Pressure behaviour of birefringence in [(CH3)2CHNH3)]4Cd3Cl10 crystal

The studies of birefringence of [(CH3)2CHNH3)]4Cd3Cl10 single crystal were carried out in the temperature interval 240–420 K and in the hydrostatic pressure range up to 570 MPa. The shift of temperature of phase transition at T1 to higher temperature is observed with increase of pressure with the pressure coefficient dT 1 / dp = 0.233 K / MPa . The shift of phase transition at T2 to higher temperatures with the pressure coefficient dT 2 / dp = 0.063 K / MPa is observed up to about 250 MPa. At temperature TPCP=310 K and pressure pPCP=310 MPa the character of continuous phase transition changes to there first order and it corresponds to the tricritical point existence. Based on the studies of the temperature and pressure dependences of birefringence of [(CH3)2CHNH3)]4Cd3Cl10 crystal, its (p,T) phase diagram was constructed and its main features were discussed.