Ferroelastic phase transition compositional dependence for solid-solution [(Li_0.5Bi_0.5)_xBi_{1- x}][Mo_xV_1-x]O₄ scheelite-structured microwave dielectric ceramics

A compositional dependence on the ferroelastic phase transition in scheelite solid-solution [(Li_0.5Bi_0.5)_xBi _1-x][Mo_xV_1-x]O ₄ ceramics was characterized by the microwave dielectric data over the temperature range 10-420 K. As x values increased from 0.0 to 0.125, a dielectric temperature-dependent anomaly consistent with a phase transition decreased linearly from 528 K for the pure BiVO₄ end member to 264 K for the solid-solution composition at x = 0.125. With further increasing x, the transition temperature decreased sharply to approximately 45 K and became stable for x ≥ 0.52. The phase transition point for pure tetragonal (Li _0.5Bi_0.5)MoO₄ ceramics is approximately 43 K. As the x value increases, the Raman band of the [(Li_0.5Bi _0.5)_xBi_1-x][Mo_xV _1-x]O₄ ceramics at room temperature broadens and overlaps. Ferroelastic domain structures were observed as a function of composition with diffraction contrast imaging and high-resolution imaging with transmission electron microscopy. Structure-property relations are inferred from the microscopy observations and the Raman spectra.