Revealing the peculiar local behavior of manganese and cobalt in diffusion-doped calcium orthovanadate Ca(VO).

Laser Ca(VO) single crystals (СVO; space group 3, = 21) with crystallochemical formula Ca1Ca2Ca3Ca4(Ca5 + Са5А)(V1V2V3)O grown by the Czochralski method were doped with МnO (CVO:МnO) and СoO (CVO:CoO) by high-temperature diffusion annealing. Statistical and local structures were comprehensively studied by single-crystal and powder synchrotron X-ray diffraction and conventional single-crystal X-ray diffraction as well as by X-ray absorption spectroscopy for the first time. The presence of Mn ions with a mixed formal charge and Co ions in the Ca2 (monocapped trigonal prism), Ca3 (two-capped trigonal prism), and Ca4 (octahedron) sites was revealed by diffraction methods. The tetrahedral coordination and the coordination intermediate between tetrahedral and octahedral were established for Mn and Co ions, respectively. A fundamentally different structural behavior of dopant ions (concentration, formal charge, and coordination environment) in the CVO crystals doped with manganese in the form of MnO during the crystal growth or by high-temperature diffusion annealing was observed. The relationship between characteristic bands in the absorption, fluorescence, and excitation spectra of CVO:МnO and CVO:CoO samples and transition metals with specific formal charges is discussed.