JPS6358787B2 - - 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 in which piezoelectric ceramic plates 2 and 2', each having electrodes sandwiched between them, are bonded to a metal elastic plate 1, as shown in FIG. ing. When a DC or AC voltage is applied to this displacement element, a mechanical displacement dS ₁ or dS ₂ occurs due to an electrostrictive effect (in this case, a piezoelectric transverse effect). Although this mechanical displacement depends on the application and the mechanism when installed, it is generally desirable that it be as large as possible in terms of its function as a displacement element.
Therefore, piezoelectric ceramic compositions having greater electrostrictive effects are considered advantageous. 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 can provide larger mechanical displacements. [Objective of the Invention] The present invention satisfactorily satisfies such 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 (Zn _1/3 Nb _2/3 ) _B (Y _1/2 Nb _1/2 ) _C Zr
_D
Ti _E ]O ₃ (where A+B+C+D+E=
1) For the basic composition satisfying 0.300≦A≦0.550 0.005≦B≦0.100 0.002≦C≦0.040 0.050≦D≦0.287 0.260≦E≦0.406, one type selected from oxides of rare earth elements is added as a subcomponent. It is characterized by containing 0.01 to 0.5% by weight and 0.01 to 0.5% by weight of Co ₂ O ₃ , and further containing 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 , ZnO, Y 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
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, further polishing and processing were performed to create rectangular piezoelectric elements of two shapes: 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.

【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 (Y _1/2 Nb _1/2 ) _C Zr _D Ti _E ]O ₃ as the basic composition,
Set A, B, C, D, and E to appropriate ranges,
In addition, it contains one selected from rare earth element oxides and Co ₂ O ₃ as subcomponents in an appropriate range, and in particular, it contains Pb in the basic composition.
[(Zn _1/3 Nb _2/3 ) O ₃ , Pb (Y _1/2 Nb _1/2 ) O ₃ , the synergistic effect of the components and subcomponents allows for greater electrostriction that could not be achieved with conventional compositions. amount, mechanical displacement is what is realized. In addition, 0.300>A, A>0.550, B
＞0.100, C＞0.040, 0.050＞D, D＞0.287,
Basic compositions consisting of 0.260>E and E>0.406 and compositions containing one selected from rare earth element oxides and Co ₂ O ₃ in an amount of more than 0.5% by weight each have lower electrostriction and mechanical The target displacement decreases, making it undesirable for the intended displacement element;
B, 0.002>C and rare earth element oxides and a composition in which the amount of Co ₂ O ₃ added is less than 0.01% by weight will not produce a significant improvement effect, so it is not within the scope of the present invention. Excluded. 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 have been explained with particular reference to the bimorph type piezoelectric displacement element, but the piezoelectric longitudinal effect was also investigated using the same composition. Its improvement effect 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 the drawing]

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 (Y _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≦0.040 0.050≦D≦0.287 0.260≦E≦0.406 For a satisfactory basic composition, A piezoelectric ceramic composition comprising 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 Co ₂ O ₃ as components. 2 The rare earth element oxide is La ₂ O ₃ , CeO ₂ ,
The piezoelectric ceramic composition according to claim 1, characterized in that the composition is Nd ₂ O ₃ , Sm ₂ O ₃ , and Dy ₂ O ₃ .