B-Ion Substitution in (Pb-A)(Ti-B)O3 Systems with A=Na1/2Bi1/2 or K1/2Bi1/2 and B=Zr, Fe1/2Nb1/2, Zn1/3Nb2/3, Mg1/3Nb2/3 or Mg1/2W1/2

Phase relation of the systems [Pb_{1- y}(Na_1/2Bi_1/2) _y](Ti_{1- x}Zr _x)O₃ and [Pb_{1- y}(K_1/2Bi_1/2) _y](Ti_{1- x}B _x)O₃ with B=Zr, Fe_1/2Nb_1/2, Zn_1/3Nb_2/3, Mg_1/3Nb_2/3 or Mg_1/2W_1/2 have been investigated. With increasing x and y, T _C decreased and peaks in ɛ-T curves became broader. Phase diagrams of all the systems at room temperature were determined. As the concentration y of Na_1/2Bi_1/2 or K_1/2Bi_1/2 was increased, the tetragonal-to-rhombohedral boundary shifted to smaller x and the tetragonal phase was suppressed within x∼0.1 on the ( K_1/2Bi_1/2) side. Piezoelectric response was examined in ceramic specimens with composition in the vicinity of the boundary in all systems, and a value of 0.18 as K(=C₁/C₀) was found in the [Pb-(K_1/2Bi_1/2)](Ti-Zr)O₃ system.