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

Abstract Solid solutions of In 2 −x Sc x W 3 O 12 (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 In 2 −x Sc x W 3 O 12 (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 In 2 W 3 O 12 ceramic undergoes a structure phase transition from monoclinic to orthorhombic at 248 °C. This phase transition temperature of In 2 W 3 O 12 can be easily shifted to a lower temperature by partly substituting the In 3+ with Sc 3+ . When the x value increased from 0 to 1, the phase transition temperatures of In 2− x Sc x W 3 O 12 (0≤ x ≤2) samples decreased from 248 to 47 °C. All the In 2 −x Sc x W 3 O 12 (0≤ x ≤2) ceramics show fine negative thermal expansion below their corresponding phase transition temperatures. The negative thermal expansion coefficients of the In 2 −x Sc x W 3 O 12 (0≤ x ≤2) ceramics change in the range from −1.08×10 −6 °C −1 to −7.13×10 −6 °C −1 .