Systematics of phase transitions induced by hydrostatic pressure in AIIBIII2 CVI4 ordered-vacancy compounds

Investigation of phase transitions related to changes in the crystalline structure of solid state materials represents an extremely important area of condensed mater physics, since they lead to reconfiguration of all the solid state physical properties, including electrical, optical, vibrational, elastic and mechanical properties. Hydrostatic pressure is one of the basic factors leading to the realization of phase transitions. Gaining knowledge of regularities and peculiarities of pressure induced phase transitions is important both from the fundamental and applicative point of view. In spite of multilateral investigation of this subject in elemental, binary and some ternary compounds, less attention has been paid to ordered-vacancy compounds. At the same time, possibilities to control the stoichiometric defects by applying hydrostatic pressure open new opportunities for defect engineering in such compounds. This review paper summarizes the results of investigations of phase transitions in ternary AIIBIII 2CVI 4 compounds, which represent a subclass of ordered-vacancy compounds. Investigations were performed by Raman spectroscopy, X-ray diffraction, and optical absorption spectroscopy in crystals with initial crystallographic structure from three categories, including tetragonal, spinel, and rhombohedral layered structures. The dynamics of pressure induced changes is described. The regularities and the systematics of phase transitions in this class of semiconductor materials are revealed.