Thermal expansion and phase transitions of Cd3As2 and Zn3As2

The lattice parameters of Cd3As2 and Zn3As2 at various temperatures between 23 and 700°C have been measured using a single crystal X-ray diffractometer. The phase transitions of both compounds have been investigated in detail. It is shown that the transition α → α′ goes on rather slowly and the existence of an intermediate phase is suspected. The transition α′ → α″ in Cd3As2 goes very quickly with a small thermal hysteresis. As a result of this transition the fourfould axis of the tetragonal cell changes its orientation, which occasionaly causes twinning. The crystal structure of the high temperature β-phase has been corroborated.