Global and secondary ferroelectric minima in ordered Pb(Sc_(0.25)Nb_(0.25)Ti_(0.5))O_(3) alloys

摘要

A first-principles-derived approach is developed to study properties of two Pb(Sc_(0.25)Nb_(0.25)Ti_(0.5))O_(3) alloys that are both atomically ordered along the 001 direction. Unlike the first alloy, the second structure has differently-charged (001) B-planes. Both systems exhibit a global ferroelectric minimum of orthorhombic symmetry and a secondary ferroelectric minimum of tetragonal symmetry. Some electromechanical responses are enhanced in the secondary minimum, especially for the second structure. Mechanisms allowing a switch from the global to the secondary minimum are discussed.