Thermal expansion studies of Gd2Mo3O12 and Gd2W3O12

Simultaneous thermogravimetric/differential thermal analysis of Gd₂Mo₃O₁₂ showed an irreversible phase transition at 1178 K where as Gd₂W₃O₁₂ showed reversible phase transition at 1433 K, which were confirmed by powder X-ray diffraction. The thermal expansion behavior of α-Gd₂Mo₃O₁₂ (room temperature phase), β-Gd₂Mo₃O₁₂ (phase obtained by heating Gd₂Mo₃O₁₂ at 1223 K) and Gd₂W₃O₁₂ have been investigated using high temperature X-ray diffractometer. The cell volume of α-Gd₂Mo₃O₁₂, β-Gd₂Mo₃O₁₂ and Gd₂W₃O₁₂, fit into polynomial expression with respect to temperature, showed positive thermal expansion up to 1073, 1173 and 1173 K, respectively. The average volume expansion coefficients for α-Gd₂Mo₃O₁₂, β-Gd₂Mo₃O₁₂ and Gd₂W₃O₁₂ are 39.52 × 10⁻⁶, 21.23 × 10⁻⁶ and 37.96 × 10⁻⁶ K⁻¹, respectively.