Perovskite oxide, process for producing the perovskite oxide, and piezoelectric device

A piezoelectric oxide having a composition expressed by a compositional formula,

• (Ba, Bi, A)(Ti, Fe, M)O3,
• where each of A and M represents one or more metal elements other than Pb;
• Ba, Bi, and A are A-site elements, Ti, Fe, and M are B-site elements, Ba, Bi, Ti, Fe and O respectively represent barium, bismuth, titanium, iron, and oxygen, the one or more B-site elements represented by M are elements other than Ti and Fe when the one or more A-site elements represented by A are Ba and/or Bi, the one or more A-site elements represented by A are elements other than Ba and Bi when the one or more B-site elements represented by M are Ti and/or Fe, and the ratio of each of the total molar amount of the A-site elements and the total molar amount of the B-site elements to the molar amount of oxygen may deviate from 1:3 within a range in which the composition expressed by the compositional formula (Ba, Bi, A)(Ti, Fe, M)O3 can form a perovskite structure;
• the composition of the compound (Ba, Bi, A)(Ti, Fe, M)O3 is determined so as to satisfy the conditions (1) and (2),
• 0.98≦TF(P)≦1.02, and (1)
• TF(BiFeO3)<TF(AMO3)<TF(BaTiO3), (2)
• where TF(P) is a tolerance factor of the piezoelectric oxide expressed by the compositional formula (Ba, Bi, A)(Ti, Fe, M)O3, TF(BaTiO3) is a tolerance factor of a compound expressed by a compositional formula BaTiO3, TF(BiFeO3) is a tolerance factor of a compound expressed by a compositional formula BiFeO3, and TF(AMO3) is a tolerance factor of a compound expressed by a compositional formula AMO3.