Piezoelectric Ceramics of Pb(Zr–Ti)O₃ Modified by A¹⁺B⁵⁺O₃ or A³⁺B³⁺O₃

The properties of the solid solutions (Pb 1- x –A x )((Zr y –Ti 1- y ) 1- x –B x )O 3 or (1- x )Pb(Zr y –Ti 1- y )O 3 – x ABO 3 are studied, where A is a mono- or trivalent ion and B a penta- or trivalent ion as follows: A 1+ =K, Na, B 5+ =Sb, Nb, Bi; A 3+ =Bi, La, B 3+ =Fe, Al, Cr. The composition ranges examined are mostly within x <0.2 and 0.4< y <0.7. With the present method of preparation by the solid state reaction, the soluble range lies mostly within about ten mole percent substitution, but in some cases, for example, for the combination of Bi–Fe or Na–Nb, it spreads much wider. The effects of B ion on the falling of the Curie point and on the shift of the boundary between the tetragonal and rhombohedral phases are discussed. The piezoelectric performances of Pb(Zr–Ti)O 3 ceramics are improved by the present modification with ABO 3 ; that is, the dielectric constant increases and the electromechanical coupling coefficient first increases to a broad maximum and then decreases. The coupling coefficient over 0.5 is easily obtained even for less dense ceramics, especially in the case of NaNbO 3 substitution.