Finite-temperature properties of (BiFeO3)x(BaTiO3)1-x solid solutions

We use a first-principles based approach to theoretically investigate the room-temperature phase diagram of (BiFeO3)(x)(BaTiO3)(1-x) solid solutions. Using a modified effective Hamiltonian scheme, we show that random fields originating from off-valent substitutions decrease the ferroelectric transition temperature leading to a paraelectric ground state in the intermediate range of concentrations x. The predicted critical concentrations at which lattice distortions inherited from the ferroelectric phases of parent compounds vanish fall within the range of the experimental values. Furthermore, the obtained results give the necessary microscopical insight into the mechanism driving the pseudocubic phase formation.