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

Abstract Orthorhombic In 0.5 Sc 1.5 (MoO 4 ) 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 In 0.5 Sc 1.5 (MoO 4 ) 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 Sc 2 O 3 is detected due to the decomposition of In 0.5 Sc 1.5 (MoO 4 ) 3 . The introduction of MgO as a sintering aid strongly affects the densification and negative thermal expansion stability of the In 0.5 Sc 1.5 (MoO 4 ) 3 ceramics owing to the formation of the liquid phase MgMoO 4 . The In 0.5 Sc 1.5 (MoO 4 ) 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 In 0.5 Sc 1.5 (MoO 4 ) 3 shows anisotropic negative thermal expansion. The average CTEs of In 0.5 Sc 1.5 (MoO 4 ) 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.