The structure and temperature dependence of complex lead perovskite dielectrics were investigated for the system (1 ؊ x)Pb(Yb 1/2 Ta 1/2 )O 3 -xPb(Lu 1/2 Nb 1/2 )O 3 . Superlattice reflections for the compositions 0.8 < x < 1.0 were observed by X-ray diffractometry, and the temperature-composition dielectric-state diagram was determined. In the present study, the disordered middle composition, with 0.2 < x < 0.8, showed a diffuse paraelectric-ferroelectric phase transition, whereas the ordered end compositions, with 0 < x < 0.2 and 0.8 < x < 1.0, revealed successive sharp paraelectric-antiferroelectric and weak antiferroelectric-ferroelectric phase transitions. The dielectric state was confirmed by examining the variation of polarization (P) with electric field (E).

Phase analyses in the solid solution of were conducted by dielectric properties, heat capacity and E - P hysteresis at intervals. Lattice constants and superlattice intensities were analysed by x-ray diffraction, and the temperature - composition phase diagrams were determined. The system was found to form a solid solution of perovskite structure throughout the entire composition range, but the nature of phase transitions changes from ferroelectric - paraelectric for to antiferroelectric - paraelectric for . The transitions of ferroelectric-paraelectric and antiferroelectric - paraelectric for and for , respectively, were diffuse, while those of the ferroelectric - paraelectric and the antiferroelectric - paraelectric for and , respectively, were sharp.