Domain structure in the ferroelastic langbeinite K2Cd1.6Mn0.4(SO4)(3)

The ferroelastic phase transition in K2Cd1.6Mn0.4(SO4)(3) Solid solution wa s investigated by optical microscopy method. The existence of the permissib le domain structure in those compounds in whole temperature region below 23 F222 second order phase transition was found. it was shown that in the crys tals which belong to the isolated point, the domain walls are permissible d ue to enantiomorphic twinning. The determined orientation of domain walls i s {110}. The investigation of the topography of the optical activity shows the change of optical rotary power in some regions in 23 phase of K2Cd0.4Mn 1.6(SO4)(3) crystals. Obtained results are discussed on the base of thermod ynamic potential and prototype phase with point group symmetry (4) over bar 3m.