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

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 In-2(WO4)(3) were investigated. Results indicate that In2-xScx (WO4)(3) crystalizes in a monoclinic structure at 300 degrees 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 x 10(-6) degrees C-1. After sintering at 700 degrees 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 tempera- ture-induced phase transition temperature of In2-xScx (WO4)(3) ceramics from 250 degrees 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 x 10(-6) degrees C-1 and -4.43 x 10(-6) degrees C-1 in a wider temperature range of 25-700 degrees C, respectively.