Piezoelectric/electrostrictive ceramics sintered body

A piezoelectric/electrostrictive ceramic sintered body, which has 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 a Mn compound containing Mn atoms of 0 parts by mole or more and 3 parts by mole or less and a Ba compound containing Ba atoms of 0 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 {Liy(Na1-xKx)1-y}a(Nb1-z-wTazSbw)O3, 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;
• and
• 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.