JPH02224283A - Laminated electrostrictive element - Google Patents

Abstract

PURPOSE:To sinter a title element using a base metal electrode without controlling oxygen concentration by employing as the title element for a ceramics actuator, which mainly includes Ni-containing metal as an internal electrode. CONSTITUTION:There is employed as a title element one that is a laminated electrostriction element for a ceramics actuator and mainly employs Ni- containing metal as an internal electrode. Ni metal has its melting point higher than a sintering temperature of a porcelain without being melted and volatiled during sintering. Additionally, the electrostriction element is preferably a PbTiO3-PbZrO3 piezoelectric porcelain (but, part of Pb is replaced by one or more of Sr, Ba, and Ca, and the amount of the substitution is 20atomic% or above). Hereby, the title element can be sintered in nitrogen using a base metal electrode material as an internal electrode without the need of controlling oxygen concentration in the sintering atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application In recent years, as semiconductor devices and the like have become increasingly integrated, there has been a strong desire for technology to control displacement on the order of microns in the manufacturing process. Actuators that utilize piezoelectric/electrostrictive effects are expected to become central mechanical elements in next-generation micromechatronics. Displacement elements that adjust position have become desirable.

BACKGROUND OF THE INVENTION One of the manufacturing processes of a conventional multilayer piezoelectric element is a process of forming internal electrodes. A screen printing method using paste is generally used as a method for forming the internal electrodes. Paste is a slurry made by dispersing fine metal powder in an organic binder, and is roughly divided into noble metal paste and base metal paste depending on the type of fine metal powder. The former can be fired in the atmosphere, while the latter requires firing in a nitrogen atmosphere.

The laminated piezoelectric element consists of ceramic (oxide) and internal electrode (gold W).
Since A) is manufactured by simultaneously sintering at the sintering temperature of ceramics, the following problems occur. Sintering ceramics in an oxygen atmosphere is essential because sintering them in nitrogen turns them into semiconductors.

Furthermore, when base metal electrodes are used, they are oxidized by sintering in oxygen and lose their electrical conductivity, which is necessary for an electrode.Therefore, various studies have been conducted in recent years to use base metal electrode materials as internal electrodes. For example, this is made possible by strictly controlling the oxygen concentration in the sintering atmosphere.

However, if this method were to be put into practical use, it would be extremely difficult to control the oxygen concentration, leading to an increase in production costs. Furthermore, methods using precious metals have been widely used for some time.

Although it is not necessary to control the sintering atmosphere as compared to base metals, the price of metals is much higher than that of base metals, and the cost of these internal electrodes currently accounts for most of the price of a laminate element.

As described above, there is no conventional technology that can easily produce a laminate at low cost.

Problems to be Solved by the Invention An object of the present invention is to find a ceramic mRW composition that can be sintered using a base metal electrode without controlling the oxygen concentration.

Means to Solve the Problem Conventionally, lead zirconate titanate, etc., have been used as piezoelectric elements, but the internal electrodes of this piezoelectric material laminate include PL,
Precious metals such as Pd and Ag were used. The reason why base metal electrode materials are not used is that porcelain itself becomes a semiconductor when sintered in nitrogen. As a result of intensive study of the above-mentioned drawbacks, the present inventors have developed a multilayer electrostrictive element for ceramic actuators. It is characterized by mainly using Ni-containing metal as the internal electrode, and is also characterized by using a PbTi0s-PbZrOs-based piezoelectric ceramic (however, Pb
is partially substituted with one or more of Sr, Ba, and Ca, and the amount of WtA is 20 at% or more. ) and completed the invention.

The reason why Ni metal is limited to the main component in the present invention is that the sintering temperature of the above-mentioned porcelain is 1200-1350°C, and the melting point of base metals other than Ni is lower than the sintering temperature. This is because there is a risk that it will dissolve or volatilize during freezing. Ni metal has a melting point of about 1450° C., which is higher than the sintering temperature of the porcelain shown in the present invention.Also, metals with high melting points include noble metals, but in this case, the price is very high, leading to an increase in costs. However, the Ni-containing metal referred to in the present invention can be used as long as it forms a solid solution with Ni and has a melting point higher than the sintering temperature. In addition, as long as Ni is the main component, even if it contains noble metals, it can be a part of the present invention because it reduces costs.The composition of the electrostrictive element according to the present invention is basically lead zirconate titanate. However, a portion of the pb contains at least 2 alkaline earth metals.
A ceramic that does not become a semiconductor even in a nitrogen atmosphere was discovered by substituting 0 at%.

Examples Example I P b O, B a COz, ZrO,, T i Oz
Each raw material of (P bl-xB aa+) (Z r*
, ssT ie, *s) Os, and mixed in a ball mill for 10 hours. The resulting mixture
Calcining was performed at 00 to 900°C for 2 hours. Thereafter, it was finely ground again using a ball mill. After drying, a solvent and a binder were added, and a thin film was prepared using doctor play. This Ti
Ni paste was printed and coated on 1e, and each thin film was stacked and thermocompression bonded to form a laminate. Heat this to 1200-1350°C
The sample was sintered in nitrogen for 3 hours. The shape of the sintered porcelain was 1100r with an inter-electrode distance of 100 microns. Electrodes were taken out every other layer from both ends of the sintered IF device and used as external electrodes. Apply voltage to the external electrode, 10kV/
The amount of displacement in cm and the insulation resistance (DC20V) were measured.

The amount of displacement was measured using a potentiometer. An example of the measurement results is shown in Table 1.

Table I By adding , a ceramic composition which does not become a semiconductor even when sintered in nitrogen and has an insulation resistance of 1013 ohm-cm or more has been discovered. This is achieved by adding an alkaline earth metal to lead zirconate titanate, which has been used hitherto for boat fishing. Since sintering in nitrogen has become possible, it has become possible to use Ni metal as the internal electrode without requiring atmosphere control.

Additionally, since no precious metals are used, costs can be significantly reduced.

Patent applicant: Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Scope of Claims] 1) A laminated electrostrictive element for a ceramic actuator, characterized in that a Ni-containing metal is mainly used as an internal electrode. 2) Claim 1, wherein the electrostrictive element is a piezoelectric ceramic based on PbTiO_3-PbZrO_3 (however, a portion of Pb is replaced with one or more of Sr, Ba, and Ca, and the amount of the replacement is 20 at% or more). laminated electrostrictive element