Solid solutions of Pb1-xSmx (Zr0.55Ti0.45)(1-x/4)O-3 (PSZT) (x = 0.00, 0.03, 0.06 and 0.09) were synthesized by mixed oxide method at high temperature. The formations of single-phase compounds were confirmed by X-ray diffraction studies with tetragonal structure at room temperature. Detailed studies of dielectric properties of PSZT materials were made at various temperatures and frequencies which reveal that the compounds have transition temperature well above the room temperature. The diffusivity (gamma) of the dielectric peaks in the compounds exhibited the values between 1 and 2 where the higher value indicated the greater disorder in the system. The temperature dependence of ac conductivity indicated that the conduction process is due to singly ionized (in ferroelectric region) and doubly ionized (in paraelectric region) oxygen vacancies. (C) 2009 Elsevier B.V. All rights reserved.