JPH0442352B2 - - 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 art] In recent years, so-called voltage-driven piezoelectric displacement elements (hereinafter referred to as displacement elements) have been developed as a new driving source to replace electromagnetic systems, which convert electrical energy into mechanical energy by utilizing the electrostrictive effect of piezoelectric ceramics. ) has been put into practical use in relays, switches, minute position control devices, etc.
Progress has been made in many directions. As shown in FIG. 1, this type of displacement element is known to have a bimorph structure, for example, as shown in FIG. There is. When a DC or AC voltage is applied to this displacement element, the mechanical displacement 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 for it to be as large as possible in terms of its function as a displacement element, and therefore piezoelectric ceramic compositions that have a greater electrostrictive effect are advantageous. It is said that Conventionally, piezoelectric ceramic compositions that meet this purpose include Pb(Ni _1/3 Nb _2/3 )O ₃ −PbZrO ₃ −, which has a relatively large piezoelectric constant d ₃₁ .
There are three-component types such as 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 can provide larger mechanical displacements. [Object of the Invention] The present invention fully satisfies these demands, and provides a piezoelectric ceramic that has a large electrostrictive effect due to voltage application, which results in large mechanical displacement, and which can be applied to a wide range of applications as a displacement element. The purpose is to provide a composition. [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 (Sb _1/2 Nb _1/2 ) _B Zr _C Ti _D ] Indicated by O ₃ (A+B+C+D=1) 0.300≦A≦0.550 0.002≦B≦0.050 0.120 To the basic composition satisfying ≦C≦0.290 0.280≦D≦0.408, 0.01 to 0.5% by weight of one selected from oxides of rare earth elements and 0.01 to 0.5% by weight of Cc ₂ O ₃ are added as subcomponents. further comprising an oxide of the rare earth element.
It is characterized by being La ₂ O ₃ , CeO ₂ , Nd ₂ O ₃ , Sm ₂ O ₃ , and Dy 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 , 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, an appropriate amount of an organic binder was added to the powder obtained by pulverization using a ball mill, and the resulting powder was granulated, followed by pressure molding at a pressure of 1 ton/cm ² and calcined at a temperature of 1200 to 1250° C. for several hours. The obtained sintered body is cut into a predetermined shape, polished, provided with electrodes, and heated in silicone oil at a temperature of 60~60℃.
A DC electric field of 35 to 50 kV/cm was applied for 30 minutes at 100°C to perform polarization treatment and piezoelectrically activate it. Next, after determining the various piezoelectric constants using a prescribed 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 and 2 mm in width. , 1mm thick,
A length of 35 mm, width of 10 mm and thickness of 0.15 mm was obtained. A DC voltage of 500 V was applied to the piezoelectric element of these two shapes in the same direction as the polarization direction, and the amount of electrical strain (shrinkage strain) generated at that time was measured (evaluated by Δ/value (Δ...shrinkage strain). For the piezoelectric element of one shape, a bimorph-type displacement element as shown in Fig. 1 was created by sandwiching a metal elastic plate from both sides, and a DC voltage of 30 V was applied to this. Then, the mechanical displacement (the displacement corresponding to dS ₁ in FIG. 1) generated at the tip with one end fixed and the other end free was measured.

【table】

【table】

〔Effect of the invention〕

In this way, the present invention provides Pb [(Ni _1/3 Nb _2/3 ) _A (Sb _1/2
Nb _1/2 ) _B Zr _C Ti _D ]O ₃ as the basic composition, A, B, C,
D is set within an appropriate range, and one type selected from oxides of rare earth elements and Co ₂ O ₃ are used as subcomponents.
It simultaneously contains a moderate amount of
In particular, due to the synergistic effect of the Pb (Sb _1/2 Nb _1/2 ) O ₃ component in the basic composition and the subcomponents, a larger amount of electrical strain and mechanical displacement that could not be achieved with conventional compositions was achieved. It is. Furthermore, 0.300>A, A>0.550, B>0.050, 0.120>
1 selected from basic compositions consisting of C, C>0.290, 0.280>D, D>0.408 and oxides of rare earth elements
In compositions in which the amount of seeds and Co ₂ O ₃ added is more than 0.5% by weight, the amount of electrostriction and mechanical displacement decrease,
It is not preferable as the intended displacement element, and
0.002>B and one type of rare earth element oxide
Compositions in which the amount of Co ₂ O ₃ added was less than 0.01% by weight 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 the The improvement effect has been confirmed, and therefore it is fully applicable to, for example, a laminated piezoelectric displacement element. 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 (Sb _1/2 Nb _1/2 ) _B Zr _C
Ti _D ]O ₃ (where A+B+C+D=1) 0.300≦A≦0.550 0.002≦B≦0.050 0.120≦C≦0.290 0.280≦D≦0.408, and oxides of rare earth elements as subcomponents A piezoelectric ceramic composition comprising 0.01 to 0.5% by weight of one selected from the following and 0.01 to 0.5% by weight of Co ₂ O ₃ . 2 The rare earth element oxide is La ₂ O ₃ , CeO ₂ ,
The piezoelectric ceramic composition according to claim 1, characterized in that it is Nd ₂ O ₃ , Sm ₂ O ₃ , and Dy ₂ O ₃ .