JPH0556031B2 - - Google Patents

Abstract

PURPOSE:To form a sintered body, a shrinkage factor of which at the time of sintering with a piezoelectric layer section coincides and which is not cracked and broken, by containing a silver component into a protective layer section. CONSTITUTION:A piezoelectric material is formed in such a manner that proper quantities of lead oxide, nickel oxide, niobium oxide, zirconium oxide and titanium oxide are mixed and baked respectively and crushed. Silver powder is added to the powder of the piezoelectric material shaped, thus forming a ceramic green sheet. Metallic conductive paste to which silver powder as an internal electrode and palladium powder are added is printed onto a green sheet to which silver powder is not added. Piezoelectric layer sections 1a and 1b are shaped by laminating approximately one hundred layers of the green sheets, to which the internal electrode layers are formed and silver is not added, in the constitution of laminating, the green sheets in silver loading to which the internal electrode layers are not shaped are laminated respectively in fifteen layers, thirty layers and fifteen layers, and the green sheets are employed as 2a, 2c, 2b of a protective layer section 2. The green sheets are laminated, and thermally pressed. The thermally pressed green sheets are shifted into a sintering furnace, and sintered.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention comprises a protective layer portion made of laminated green sheets made of a piezoelectric material whose main component is an oxide of a metal such as lead, zirconium, or titanium; The present invention relates to a laminated piezoelectric element formed by sintering a laminate including a piezoelectric layer portion in which sheets each having an internal electrode layer as a main component formed on the green sheet are laminated.

[Conventional technology]

As shown in Figures 1 and 2, a laminated piezoelectric element consists of internal electrodes made of a conductive paste mainly composed of silver on a green sheet of piezoelectric material mainly composed of metal oxides such as lead, zirconium, and titanium. Piezoelectric layer parts 1, 1 made by laminating a large number of sheets forming layer 3
a, 1b, and protective layer parts 2a, 2b which are laminated with a large number of green sheets made of piezoelectric material that do not form the internal electrode layers. Piezoelectric layer part 1
When a voltage is applied, it stretches in the direction of the electric field due to the inverse piezoelectric phenomenon, and returns to its original position when the voltage is removed. This phenomenon is used to convert electrical energy into mechanical energy through expansion and contraction motion. It is used as a so-called conversion element. The protective layer parts 2a and 2b form a soldering part 5 for applying a voltage, have a transmission function to the receiving side to take out the expansion and contraction movement of the element (protective layers 2a and 2b), or have a function of controlling the length of the element. When it is quite long, it has an extremely important function such as a function to connect the piezoelectric layer parts 1a and 1b (protective layer part 2c in the middle of the element).

Conventionally, the ceramic layer 8 of the piezoelectric layer section 1 and the ceramic layer 9 of the protective layer sections 2a and 2b are laminated green sheets made of a piezoelectric material whose main component is an oxide of a metal such as lead, zirconium, or titanium. It was formed from the body. However, the piezoelectric layer section 1 is laminated with a large number of green sheets in which an internal electrode layer 3 made of a conductive paste containing silver as a main component is formed on the ceramic layer 8 of the piezoelectric layer section 1.

[Problem that the invention seeks to solve]

When such a piezoelectric layer part 1 is sintered under the same conditions as a protective layer part 2 without an internal electrode layer as the same laminate as shown in FIGS. 1 and 2, in the piezoelectric layer part 1, the internal electrode layer 3 Due to the diffusion of silver, the shrinkage rate of the piezoelectric layer part 1 during sintering becomes larger than that of the protective layer part 2, and the state after sintering is that the protective layer part 2 and the piezoelectric layer part 1 are Cracks and fractures occurred at the interface. Furthermore, even if no cracks or fractures occur, the large difference in shrinkage rate during sintering remains as internal stress, causing cracks to occur when the element is driven, resulting in a significant deterioration in quality.

[Means for solving problems]

The laminated piezoelectric element of the present invention includes lead, zirconium,
A protective layer section in which a green sheet made of a piezoelectric material whose main component is an oxide of a metal such as titanium is laminated, and a piezoelectric layer section in which a sheet in which an internal electrode layer mainly composed of silver is formed on the green sheet is laminated. A laminated piezoelectric element formed by sintering a laminate consisting of the following, characterized in that the piezoelectric material constituting the green sheet of the protective layer portion contains a silver component.

[Effect]

According to this method, the difference in shrinkage rate during sintering between the piezoelectric layer portion and the protective layer portion, which is the drawback of the conventional method as described above, is not observed, and cracks and cracks in the element are not likely to occur. Based on numerous experimental results, the appropriate amount of silver to be contained in the protective layer is 5wt% to 0.1wt% based on the ceramic piezoelectric material. If it exceeds this range, the shrinkage ratios may not match, and if it exceeds this range, the electrical properties, such as the electrical insulation resistance value, will decrease, which will affect the performance.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. For drawings, the above-mentioned FIGS. 1 and 2 are used.

The piezoelectric material used in this example was made by mixing appropriate amounts of lead oxide, nickel oxide, niobium oxide, zirconium oxide, and titanium oxide, and then heating it at about 900°C to about 40%
It is produced by firing for a period of time and then pulverizing. The composition of the piezoelectric material is Pb{Ni _1/2 Nb _2/3 ) _0.5 as the final chemical formula.
The raw materials are mixed in a distribution ratio so that Zr _0.35 Ti _0.15 }O ₃ is obtained. The weight ratio of the silver powder to the powder of the piezoelectric material produced in this way is 0, 0.1, 0.5,
They are added to the piezoelectric powder in amounts of 1, 5, and 10 wt%, respectively, and mixed thoroughly. A binder made of an organic polymer and a vehicle are respectively added to this mixed powder and mixed thoroughly, and then a ceramic green sheet of about 120 μm is produced by a slip cast film forming method. A metal conductive paste that will serve as internal electrodes is printed on the green sheet, which does not contain silver powder (0wt%). The metal conductive paste contains silver powder and palladium powder at a weight ratio of 70,
After mixing at 30 wt%, an organic vehicle such as an organic solvent is added thereto and thoroughly kneaded to produce the product.

A green sheet with no added silver powder formed by the internal electrode layer and a green sheet with silver powder added at the weight ratio mentioned above (inner electrodes are not formed on this) so that they have the same shape. Cut many pieces,
Laminate each sheet. The laminated structure is the second
I made it look like the figure. In other words, the silver-free green sheet on which the internal electrode layer is formed is approximately
The piezoelectric layer parts 1a and 1b are obtained by laminating 100 layers, and 15, 30, and 15 green sheets with the above-mentioned silver addition amount, on which no internal electrode layer is formed, are laminated, respectively, and these are formed into the protective layer shown in FIG. Part 2 2a, 2
c, 2b. After laminating, they are hot pressed at a temperature of 120°C and a pressure of 300Kg/cm ² . The press-formed body thus formed is placed in a constant temperature bath at a temperature of about 400°C to burn off the organic matter contained in the press-formed body. Next, it is transferred to a sintering furnace, the temperature is gradually raised to about 1200°C, and sintered for about 2 hours. The sintered body was cut with a cutter, and the effectiveness was determined by visually observing whether or not cracks or cracks had occurred from a cross-sectional view as shown in Figure 2. As a result, the amount of silver added to the protective layer portions 2a, 2b, and 2c is
At 0wt%, that is, when no silver powder was added, cracks and cracks were observed at the interface between the protective layer part 2 and the piezoelectric layer part 1, but when silver powder was added, no tortoise lines and cracks were observed. Not observed.

Next, as a result of measuring the electrical characteristics of the device, it was found that when the amount of silver powder added was 10 wt%, the electrical insulation resistance value became small, resulting in a result that could not be used for practical use.
This is probably because the amount of silver powder increased and the electrical conductivity of the ceramic layer increased. In the case of other amounts of silver added, there were no problems with the properties.

Therefore, the effective amount of silver added is:
For the piezoelectric material used in this example, it was found that the appropriate amount was 0.1 wt% or more and less than 10 wt%.

In this example, one type of piezoelectric material,
In addition, although we have only described the element shape shown in Figure 2, there are other piezoelectric materials whose main components are oxides of metals such as lead, zirconium, and titanium, and other element shapes, such as the one shown in Figure 1. In this case, the same results as in this example were obtained, and the effects of the present invention were similarly recognized.

〔Effect of the invention〕

As explained above, the present invention has the effect that by containing a silver component in the protective layer portion, the shrinkage rate during sintering matches that of the piezoelectric layer portion, and a sintered body that is free from cracks and cracks can be formed. There is.

[Brief explanation of drawings]

FIGS. 1 and 2 are longitudinal cross-sectional views of an embodiment of the laminated piezoelectric element of the present invention. 1, 1a, 1b... piezoelectric layer section, 2a, 2b...
Protective layer portion at the end of the element, 2c... Protective layer portion in the middle of the element, 3... Internal electrode layer, 4... External electrode layer, 5...
...Soldering part, 6...Electric insulating layer part, 7...Lead wire, 8...Ceramic layer of piezoelectric layer part, 9...Ceramic layer of protective layer part.

Claims (1)

[Scope of Claims] 1. A protective layer section in which a green sheet made of a piezoelectric material whose main component is an oxide of a metal such as lead, zirconium, or titanium is laminated, and an internal electrode layer whose main component is silver is combined with the green sheet. In a laminated piezoelectric element formed by sintering a laminate consisting of a piezoelectric layer portion in which sheets formed above are laminated, the piezoelectric material constituting the green sheet of the protective layer portion may contain a silver component. Features a multilayer piezoelectric element.