The PZT is modified by the introduction of doping agents in A-sites and/or B-sites of perovskite structure [1]. The principal role of dopants is generally improving the properties of these materials for their adaptation to specific applications, which is the purpose of this study. Our choice fell on the mixed oxide: acceptor and donor. Five compositions with varying dopants percentage were prepared by the conventional method of thermal synthesis of mixed-oxides. Pb_1-0.04Sm_0.02Nd_0.02[(Zr_0.55,Ti_0.45)_1-2x,x(Y_2/3,Mo_1/3),x(Y_2/3,Ni_1/3)]O₃ such that (x = 0.01, 0.03, 0.05, 0.07 and 0.1), are studied. All the samples were being sintered at a temperature ranging from 1100°C to 1180°C after being compacted in circular discs. The detailed structure was carried out for sintered specimens. The results of X-ray diffraction showed that all the ceramics specimens have a perovskite phase. The phase structure of Pb_1-0.04Sm_0.02Nd_0.02[(Zr_0.55,Ti_0.45)_1-2x, x(Y_2/3,Mo_1/3),x(Y_2/3,Ni_1/3)]O₃ ceramics was transformed from the tetragonal to the rhombohedral, with an increase in the ratio of Zr/Ti in system. The scanning Electron Microscopy (SEM) showed an increase of the mean grain size when the sintering temperature was increased. The lattice parameter measurements showed that tetragonal and rhombohedral unit cells of the phases depend on the sintering temperature.