Synthesis, phase transition and negative thermal expansion of cubic Zr(W1−yMoy)2−xVxO8−x/2 (y = 0.10, 0.20, 0.30, 0.40; 0 ⩽ x ⩽ 0.40) solid solutions

Abstract

We first prepared tetragonal Zr(W1−yMoy)2−xVxO7−x/2(OH)2⋅2H2O (y=0.10, 0.20, 0.30, 0.40; 0⩽x⩽0.40) hydrate precursors through acidic steam hydrothermal (ASH) treatment. Dehydration of these precursors produces the corresponding low temperature orthorhombic polymorph Zr(W1−yMoy)2−xVxO8−x/2. Upon annealing at 813–873K for 2h this intermediate further transforms to the end product of kinetically favored cubic Zr(W1−yMoy)2−xVxO8−x/2 solid solutions. The dehydration and orthorhombic to cubic phase transition temperatures decrease linearly with increasing Mo and constant V content; the orthorhombic to cubic phase transition temperature also decreases linearly with increasing V content at constant W/Mo ratio. Measurements of thermal stability and expansion indicate that cubic Zr(W1−yMoy)2−xVxO8−x/2 solid solutions have strong negative thermal expansion property. We characterized the average structure of c-Zr(W0.90Mo0.10)1.76V0.24O7.88 using Rietveld refinement method, calculated lattice parameters of solid solutions and solid solubility at different y value, and discuss structural factors that affect cell parameter values.