are PbO and TiO□), almost the same diffraction pattern was obtained regardless of the value of X, as shown in FIGS. 1(a) to (c).

On the other hand, in the case of the above (the starting material is PbTi0s), the second
As shown in Figures (a) to (C), as the value of It can be seen that the intensity of the line increases. For convenience, the a-axis diffraction lines with respect to the X-ray irradiation direction are (100) and (200), and a
The axial diffraction lines are represented by (001) and (002), respectively. Further, FIG. 3 shows the difference between I and ■ as the a-axis and the degree of orientation of the a-axis, and the dependence on the value of X is plotted. However, the non-oriented sample used here was JCPDS card 6-0452 (PbTi
Os, Tetragonal).

As shown in FIG. 3, it is clearly observed that the degree of orientation of the H sample increases as the value of X increases. This is because P b T i O3 was oriented in the a-axis and in the direction of the a-axis due to its firing. Note that the a-axis diffraction line with respect to the X-ray irradiation direction is expressed as (h
oo), the a-axis diffraction line is (001), and for each sample, the (hoo) plane (a-axis) for Σ(■hkL), which is the algebraic sum of the integrated intensities of all the diffraction lines, and ( Σ(I
H. The degree of orientation F of each sample is calculated by the following formula (2), where P is the ratio of +I0°, ) and Po is the ratio of that of a sample whose crystal axis is not oriented (non-oriented sample). (Lotgering method).

F= (P-Po)/(1-P,)...(2
)Next, as mentioned above, the shape changes at the particle level, not at the atomic level, are shown in Figures 4 and 5.
The following description will be made based on a SEM photograph taken using a scanning electron microscope (SEM).

As shown in Fig. 4, in the case of the sample (■), the average particle size of the lead titanate sintered body is 0.3 μm to 0.5 μm, whereas in the case of As shown, it was confirmed that the average particle size was 3 μm to 5 μm, which was about 10 times that of I. Furthermore, in the case of the sample (■), all the grains were angular, and during the grain growth process, which was about 10 times that of the case (■), the a-axis and the a-axis were selectively oriented in the direction of the cube surface. It is considered to be a thing.

From the above, since the orientation of the crystal axis depends on the value of X, the La20. It can be seen that this has the effect of imparting translucency to PZT (lead zirconate titanate), and also has the effect of facilitating grain growth into a cubic shape.

When the sintered body of lead titanate having the a-axis and the a-axis orientation obtained by firing as described above is crushed, a calcined powder is obtained. Since this calcined powder has no plasticity, it is mixed with a binder such as an aqueous polyvinyl alcohol solution, granulated into aggregates, sized, and then molded by a pressing method or the like. Further, after firing the molded product and processing it into a predetermined size, a piezoelectric element whose crystal axes are aligned in the same direction can be obtained by performing a polarization treatment. In addition, the polarization treatment is performed at 100°C ~ 2
This is done by applying a direct current voltage of 2 to 6 kilovolts per millimeter at a temperature of 00''C for several minutes to several hours.

In this way, a lead titanate piezoelectric element manufactured based on a solid solution of lead titanate having the a-axis and a-axis orientation has a high dielectric constant because the crystal axes are aligned, and is used, for example, in various capacitors. It can be used as In addition, products that utilize the piezoelectricity of lead titanate include blood pressure monitor pickups, accelerometer pickups, knock sensors, piezoelectric spark elements, piezoelectric elements for photographic flash activation, ultrasonic microphones, ultrasonic vibrators for fish finders, Examples include piezoelectric buzzer elements and piezoelectric tuning fork filters. Furthermore, there are infrared sensors and the like that utilize the pyroelectricity (thermal function) of lead titanate. In addition, optical shutters, flash blocking glasses, etc. that utilize the electro-optical functionality of lead titanate
Examples include stereoscopic television glasses and image storage display devices.

Table 1 [Effects of the Invention] The PbTiO3 solid solution according to the invention of claim 1 is as described above. It uses PbTiO3 powder as a starting material, and has a structure in which a single particle has an a-axis and an a-axis crystal axis on each square surface.

Moreover, as described above, the method for producing a PbTiOz solid solution according to the invention of claim 2 uses PbTjO.

Using powder as a starting material, L a , 0° and MnO are simultaneously added to PbTiOs, wet mixed in the presence of ethanol, and fired to facilitate grain growth into a cubic shape.

In the configuration of the invention of claim 1, the a-axis and the
Since it has axial orientation, it can be used as a material for manufacturing a piezoelectric element whose crystal axes are aligned in the same direction, and the element can be manufactured easily and efficiently.

Further, according to the structure of the invention of claim 2, PbT
When i03 powder is used as a starting material, as the amount of La, O, increases, the grains tend to grow into a cubic shape.
This has the effect that the average particle size can be reliably increased.

[Brief explanation of drawings]

1 to 5 show one embodiment of the present invention. In FIG. 1(a), the starting materials are pbo and Tie. In the case of Laz/5T40x blending ratio x = 0
．． It is an X-ray diffraction diagram at 05 o'clock. In FIG. 1(b), the starting materials are PbO and TiO. In the case of Laz7sTi03 blending ratio x = 0
．． It is an X-ray diffraction diagram at 07:00. In FIG. 1(C), the starting materials are PbO and Tie. In the case of Laz/zTi03 blending ratio x = 0
．． It is an X-ray diffraction diagram at 10 o'clock. FIG. 2(a) is an X-ray diffraction diagram when the starting material is PbTi0:+ and the blending ratio x of Laz/:+TiO3 is 0.05. Figure 2(b) shows that the starting material is P b T i Os.
For E, the blending ratio of Laz/:+TiO3 x = 0
．． It is an X-ray diffraction diagram at 07:00. FIG. 2(C) is an X-ray diffraction diagram when the starting material is PbTiC1+ and the Laz/sT'10s blending ratio x=0.10. Figure 3 shows the L of each orientation degree F of lead titanate produced by combining the starting materials with pbTios or PbO and Tie.
It is a blending ratio dependence characteristic diagram of az/3Ti03. FIG. 4 is a photograph substituted for a drawing showing the particle structure of lead titanate produced using PbO and Tie as starting materials. FIG. 5 shows that the starting material is PbTi0. It is a photograph substituted for a drawing showing the particle structure of lead titanate produced by binding.

Claims (2)

[Claims] 1. Using PbTiO_3 powder as a starting material, a
A PbTiO_3 solid solution characterized by having crystallographic axes oriented in the direction of the axis and the c-axis. 2. Using PbTiO_3 powder as a starting material, PbTiO
Adding La_2O_3 and MnO_2 to _3 at the same time,
P characterized by easy grain growth into a cubic shape by wet mixing in the presence of ethanol and baking.
bMethod for producing TiO_3 solid solution.