Method of producing a piezoelectric/electrostrictive device and piezoelectric/electrostrictive element

Abstract

A piezoelectric/electrostrictive device is provided, including a pair of mutually confronting thin plate portions, a fixing portion for supporting the pair of thin plate portions, movable portions provided at tip end portions of the pair of thin plate portions and having mutually confronting end surfaces, and piezoelectric/electrostrictive elements disposed on respective thin plate portions. At least both side surfaces of the thin plate portions and the piezoelectric/electrostrictive elements are covered with coating films made of a material with a low thermal expansion coefficient.

1 . A method of producing a piezoelectric/electrostrictive device comprising a pair of mutually confronting thin plate portions, and a fixing portion supporting said pair of thin plate portions, wherein movable portions are provided at tip end portions of said pair of thin plate portions, said movable portions have mutually confronting end surfaces, and one or more piezoelectric/electrostrictive elements are disposed on at least one of said pair of thin plate portions, 
 wherein said method comprises steps of forming said one or more piezoelectric/electrostrictive elements on said at least one of said pair of thin plate portions, then covering at least both side surfaces of said thin plate portions and said one or more piezoelectric/electrostrictive elements with coating films made of a low thermal expansion coefficient material by a film formation method.    
   
   
       2 . A method of producing a piezoelectric/electrostrictive device according to  claim 1 , wherein said film formation method is a method selected from the group consisting of sticking of a filmy plate, coating, dipping, sputtering, CVD, and laser ablation.  
   
   
       3 . A method of producing a piezoelectric/electrostrictive element according to  claim 1 , wherein said method further comprises covering at least a pair of side surfaces parallel to a displacing direction with coating films made of substantially SiO 2  only and each having a thickness of 0.1 μm or greater with a film formation method.  
   
   
       4 . A method of producing a piezoelectric/electrostrictive element according to  claim 3 , wherein said film formation method is a coating method or a dipping method using a polysilazane.  
   
   
       5 . A method of producing a piezoelectric/electrostrictive device comprising a thin plate portion and a fixing portion supporting said thin plate portion and formed with a cavity inside, wherein one or more piezoelectric/electrostrictive elements are disposed on said thin plate portion in a position corresponding to the cavity of said fixing portion, wherein said method comprises steps of: 
 preparing a joined body by joining a thin plate that becomes said thin plate portion later, and a thick plate that comprises at least one layer and becomes said fixing portion later, through diffusion joining; and    forming said one or more piezoelectric/electrostrictive elements on said thin plate of said joined body.    
   
   
       6 . A method of producing a piezoelectric/electrostrictive device comprising a pair of mutually confronting thin plate portions and a fixing portion supporting said pair of thin plate portions, wherein one or more piezoelectric/electrostrictive elements are disposed on at least one of said pair of thin plate portions, wherein said method comprises steps of: 
 preparing a joined body by joining thin plates that become said thin plate portions later, and one or more thin plates or thick plates that become said fixing portion later, through diffusion joining;    disposing said one or more piezoelectric/electrostrictive elements on at least one of said thin plates of said joined body to prepare an original piezoelectric/electrostrictive device; and    cutting said original piezoelectric/electrostrictive device to obtain individual piezoelectric/electrostrictive devices.    
   
   
       7 . A method of producing a piezoelectric/electrostrictive device comprising a pair of mutually confronting thin plate portions, and a fixing portion supporting said pair of thin plate portions, wherein movable portions are provided at tip end portions of said pair of thin plate portions, said movable portions have mutually confronting end surfaces, and one or more piezoelectric/electrostrictive elements are disposed on at least one of said pair of thin plate portions, wherein said method comprises steps of: 
 preparing intermediate joined bodies each by joining a thin plate that becomes said thin plate portion later, and one or more thin plates or thick plates that become said movable portion and part of said fixing portion later, through diffusion joining;    preparing a joined body by joining said intermediate joined bodies and one or more thin plates or thick plates that become said fixing portion later, through diffusion joining;    disposing said one or more piezoelectric/electrostrictive elements on at least one of said thin plates of said joined body to prepare an original piezoelectric/electrostrictive device; and    cutting said original piezoelectric/electrostrictive device to obtain individual piezoelectric/electrostrictive devices.    
   
   
       8 . A method of producing a piezoelectric/electrostrictive device according to  claim 5 , wherein a 0.2% proof stress at 800° C. of said thin plate or thick plate is 75 MPa or greater.  
   
   
       9 . A method of producing a piezoelectric/electrostrictive device according to  claim 5 , wherein said diffusion joining is a joining method in which a member to be joined is placed between two pressure dies and pressed at a predetermined temperature, and in which said member to be joined is pressed in the state where pressure plates made of the same material as that of said member to be joined and applied with solid lubricant are interposed between said pressure dies and said member to be joined.  
   
   
       10 . A method of producing a piezoelectric/electrostrictive device according to  claim 9 , wherein said solid lubricant contains at least hexagonal boron nitride.  
   
   
       11 . A method of producing a piezoelectric/electrostrictive device according to  claim 5 , wherein said diffusion joining is a joining method in which a member to be joined is placed between two pressure dies and pressed at a predetermined temperature, and in which said member to be joined is pressed in the state where ceramic pressure plates having a thermal expansion coefficient that is within a range of ±30% relative to a thermal expansion coefficient of said member to be joined, are interposed between said pressure dies and said member to be joined.  
   
   
       12 . A method of producing a piezoelectric/electrostrictive device according to  claim 11 , wherein said ceramic pressure plates are made of calcium oxide or magnesium oxide of 80% or more purity.  
   
   
       13 . A method of producing a piezoelectric/electrostrictive device according to  claim 5 , wherein said thin plate or thick plate that becomes at least part of said fixing portion later, is formed with a window portion in advance.