Densification and negative thermal expansion property of In0.5Sc1.5(MoO4)3 ceramics

Orthorhombic In0.5Sc1.5(MoO4)3 ceramics with 3 wt% MgO as sintering aid were synthesized via solid state method at various temperatures. The effects of sintering temperature and 3 wt% MgO additive on the microstructure, density and negative thermal expansion property of the In0.5Sc1.5(MoO4)3 ceramics were examined using XRD, SEM and TMA. The results indicate that the increase of twice-sintering temperature promotes densification, and the grain size grows from 1 μm to 7 μm. When the twice-sintering temperature is further raised to 1200 °C, impurity Sc2O3 is detected due to the decomposition of In0.5Sc1.5(MoO4)3. The introduction of MgO as a sintering aid strongly affects the densification and negative thermal expansion stability of the In0.5Sc1.5(MoO4)3 ceramics owing to the formation of the liquid phase MgMoO4. The In0.5Sc1.5(MoO4)3 ceramics with 3 wt% MgO show more stable negative thermal expansion, and their average linear coefficients of thermal expansion (CTEs) are all tested to be between 4 × 10 −6 °C−1 and 5 × 10 −6 °C−1 at 30–700 °C. The variable temperature XRD results reveal In0.5Sc1.5(MoO4)3 shows anisotropic negative thermal expansion. The average CTEs of In0.5Sc1.5(MoO4)3 along a, b and c-axis are calculated to be −4.86 × 10 −6 °C−1, 4.25 × 10 −6 °C−1 and -3.25 × 10 −6 °C−1, respectively, and the volumetric CTE is calculated to be −3.83 × 10 −6 °C−1 at 25–700 °C. •Orthorhombic In0.5Sc1.5(MoO4)3 ceramics were synthesized via solid state method.•Increasing sintering temperatures promote density of In0.5Sc1.5(MoO4)3 ceramics.•MgO additive affects densification and stability of In0.5Sc1.5(MoO4)3 ceramics.•In0.5Sc1.5(MoO4)3 shows anisotropic negative thermal expansion.•CTEs of samples with MgO are all tested to be 4–5 × 10 −6 °C−1 at 30–700 °C.