JPH052624B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a piezoelectric ceramic composition, and more particularly to a piezoelectric ceramic composition suitable for a voltage-driven piezoelectric displacement element that requires large mechanical displacement by voltage application. [Prior technology] In recent years, as a new type of drive source to replace the electromagnetic type,
The practical application of so-called voltage-driven piezoelectric displacement elements (hereinafter referred to as displacement elements), which utilize the electrostrictive effect of piezoelectric ceramics to convert electrical energy into mechanical energy, has been applied to relays, switches, minute position control devices, etc.
Progress is being made on the other side. As an example of this type of displacement element, as shown in FIG. 1, a bimorph structure is known in which piezoelectric ceramic plates 2 and 2' provided with electrodes are attached to a metal elastic plate 1 so as to sandwich them from both sides. It is being When a DC or AC voltage is applied to this displacement element, mechanical displacement occurs due to the electrostrictive effect (in this case, the piezoelectric transverse effect).
dS ₁ or dS ₂ occurs. Although this mechanical displacement depends on the application and the mechanism in which it is mounted, it is generally desirable that the mechanical displacement be as large as possible in terms of its function as a displacement element, and therefore a piezoelectric ceramic composition having a larger electrostrictive effect is advantageous. has been done. Conventionally, piezoelectric ceramic compositions that meet this purpose include, for example, Pb(Ni _1/3 Nb _2/3 )O ₃ −, which has a relatively large piezoelectric constant d ₃₁ .
There are three-component systems such as PbZrO ₃ -PbTiO ₃ . However, the mechanical displacement of conventional compositions was not necessarily sufficient, and their use as displacement elements was limited to an extremely narrow range. Therefore, there has been a desire for a piezoelectric ceramic material that can be used as a displacement element in a wide range of applications and that can provide larger mechanical displacements. [Objective of the Invention] The present invention satisfactorily satisfies such demands, and provides a piezoelectric ceramic composition that has a large electrostrictive effect due to voltage application, resulting in large mechanical displacement, and can be applied to a wide range of applications as a displacement element. The purpose is to provide something. [Structure of the Invention] That is, the piezoelectric ceramic composition of the present invention has the general formula Pb [(Ni _1/3 Nb _2/3 ) _A (Zn _1/2 Nb _2/3 ) _B (Sb _1/2 Nb _1/2 ) _C
Zr _D Ti _E ]O ₃ (A+B+C+D+E=1) 0.300≦A≦0.550 0.005≦B≦0.100 0.002≦C≦0.050 0.070≦D≦0.288 0.230≦E≦0.405 Substitute for a satisfied basic composition NiO as a component,
It is characterized by containing 0.02 to 1% by weight of one selected from Fe ₂ O ₃ and Bi ₂ O ₃ . Examples of the present invention will be described in detail below while comparing with reference examples. [Example] PbO with a chemical purity of 99% or more as a starting material,
NiO, Nb ₂ O ₅ , ZnO, Sb ₂ O ₃ , ZrO ₂ , TiO ₂ and predetermined subcomponents were selected and precisely weighed to give the compositions shown in Table 1. Next, these raw materials were mixed in a ball mill, dried, and pre-calcined at 850°C. Next, after adding an appropriate amount of organic binder to the powder obtained by crushing with a ball mill and granulating it,
It was press-molded at a pressure of 1 ton/cm ² and fired at a temperature of 1200 to 1250°C for several hours. After cutting and polishing the obtained sintered body into a predetermined shape, electrodes are attached and heated in silicone oil at a temperature of 60 to 100°C in a DC electric field of 35 to 35°C.
A voltage of 50 kV/cm was applied for 30 minutes to perform polarization treatment and piezoelectrically activate it. Next, after determining the various piezoelectric constants using a predetermined measurement method, in order to confirm the actual effect, a further polishing process was performed to obtain two types of rectangular piezoelectric elements: 10 mm in length, 2 mm in width, and 2 mm in width. The thickness was 1 mm, the length was 35 mm, the width was 10 mm, and the thickness was 0.15 mm. Of these two types of piezoelectric elements, the shape
Apply a DC voltage of 500V in the same direction as the polarization direction,
The amount of electrical strain (shrinkage strain) generated at that time is measured and Δ
/value (Δ...shrinkage amount, element length). On the other hand, regarding the shape of the piezoelectric element, a bimorph type displacement element as shown in Fig. 1 was created by sandwiching a metal elastic plate from both sides. The mechanical displacement (the displacement corresponding to dS ₁ in FIG. 1) generated at the tip in the free end state was measured.

【table】

【table】

〔Effect of the invention〕

In this way, the present invention provides Pb[Ni _1/3 Nb _2/3 ) _A (Zn _1/3 Nb _2/3 ) _B (Sb _1/2 Nb _1/2 ) _C Zr _D
The basic composition is Ti _E ] O ₃ , and each of A, B, C, D, and E is set within an appropriate range, and as subcomponents.
It contains one of NiO, Fe ₂ O ₃ and Bi ₂ O ₃ in an appropriate range, and especially Pb in the basic composition.
Due to the synergistic effect with the (Zn _1/3 Nb _2/3 )O ₃ , Pb (Sb _1/2 Nb _1/2 ) components and subcomponents, a larger amount of electrostriction and mechanical Displacement has been realized. In addition, in the present invention, the subcomponents NiO, Fe ₂
Even if two or more of O ₃ and Bi ₂ O ₃ are added, the same effect can be obtained as long as the total added content is in the range of 0.02 to 1% by weight. In addition, 0.300>A, A>0.550, B>0.100, C>
0.050, 0.070＞D, D＞0.288, 0.230＞E, E＞
A basic composition consisting of 0.405 and a composition containing more than 1 wt. >B, 0.002>C
Compositions containing less than 0.02% by weight of one of the selected subcomponents were excluded from the scope of the present invention because no significant improvement effect was observed. The piezoelectric ceramic composition of the present invention can be expected to be applied to the following uses. (1) Since it generates a large mechanical displacement, it can be made smaller, lighter, and driven at lower voltages, and can be applied to new fields of displacement elements suited to the energy-saving era. (2) It can be applied to displacement elements that require large mechanical displacements at relatively low voltages. (3) It can be applied to displacement elements that require large mechanical displacements by adopting a one-sided drive method (applying only a DC voltage in the same direction as the polarization direction of the piezoelectric element). In this case, the magnitude of the applied voltage can be freely selected depending on the application. (4) Since it has a relatively high piezoelectric constant (for example, piezoelectric d constant), it can be applied to various piezoelectric products that require a high piezoelectric constant. In the examples of the present invention, the amount of electrical strain and mechanical displacement associated with the piezoelectric transverse effect were explained with particular reference to the bimorph type piezoelectric displacement element, but the piezoelectric longitudinal effect was also investigated using the same composition and its improvement was carried out. Its effectiveness has been confirmed, and therefore it is fully applicable to, for example, laminated piezoelectric displacement elements. As described in detail above, the piezoelectric ceramic composition of the present invention is suitable for displacement elements that can be used in a wide range of applications, and is of great industrial value.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a bimorph type piezoelectric displacement element, and FIGS. 2a to 2d are graphs showing an example of the effect of the piezoelectric ceramic composition of the present invention on the characteristics of the displacement element. 1... Metal elastic plate, 2, 2'... Piezoelectric ceramic plate.

Claims (1)

[Claims] 1 General formula Pb [(Ni _1/3 Nb _2/3 ) _A (Zn _1/3 Nb _2/3 ) _B (Sb _1/2 Nb _1/2 )
_C
Zr _D Ti _E ]O ₃ (A+B+C+D+E=1) 0.300≦A≦0.550 0.005≦B≦0.100 0.002≦C≦0.050 0.070≦D≦0.288 0.230≦E≦0.405 For a satisfactory basic composition, NiO as a component,
A piezoelectric ceramic composition comprising 0.02 to 1% by weight of one selected from Fe ₂ O ₃ and Bi ₂ O ₃ .