Effect of Ba concentration on phase stability and mechanical and thermal properties of La2Mo2O9

Abstract

Ba-substituted La2Mo2O9 ((La1−xBax)2Mo2O9−δ, x=0–0.12) was prepared and the thermal and mechanical properties were evaluated. The thermal expansion coefficients (TECs) were determined from high-temperature X-ray diffraction (XRD) analysis. Phase transition in La2Mo2O9 was suppressed via substitution of Ba for La, as demonstrated by differential scanning calorimetry (DSC) analysis. The mechanical properties, such as the bulk modulus, shear modulus, Young’s modulus, compressibility, and Debye temperature were evaluated from the measured sound velocities. The thermal conductivity was evaluated from the thermal diffusivity, heat capacity, and density in the temperature range from room temperature to 1073K. The thermal conductivity decreased with increasing Ba content. Theoretical calculations based on the Klemens–Callaway model were performed to analyze the thermal conductivity, and the results suggest that the reduction of the thermal conductivity was mainly attributed to oxygen defects in the anion sublattice of La2Mo2O9.