Preparation of Al_2 (WO_4)_3 Powders with Negative Thermal Expansion Performance by Solid Phase Reaction

Negative thermal expansion material Al_2 (WO_4)_3 powders were prepared by solid state reaction using aluminum oxide and tungsten trioxide as raw materials.The phase,crystal structure and morphology of the powders were characterized by powder X-ray diffraction(XRD)and scanning electron microscopy(SEM)respectively. The thermodynamic property of the powders was characterized by thermo gravimetric and differential thermal analysis(TG-DTA).The thermal expansion coefficients of Al_2 (WO_4)_3 powders were measured by thermal dilatometer.The results show that the sample is Al_2(WO_4)_3 with high purity and orthorhombic structure.The particles have regular morphology and the size distribution is homogeneous,which is 0.6μm×0.4μm averagely. The powders have no phase transition and decomposition in the temperature range from room-temperature to the melting point.The average thermal expansion coefficient of the powders is—1.56×10~(-6) K~(-1) in the temperature range of 30—900℃.