Low thermal conductivity of Bi2Mo2O9 ceramics

Bismuth molybdate (Bi2Mo2O9, BMO) has drawn great attention as an excellent catalysis for partial oxidation of light olefins and microwave dielectric materials. Due to its complex crystal structure and intrinsically low thermal conductivity, BMO may be a possible candidate for thermal barrier coating and thermoelectric application. According to our knowledge, however, no related studies on this issue have been reported. In this work, polycrystalline BMO samples with high phase purity and density were synthesized by the solid state reaction method. Various thermophysical properties including thermal expansion coefficient, heat capacity and thermal conductivity were investigated for the first time as far as we know. BMO was found to exhibit a low thermal conductivity of 1 W/mK at room temperature. A close look was taken to the sound speed, Young's modulus and phonon mean free path, providing a detailed interpretation for the origin of this intrinsically low thermal conductivity.