Structural phase transitions in Cu2–xFeyS crystals

Crystals with Cu_2−xFe_yS compositions (x = 0.30, 0.25, 0.20, 0.15; y = 0.05) have been synthetized and obtained by the method of slow cooling. X-ray diffractometric studies have shown that at room temperature the above crystals consist of an orthorhombic phase (anilite), a monoclinic phase (djurlite), and their metastable high-temperature facecentered cubic phases (FCC)₁ and (FCC)₂, respectively. A crystallographic relation has been found between the lattices of the orthorhombic, monoclinic and (FCC)₁ phase. It is shown that all these phases transform in the final analysis to a single high-temperature fcc phase. All the transitions are reversible, i.e. in the course of inverse cooling to room temperature, the diffraction patterns are restored completely in reverse order.