A thermodynamic potential for barium zirconate titanate solid solutions

Barium zirconate titanate[Ba(ZrxTi_(1−x))O_(3)]solid solutions are promising lead-free ferroelectric materials that have received substantial interest.Thermodynamic analysis based on phenomenological Landau–Devonshire theory is a powerful method for theoretical investigation of ferroelectric materials,but cannot be applied to Ba(ZrxTi1−x)O3 because there is no thermodynamic potential.In this paper,a thermodynamic potential for Ba(ZrxTi_(1−x))O_(3)(0≤x≤0.3)solid solutions is constructed,and then a thermodynamic analysis carried out.The results accurately reproduce known phase structures and their transition temperatures,with good agreement with experimentally measured polarization,dielectric,and piezoelectric constants.It is found that Ba(ZrxTi_(1−x))O_(3) solid solutions at room temperature have three phase boundaries,including a tetragonal–orthorhombic phase boundary at x=0.013,an orthorhombic–rhombohedral phase boundary at x=0.0798,and a rhombohedral–paraelectric phase boundary at x=0.2135.The results also indicate that the chemical composition-induced ferroelectric–paraelectric phase boundary has superior electromechanical properties,suggesting a new way to enhance electromechanical coupling in Ba(ZrxTi_(1−x))O_(3) solid solutions.