Defect-mediated multiple-enhancement of phonon scattering and decrement of thermal conductivity in (YxYb1-x)2SiO5 solid solution

Abstract

Rare earth (RE) silicates are promising candidates for environmental and thermal barrier coating (ETBC) materials. Low thermal conductivity is one of the main concerned thermal properties in ETBC design. We herein adopted multiple phonon scattering mechanisms to lower thermal conductivity of (YxYb1-x)2SiO5 solid solutions. Bulk samples were prepared by hot pressing method and RE atomic occupations, Raman spectra, thermal conductivities were measured as well as Debye temperature was obtained from temperature dependent Young's modulus. It is interesting to note that huge mass and size misfits between Yb and Y ions dominate the decrement of thermal conductivity. Furthermore, Yb2+ increases the concentration of oxygen vacancy, and it further decreases heat conduction. This work highlights the possible defect engineering in RE silicates for their advances in ETBC applications.