In 2Mo 3O 12: A low negative thermal expansion compound

Orthorhombic In ₂Mo ₃O ₁₂ has low negative linear coefficient of thermal expansion ( α _l = ‑1.85 × 10 ^‑6 °C ^‑1) as evaluated by X-ray powder diffraction using a synchrotron facility. The linear coefficient of thermal expansion for orthorhombic In ₂Mo ₃O ₁₂ is directly dependent on the inherent volume distortion parameter ( υ) of InO ₆. This finding strongly corroborates the recently proposed relationship between the linear coefficient of thermal expansion in A ₂ M ₃O ₁₂ compounds ( α _l) and the distortion level of AO ₆ polyhedra. With the increase of inherent distortion parameter ( υ) of AO ₆ polyhedra, the linear coefficient of thermal expansion becomes more negative. Another important feature of AO ₆ polyhedra, including InO ₆, is that their distortion increases as a function of temperature. Orthorhombic In ₂Mo ₃O ₁₂ is stable in the studied temperature range, 370–760 °C.