Negative thermal expansion coefficient of Sc-doped indium tungstate ceramics synthesized by co-precipitation

Abstract

Co-precipitation was successfully applied to synthesize the Sc3+ doped In2-xScx (WO4)3 (x = 0, 0.3, 0.6, 0.9 and 1.2) compounds. The composition- and temperature-induced structural phase transition and thermal expansion behaviors of Sc3+ doped In2(WO4)3 were investigated. Results indicate that In2-xScx (WO4)3 crystalizes in a monoclinic structure at 300 °C for x ≤ 0.3 and changes into hexagonal structure for x ≥ 0.6. Hexagonal In1.1Sc0.9(WO4)3 displays negative thermal expansion (NTE) with an average linear coefficient of thermal expansion (CTE) of −1.85 × 10−6 °C −1. After sintering at 700 °C and above, a phase transition from hexagonal to orthorhombic phase was observed in In2-xScx (WO4)3 (x ≥ 0.6). Sc3+ doping successfully reduce the temperature-induced phase transition temperature of In2-xScx (WO4)3 ceramics from 250 °C (x = 0) to room temperature (x = 0.9). When x = 0.9 and 1.2, the average linear CTEs of In2-xScx (WO4)3 ceramics are −5.45 × 10−6 °C−1 and -4.43 × 10−6 °C−1 in a wider temperature range of 25–700 °C, respectively.