Revealing the peculiar local behavior of manganese and cobalt in diffusion-doped calcium orthovanadate Ca 3 (VO 4 ) 2 .

Laser Ca 3 (VO 4 ) 2 single crystals (СVO; space group R 3 c , Z = 21) with crystallochemical formula Ca1 18 Ca2 18 Ca3 18 Ca4 6 (Ca5 + Са5А) 3 (V1 18 V2 18 V3 6 )O 168 grown by the Czochralski method were doped with Мn 2 O 3 (CVO:Мn 2 O 3 ) and Сo 3 O 4 (CVO:Co 3 O 4 ) 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 (2+ δ )+ ions with a mixed formal charge and Co 2+ 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 (2+ δ )+ and Co 2+ 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 Mn 2 O 3 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:Мn 2 O 3 and CVO:Co 3 O 4 samples and transition metals with specific formal charges is discussed.