Synthesis and negative thermal expansion properties of solid solutions Yb2−xLaxW3O12 (0 ≤ x ≤ 2)

A new series of rare earth solid solutions Yb2−xLaxW3O12 were successfully synthesized by the solid-state method. Effects of substituted ion lanthanum on the microstructures and thermal expansion properties in the resulting Yb2−xLaxW3O12 ceramics were investigated by X-ray diffraction (XRD), thermogravimetric analyzer (TGA), field emission scanning electron microscope (FESEM) and thermal mechanical analyzer (TMA). Results indicate that the structural phase transition of the Yb2−xLaxW3O12 changes from orthorhombic to monoclinic with increasing substituted content of lanthanum. The pure phases can form in the composition range of 0 ≤ x < 0.5 with orthorhombic structure and 1.5 < x ≤ 2 with monoclinic one. High lanthanum content leads to a low hygroscopicity of Yb2−xLaxW3O12. Negative thermal coefficients of the Yb2−xLaxW3O12 (0 ≤ x ≤ 2) also vary from −7.78 × 10−6 K−1 to 2.06 × 10−6 K−1 with increasing substituted content of lanthanum.