Effect of isovalent substitution on phase transition and negative thermal expansion of In2−xScxW3O12 ceramics

Solid solutions of In2−xScxW3O12 (0≤x≤2) were successfully synthesized using the solid state reaction method. Effects of substituted scandium content on the phase composition, microstructure, phase transition temperatures and thermal expansion behaviors of the resulting In2−xScxW3O12 (0≤x≤2) samples were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and thermal mechanical analyzer (TMA). Results indicate that the obtained In2W3O12 ceramic undergoes a structure phase transition from monoclinic to orthorhombic at 248 °C. This phase transition temperature of In2W3O12 can be easily shifted to a lower temperature by partly substituting the In3+ with Sc3+. When the x value increased from 0 to 1, the phase transition temperatures of In2−xScxW3O12 (0≤x≤2) samples decreased from 248 to 47 °C. All the In2−xScxW3O12 (0≤x≤2) ceramics show fine negative thermal expansion below their corresponding phase transition temperatures. The negative thermal expansion coefficients of the In2−xScxW3O12 (0≤x≤2) ceramics change in the range from −1.08×10−6 °C−1 to −7.13×10−6 °C−1.