Thermal properties of the nonlinear optical crystal zinc tris (thiourea) sulphate

Abstract

The heat capacity of crystalline zinc tris (thiourea) sulphate, has been measured in the range from 220 to 500 K by differential scanning calorimetry, and was found to obey the relationship Cp(T)=2.76×10−3 T+0.366 J g−1 K−1. Thermal expansion data have been measured in the range from 150 to 473 K. From these data, the principal thermal expansion coefficients were found to be α1=6.41×10−5 K−1, α2=4.52×10−5 K−1, and α3=−4.32×10−6 K−1. The thermal conductivity tensor of this orthorhombic crystal was calculated from values of the thermal diffusivity in the directions normal to the (100), (010), and (001) crystal planes by the laser flash method. The thermal conductivity coefficients at 295 K are k1=0.27 W m−1 K−1, k2=0.34 W m−1 K−1, and k3=0.54 W m−1 K−1.