The cationic clathrate Si46−2xP2xTex crystal growth by chemical vapour transport

Crystals of the cationic clathrate Si46−2xP2xTex can be grown via chemical vapour transport by adding tellurium tetrachloride. The transport proceeds in the temperature gradient T1=923 K→T2=1003 K and with increasing temperature under reversion of the transport direction T2=1173 K→T1=1073 K. By means of the thermodynamic modelling of solid state-gas phase equilibria, the transport mechanism for both directions was clarified; in the direction T1→T2 (T1T1) SiCl4(g) becomes active. Using the modelling the composition of the crystals Si46−2xP2xTex can be predicted depending on the experimental conditions, i.e. the temperature range, the direction of temperature gradient and the composition of the starting material.