Negative Thermal Expansion in (HfMg)(WO ₄ ) ₃

Abstract

A single‐phase material (HfMg)(WO 4 ) 3 with an orthorhombic structure, A 2 (WO 4 ) 3 ‐type tungstate, has been successfully prepared for the first time by the calcination of HfO 2 , MgO, and WO 3 , substituting Hf 4+ and Mg 2+ for A 3+ cations in A 2 (WO 4 ) 3 . The new material shows a negative thermal expansion coefficient of approximately −2 ppm/°C from room temperature to 800°C. The mechanism of negative thermal expansion is assumed to be the same as that of Sc 2 (WO 4 ) 3 .