Abstract
Calcium orthovanadate Ca3(VO4)2 (CVO) is an efficient media for laser applications. Czochralski-grown green CVO single crystals doped with over-stoichiometric 0.1 (CVO:0.1Mn) and 1.0 wt.%Mn (CVO:1.0Mn) were studied by X-ray diffraction and X-ray absorption spectroscopy for the first time. In the CVO:1.0Mn, an occurrence of Mn3+ in Ca3 (two-capped trigonal prism), Ca4 (distorted octahedron), and defective Ca5 and Ca5A (highly-distorted octahedron) sites and vacancies in V2 and V3 sites (distorted tetrahedra) were revealed. In the CVO:0.1Mn, a presence of Mn3+ in Ca3 and Ca5A sites and vacancies in V2 site were found. In the CVO, the Mn3+ form elongated octahedra (tetragonal bipyramid; coordination number, 4 + 2) typical for the Jahn-Teller ions. Models for the rearrangement of Ca3 and Ca4 polyhedra into a tetragonal bipyramid are proposed. Along with the Mn3+, the Mn2+ and Mn5+ ions were observed by optical spectroscopy in CVO:0.1Mn (predominantly Mn2+ ions) and CVO:1.0Mn (only Mn5+ ions).
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