Preparation of Cd3As2 and CdAs2 crystals by transport reaction in vapour phase

A method of preparation of Cd₃As₂ and CdAs₂ single crystals employing transport reaction in vapour phase without transport gas is described. Optimum conditions for growth of the crystals are determined. In the case of Cd₃As₂ the average temperature and the temperature gradient are 535 °C and 3·3 °C/cm respectively, in the case of CdAs₂ the corresponding values are 550 °C and 4 °C/cm. Bulk crystals as large as a few cm³ can be obtained within several days using evacuated quartz tubes 150 mm in length and 20 mm in diameter. Furthermore, thermodynamical arguments indicating possible reaction mechanisms are presented. Sublimation appears to be the most probable mechanism of transport in the case of Cd₃As₂, whereas the process is more complicated in the case of involving the decay of CdAs₂ molecules.