Piezoelectric ceramic, method of producing the same, and piezoelectric part

Abstract

A piezoelectric contains comprises a plurality of piezoelectric particles made from a piezoelectric material such as lead titanate zirconate and a dielectric made from a dielectric material, such as a composite perovskite compound, having a higher dielectric constant then the piezoelectric material, the dielectric existing in gaps between the piezoelectric particles. When poling to produce a piezoelectric ceramic, the poling is uniformly performed, and nearly all of the electric field is applied to the piezoelectric particles. Thus, the dispersion of the piezoelectric properties can be reduced, and the piezoelectric properties can be enhanced.

What is claimed is:  
     
         1 . A piezoelectric ceramic body comprising a plurality of piezoelectric material particles and dielectric particles comprising a dielectric material having a higher dielectric constant than said piezoelectric material, the dielectric disposed in gaps between the piezoelectric particles.  
     
     
         2 . A piezoelectric ceramic body according to  claim 1 , wherein the piezoelectric material is at least one member of the group consisting of lead titanate zirconate, lead titanate, lead titanate zirconate containing a composite perovskite compound as a solid solution therein, and lead titanate containing a composite perovskite compound as a solid solution therein.  
     
     
         3 . A piezoelectric ceramic body according to  claim 2 , wherein the dielectric material is at least one member of the group consisting of a composite perovskite compound, a solid solution of a composite perovskite compound and lead titanate, and the combination of a dielectric constant enhancement oxide and a piezoelectric material.  
     
     
         4 . A piezoelectric ceramic body according to  claim 3 , wherein the dielectric powder has a particle size which is not more than about ¼ of the particle size of the piezoelectric powder.  
     
     
         5 . A piezoelectric ceramic body according to  claim 4 , wherein the dielectric powder content does not exceed about 3 weight parts per 100 weight parts of the piezoelectric powder.  
     
     
         6 . A piezoelectric ceramic body according to  claim 5 , wherein the body has an outer surface with an electrode thereon.  
     
     
         7 . A piezoelectric ceramic body according to  claim 1 , wherein the dielectric material is at least one member of the group consisting of a composite perovskite compound, a solid solution of a composite perovskite compound and lead titanate, and the combination of a dielectric constant enhancement oxide and a piezoelectric material.  
     
     
         8 . A piezoelectric ceramic body according to  claim 1 , wherein the dielectric powder has a particle size which is not more than about ¼ of the particle size of the piezoelectric powder.  
     
     
         9 . A piezoelectric ceramic body according to  claim 1 , wherein the dielectric powder content does not exceed about 3 weight parts per 100 weight parts of the piezoelectric powder.  
     
     
         10 . A piezoelectric ceramic body according to  claim 1 , wherein the body has an outer surface with an electrode thereon.  
     
     
         11 . A method of producing a piezoelectric ceramic comprising: 
 providing a body of predetermined shape comprising a mixture of calcined piezoelectric material powder and calcined dielectric material powder, wherein said dielectric material has a higher dielectric constant than said piezoelectric material; and    firing the formed piece, so that a sintered piece as a piezoelectric ceramic is produced.    
     
     
         12 . A method of producing a piezoelectric ceramic according to  claim 11 , further comprising forming said mixture into said predetermined shape.  
     
     
         13 . A method of producing a piezoelectric ceramic according to  claim 12 , further comprising forming said mixture.  
     
     
         14 . A method of producing a piezoelectric ceramic according to  claim 11 , wherein the calcined dielectric material powder has a particle size which is not more than about one fourth of the particle size of the calcined piezoelectric material powder.  
     
     
         15 . A method of producing a piezoelectric ceramic according to  claim 11 , wherein the calcined dielectric material powder is present in an amount of not more than about 3 parts by weight based on 100 parts by weight of the calcined piezoelectric material powder.  
     
     
         16 . A method of producing a piezoelectric ceramic comprising: 
 providing a calcined piezoelectric material powder;    providing a calcined dielectric material powder, wherein said dielectric material has a higher dielectric constant than said piezoelectric material;    mixing the calcined piezoelectric material powder with the calcined dielectric material powder  1 , so that mixed powder is produced;    forming the mixed powder into a predetermined shape, so that a formed piece is produced; and    firing the formed piece, so that a sintered piece as a piezoelectric ceramic is produced.    
     
     
         17 . A method of producing a piezoelectric ceramic according to  claim 16 , wherein the calcined dielectric material powder has a particle size which is not more than about one fourth of the particle size of the calcined piezoelectric material powder.  
     
     
         18 . A method of producing a piezoelectric ceramic according to  claim 17 , wherein the calcined dielectric material powder is mixed with the calcined piezoelectric material powder in an amount not more than about 3 parts by weight based on 100 parts by weight of the calcined piezoelectric material powder.