Synthesis and negative thermal expansion property of Y2−xLaxW3O12 (0≤x≤2)

Y2−xLaxW3O12 solid solutions were successfully synthesized by the solid state reaction method. The microstructure, hygroscopicity and thermal expansion property of the resulting samples were investigated by X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM) and thermal mechanical analysis (TMA). Results indicate that the structural phase transition of the Y2−xLaxW3O12 changes from orthorhombic to monoclinic with increasing substituted content of lanthanum. The pure phase can form for 0≤x≤0.4 with orthorhombic structure and for 1.5≤x≤2 with monoclinic one. High lanthanum content leads to a low relative density of Y2−xLaxW3O12 ceramic. Thermal expansion coefficients of the Y2−xLaxW3O12 (0≤x≤2) ceramics also vary from −9.59×10−6 K−1 to 2.06×10−6 K−1 with increasing substituted content of lanthanum. The obtained Y0.25La1.75W3O12 ceramic shows almost zero thermal expansion and its average linear thermal expansion coefficient is −0.66×10−6 K−1 from 103 °C to 700 °C.