The effect of hydrostatic pressure up to 120 MPa on the stability boundaries of crystalline phases and phase transition behaviour observed in MSiF6 . 6H2O (M = Fe, Co, Ni) in the temperature range 20-300 K, is studied by X-ray diffractometry and the differential thermal analysis technique. Existence of critical pressures and the destabilization of the low-temperature monoclinic phase in FeSiF6 . 6H2O and CoSiF6 . 6H2O are established. P-T diagrams of the investigated fluosilicate hexahydrates showing the unique variety of phases and phase transitions are plotted. It is shown that the P-T phase diagram of crystalline states NiSiF6 . 6H2O has the same form as the diagram region CoSiF6 . 6H2O corresponding to pressures which exceed the critical pressure for the stability of the monoclinic phase.
|Number of pages||6|
|Journal||Physical review B|
|Publication status||Published - Oct 1992|
- ORIENTATIONAL PERIODIC ANTIPHASE