Phase transition and negative thermal expansion in orthorhombic Dy2W3O12

Abstract

New materials with suitable negative thermal expansion (NTE) are much desired to control thermal expansion in solids. In the present study, we determined the phase transition temperature of Dy₂W₃O₁₂ from the monoclinic phase to the orthorhombic phase at 996 °C. The orthorhombic phase could be retained by quenching, and further high temperature XRD and synchrotron radiation X-ray powder diffraction (SXRD) experiments revealed that Dy₂W₃O₁₂ shows NTE (−2.6 × 10⁻⁵ °C⁻¹) in the temperature range of 150–500 °C, which is the largest negative thermal expansion in the A₂W₃O₁₂ family (A = rare earth element). A possible NTE mechanism and enhanced NTE were elucidated by the transverse thermal motion of the bridge oxygen in A–O–W linkages accompanied by distortion of the polyhedra with large Dy³⁺ on the A site.