Patent ID: 7598659

Claim:
A piezoelectric/electrostrictive device comprising: a piezoelectric/electrostrictive portion made of a piezoelectric ceramic having a composition represented by the following general formula (1): {Li y (Na 1-x K x ) 1-y } a (Nb 1-z Ta z )O 3 (1), in which a=0.90 to 1.2, x=0.2 to 0.8, y=0.02 to 0.2, and z=0.05 to 0.5; and electrodes electrically connected to the piezoelectric/electrostrictive portion; wherein the piezoelectric ceramic is configured to reversibly transit to a tetragonal phase and an orthorhombic phase at a phase transition point as a boundary; wherein the piezoelectric/electrostrictive portion is formed by a polarization treatment performed under conditions wherein a treatment temperature ranges from a first temperature which exceeds the phase transition point of the piezoelectric ceramic to a second temperature which is 50° C. higher than the first temperature; and wherein in the piezoelectric/electrostrictive portion, a mass ratio of a content (T) of tetragonal crystals and a content (R) of orthorhombic crystals at 25° C. is in a range of T:R=2:8 to 10:0.