Piezoelectric element and method of producing the same

Abstract

A piezoelectric element contains a piezoelectric ceramic body having a layered perovskite structure, and has the C axis selected and oriented in the thickness direction. In the piezoelectric ceramic body, line shaped electrodes are formed perpendicular to the C axis selected and oriented. The electrodes exposed at both of the end faces of the piezoelectric ceramic body are covered with conductive materials and insulation materials. The piezoelectric ceramic body is polarized in the opposite directions on both of the sides of electrodes arranged in the width direction. Moreover, external electrodes are formed on the faces where the conductive materials and the insulation materials are formed, whereby two groups of the electrodes are arranged in an interdigital electrode form.

What is claimed is:  
     
         1 . A piezoelectric element comprising a piezoelectric ceramic body having a layered perovskite structure in which at least the C axis of the crystallographic axes is oriented, and which is polarized substantially in the direction perpendicular to the orientation direction of the C axis, and 
 a plurality of electrodes arranged on planes substantially parallel to the polarization direction of the piezoelectric ceramic body in the piezoelectric ceramic body, a first group of the electrodes being adapted to be connected to a first potential and a second group of the electrodes being adapted to be connected to a second potential,    wherein the electrodes are arranged so that the electrodes adapted to be connected to the first potential and the electrodes adapted to be connected to the second potential contain portions which are adjacent to each other.    
     
     
         2 . A piezoelectric element according to  claim 1 , wherein the plurality of electrodes are arranged in an interdigital electrode form.  
     
     
         3 . A piezoelectric element according to  claim 2 , wherein a plurality of electrodes are disposed on a multitude of planes in the orientation direction of the C axis, and electrodes overlapped with each other are connected to the same potential.  
     
     
         4 . A piezoelectric element according to  claim 3 , wherein the piezoelectric ceramic body is polarized in two opposite directions between electrodes overlapped and adapted to be connected to the first potential and electrodes overlapped and adapted to be connected to the second potential.  
     
     
         5 . A piezoelectric element according to  claim 1 , wherein the piezoelectric ceramic body is selected from the group consisting of Na 0.5 Bi 4.6 Ti 4 O 15 , CaBi 4 Ti 4 O 15 , SrBi 4 Ti 4 O 15  and Bi 4 Ti 3 O 12 .  
     
     
         6 . A piezoelectric element according to  claim 1 , wherein a plurality of electrodes are provided on a multitude of planes in the orientation direction of the C axis, and electrodes overlapped with each other are connected to the same potential.  
     
     
         7 . A piezoelectric element according to  claim 6 , wherein the piezoelectric ceramic body is polarized in two opposite directions between electrodes overlapped and adapted to be connected to the first potential and electrodes overlapped and adapted to be connected to the second potential.  
     
     
         8 . A piezoelectric element according to  claim 1 , wherein the piezoelectric ceramic body is polarized in two opposite directions between electrodes adapted to be connected to the first potential and electrodes adapted to be connected to the second potential.  
     
     
         9 . A piezoelectric element according to  claim 1 , wherein the piezoelectric ceramic body is selected from the group consisting of Na 0.5 Bi 4.6 Ti 4 O 15 , CaBi 4 Ti 4 O 15 , SrBi 4 Ti 4 O 15  and Bi 4 Ti 3 O 12 .  
     
     
         10 . A method of producing a piezoelectric element comprising 
 forming a piezoelectric body material having a layered perovskite structure into a green sheet;    printing an electrode paste onto the green sheet at a plurality of positions such that the resulting electrode paste printings are substantially parallel to each other on the green sheet;    laminating a plurality of said green sheets such that the electrode paste printings are interposed between piezoelectric body material, whereby a laminate is formed;    firing the laminate such that the C axes of the piezoelectric body materials are oriented substantially parallel to the lamination direction of the laminate, and    polarizing the fired laminate substantially perpendicular to the orientation direction of the C axes.    
     
     
         11 . A method of producing a piezoelectric element according to  claim 10 , wherein the plurality of green sheets are laminated such that an electrode paste printing on each of at least two green sheets overlap one another in the lamination direction.  
     
     
         12 . A method of producing a piezoelectric element according to  claim 11 , wherein the electrode paste printings are effected in substantially straight lines.  
     
     
         13 . A method of producing a piezoelectric element according to  claim 12 , wherein each electrode paste printing has first and second ends, and including disposing a conductor at said first end and an insulator at said second end.  
     
     
         14 . A method of producing a piezoelectric element according to  claim 13 , wherein said disposing a conductor at said first end and an insulator at said second end is effected such that the first end of one of a pair of adjacent parallel printings is adjacent the second end of the other of the pair of adjacent parallel printings.  
     
     
         15 . A method of producing a piezoelectric element according to  claim 14 , including electrically connecting first ends of printings which overlap one another in the lamination direction to the same potential.