Exploring low thermal conductivity Ba _1‐ <i> _x </i> Sr <i> _x </i> WO ₄ ceramics as novel thermal protection materials

Abstract Tungstate, with the molecular formula AWO 4 , has attracted widespread attention due to its outstanding applications in various fields. Ba 1‐ x Sr x WO 4 ( x = 0, 0.2, 0.4, 0.6, and 0.8) ceramics with a single‐phase scheelite structure are synthesized by the conventional solid phase reaction method. Their structural stability, micromorphology, and element distribution, thermal and mechanical properties are systematically investigated. The experimental thermal conductivity of all samples is 0.852–1.056 W·m −1 ·K −1 at 1173.15 K. An outstanding advantage of Ba 1‐ x Sr x WO 4 ceramics is that the coefficient of thermal expansion increases from 7.71 × 10 −6 K −1 ( x = 0) to 10.31 × 10 −6 K −1 ( x = 0.8) at 1173 K, indicating that the doping of Sr ion reduces the system energy during the lattice relaxation process and significantly improves the coefficient of thermal expansion. The thermal conductivity of Ba 1‐ x Sr x WO 4 ceramics is significantly lower than that of most low thermal conductivity candidate materials, such as Y 2 SiO 5 , SrZrO 3 , and La 2 Zr 2 O 7 . This study lays a foundation for the design of BaWO 4 scheelites with excellent thermal properties, which have high practical application value in the field of thermoelectric conversion and thermal protection.