Patent ID: 8414791

Claim:
A piezoelectric/electrostrictive ceramic sintered body having a microstructure in which a matrix phase and an additional material phase having different compositions coexist and the additional material phase is dispersed in the matrix phase, wherein: a residual strain ratio of the additional material phase alone is larger than a residual strain ratio of the matrix phase alone; a composition of the matrix phase and a composition of the additional material phase are selected from a composition range of a composite in which at least one of a Mn compound, containing Mn atoms of 0.001 parts by mole or more and 3 parts by mole or less, and a Ba compound, containing Ba atoms of 0.01 parts by mole or more and 1 part by mole or less, are contained in a compound of 100 parts by mole represented by a general formula {Li y (Na 1-x K x ) 1-y } a (Nb 1-z-w Ta z Sb w )O 3 , where a, x, y, z and w satisfy 0.9≦a≦1.2, 0.2≦x≦0.8, 0.0≦y≦0.2, 0≦z≦0.5 and 0≦w≦0.1, respectively; zero or one kind of element is not common to constituent elements of the matrix phase and constituent elements of the additional material phase in comparison therebetween; wherein the composition of the additional material phase alone is selected so that the residual strain ratio in a long side direction of a rectangular plate polarized in a thickness direction of the additional material phase is 800 ppm or more; and wherein part or all of said at least one Mn compound and Ba compound forms a solid solution with said compound.