Thermal conductivity/diffusivity of Nd3+ doped GdVO4, YVO4, LuVO4, and Y3Al5O12 by temperature wave analysis

Abstract

Thermal diffusivity and thermal conductivity of single crystals of Nd3+ doped GdVO4, YVO4, LuVO4, and Y3Al5O12 are precisely measured over a wide range of doping concentration from 0.5to15at.% by temperature wave analysis. Thermal diffusivity serves as the most sensitive parameter to detect the effect of doping on thermal properties, where Nd3+ doped GdVO4 exhibits a decrease in thermal diffusivity (it has changed about 20% in their values in the c axis) but an increase in heat capacity (only 1.7%). It has long been understood that the thermal conductivity of YVO4 is inferior to that of Y3Al5O12; however, the thermal conductivity of YVO4 in the c axis shows the highest value in all four crystals compared at 1at.% of Nd3+ doping concentration. Thermal conductivity exhibits a decrease (∝ε−1∕2, ε: mass variance) with an increase of doping concentration, that is characteristic of Klemens’ point defect model for the phonon scattering. In the numerical fitting, the anisotropic decrease of thermal conductivity in different crystal axes, [100], [001], and [110], is reflected as the different phonon velocities. The simulated and the experimental thermal conductivity show the various decreasing curvatures indicating that the effect of mass difference of the host and the doping cations serves as an important factor, as with the crystallographic anisotropy, on the thermal conductivity of the doped single crystals.