Theoretical prediction and experimental determination of the low lattice thermal conductivity of Lu2SiO5

In this paper, Lu2SiO5 is reported as a promising rare-earth silicate with very low thermal conductivity. First-principle method is used to calculate the crystal structure, second order elastic constants and anisotropic elastic stiffness. Using these parameters, the whole profile of temperature dependent lattice thermal conductivity of Lu2SiO5 is predicted based on well-established models. The low lattice thermal conductivity of Lu2SiO5 originates from its complex crystal structure, significant bonding heterogeneity, low Debye temperature, and low sound velocity. Experimental intrinsic lattice thermal conductivity is also determined by successfully eliminating the extrinsic mechanisms for phonon scattering by point defects and grain boundaries, as well as the contribution of thermal radiation at high temperatures, from the measured lattice thermal diffusivity. The experimental result agrees well with theoretical prediction. The present method can illustrate how specific material parameters govern lattice thermal conductivity and provide quantitative guideline in searching novel candidates with low thermal conductivity.