Finite-temperature properties of disordered and ordered Pb(Sc0.5Nb0.5)O-3 alloys

A first-principles-derived approach is used to study the properties of rock salt-ordered and disordered Pb(Sc0.5Nb0.5)O-3 (PSN) alloys. The paraelectri c-to-ferroelectric transition temperature T-c is strongly dependent on the atomic configuration, while the piezoelectric response versus T/T-c is near ly independent of the chemical order. Our calculations are consistent with the experimental finding of Chu [J. Appl. Phys. 77, 1671 (1995)] that, at T =T-c, ordered PSN undergoes a normal ferroelectric transition, while disord ered PSN transforms from a relaxor state to a ferroelectric state. (C) 2000 American Institute of Physics. [S0003-6951(00)02148-3].