Phase transition and negative thermal expansion properties in isovalently substituted In2−xScx(MoO4)3 ceramics

Sc-substituted In2−xScx(MoO4)3 (0 ≤ x ≤ 2) ceramics were successfully synthesized by the solid state reaction method with the goal of tuning the phase transition temperature. Effects of Sc3+ substitution on the phase composition, microstructure, phase transition temperature and thermal expansion behavior of the In2−xScx(MoO4)3 (0 ≤ x ≤ 2) ceramics were investigated using XRD, FESEM, EDX, XPS and TMA, respectively. The results indicate that all samples are single phase. The relative densities of the In2−xScx(MoO4)3 ceramics increased gradually with increasing Sc3+ content. Investigations on thermal expansion properties of the In2−xScx(MoO4)3 ceramics reveal that the temperature-induced phase transition from monoclinic to orthorhombic symmetry is strongly correlated to the Sc3+ content. The obtained In2(MoO4)3 ceramics undergoes a structural phase transition from monoclinic to orthorhombic around 355.3 °C. The phase transition temperature can be significantly shifted from 355.3 °C (x = 0) to 31.9 °C (x = 1.5) by partially replacing In3+ cations with less electronegative Sc3+ cations. All In2−xScx(MoO4)3 (0 ≤ x ≤ 2) ceramics exhibit strong negative thermal expansion above the phase transition temperature. In0.5Sc1.5(MoO4)3 exhibits linear NTE over the 100-700 °C temperature range with a linear coefficient of thermal expansion of −3.99 × 10−6 °C −1.