Links between non-180° domain and heterophase structures in ferroelectric solid solutions: from stress relief to phase contents

A model of a heterophase sample with interlayers is applied to describe some two-phase states in ferroelectric 0.69BiFe(1-) (x) Ga (x) O-3-0.31BaTiO(3) solid solutions with x = 0 - 0.06. Features of a coexistence of the rhombohedral and pseudocubic phases are first analysed at variations of a unit-cell parameter of the pseudocubic phase a(PC) in heterophases with x = const. Conditions for the complete stress relief at planar interfaces hold in the presence of non-180 & DEG; domains in the rhombohedral phase and at the aforementioned variations of a(PC) . Agreement between the calculated and experimental results on contents in 0.69BiFe(1-) (x) Ga (x) O-3-0.31BaTiO(3) at room temperature is achieved.