Spectroscopy and X-ray diffraction analysis of europium molybdate single crystals subjected to different thermobaric treatments

Europium molybdate (EMO) single crystals subjected to high uniform pressures (Pβ’-EMO) (exposure under 9 GPa at 300 K for 7 days) have been investigated by optical spectroscopy and X-ray diffraction. It is shown that Pβ’-EMO and amorphous europium molybdate have similar luminescence and transmission spectra. Annealing of EMO single crystals subjected to thermobaric treatments exhibits the same sequence of phase transitions as in the case of annealing of amorphous europium molybdate. It is shown that an EMO single crystal in the high-pressure state is a structurally inhomogeneous material consisting of two domains: a dominant amorphous-like part, in which the long-range order is completely absent, and a minor crystalline part.