Multilayer Piezoelectric Device and Method for Manufacturing the Same

Abstract

A multilayer piezoelectric device including a body having internal electrode layers and piezoelectric ceramic layers alternately stacked. The internal electrode layers contain Cu as a major component, the piezoelectric ceramic layers contain a compound oxide represented by Pb(Ti, Zr)O 3 as a major component, and a metal oxide (Nb 2 O 5 , Sb 2 O 5 , Ta 2 O 5 , or WO 3 ) containing Nb, Sb, Ta, or W, which is at least one of a pentavalent metal element and a hexavalent metal element, is incorporated in the piezoelectric ceramic layers such that the concentration of the metal oxide decreases with distance from the internal electrode layers. Thereby, even in a case where internal electrodes contain Cu as a major component, it is possible to provide a multilayer piezoelectric device which can be obtained by low-temperature firing while ensuring a sufficient piezoelectric constant.

1 . A method for manufacturing a multilayer piezoelectric device, the method comprising:
 alternately stacking internal electrode patterns and piezoelectric ceramic green sheets to form a laminate; and   firing the laminate to form a body in which internal electrode layers and piezoelectric ceramic layers are alternately stacked,   wherein the piezoelectric ceramic green sheets contain a compound oxide represented by Pb(Ti, Zr)O 3  as a major component,   the internal electrode patterns contain a conductive powder containing Cu and at least one of a pentavalent metal element and a hexavalent metal element, and   during firing, the metal element is diffused in the form of a metal oxide from the internal electrode layers into the piezoelectric ceramic layers such that the concentration of the metal oxide decreases with distance from the internal electrode layers.   
     
     
         2 . The method for manufacturing a multilayer piezoelectric device according to  claim 1 , wherein the metal element is at least one element selected from the group consisting of Nb, Sb, Ta, and W. 
     
     
         3 . The method for manufacturing a multilayer piezoelectric device according to  claim 1 , wherein the metal oxide is by any one of Nb 2 O 5 , Sb 2 O 5 , Ta 2 O 5 , and WO 3 . 
     
     
         4 . The method for manufacturing a multilayer piezoelectric device according to  claim 1 , wherein the content of the metal oxide is less than 40.0% by weight on the basis of the total content of the conductive powder and the metal oxide. 
     
     
         5 . The method for manufacturing a multilayer piezoelectric device according to  claim 1 , wherein firing is conducted at a temperature of from about 950° C. to about 1000° C. 
     
     
         6 . The method for manufacturing a multilayer piezoelectric device according to  claim 5 , wherein firing is conducted for about 5 to 10 hours. 
     
     
         7 . The method for manufacturing a multilayer piezoelectric device according to  claim 1 , wherein the firing is conducted in an atmosphere having an oxygen partial pressure between an equilibrium partial oxygen pressure for Pb—PbO and an equilibrium partial oxygen pressure for Cu—CuO.