Thermal expansion properties of Ln2−xCrxMo3O12 (Ln = Er and Y)

Structures and thermal expansion properties of Ln2−xCrxMo3O12 (Ln = Er and Y) have been investigated by X-ray powder diffraction. Rietveld analysis results of Ln2−xCrxMo3O12 indicate that compounds Er2−xCrxMo3O12 (0 ≤ x ≤ 0.3) and Y2−xCrxMo3O12 (0 ≤ x ≤ 0.2) crystallize in orthorhombic structure and exhibit negative thermal expansion, while both monoclinic and orthorhombic compounds Er2−xCrxMo3O12 (1.7 ≤ x ≤ 2.0) and Y2−xCrxMo3O12 (1.8 ≤ x ≤ 2.0) possess positive coefficient of thermal expansion. The coefficients of linear thermal expansion of orthorhombic Ln2−xCrxMo3O12 change from negative to positive with increasing chromium content. Thermogravimetric and differential scanning calorimetry have been used to study the hygroscopicity and the phase transition temperature.