Revealing the peculiar local behavior of manganese and cobalt in diffusion-doped calcium orthovanadate Ca₃(VO₄)₂

Abstract

Laser Ca3(VO4)2 single crystals (СVO; space group R3c, Z = 21) with crystallochemical formula Ca118Ca218Ca318Ca46(Ca5 + Са5А)3(V118V218V36)O168 grown by the Czochralski method were doped with Мn2O3 (CVO:Мn2O3) and Сo3O4 (CVO:Co3O4)...

Annealing-Induced Structural Behavior of Mn Dopant Ions in Calcium Orthovanadate Ca3(VO4)2 Single Crystals

“…In the latter case, manganese ions first occupy the general position Ca5A with an octahedral environment, and with an increase in the content of manganese ions, they begin to enter the defect position Ca5. • in the CVO:Mn 2 O 3 structure, 11 manganese occupies the Ca2 (according to S), Ca3, Ca4 (according to D and S), and Ca5 (according to D data) sites. Manganese ions are not detected in the Ca1 site.…”

“…Due to the fact that tetrahedral and octahedral coordinations are typical for transition-metal ions in the structures of oxide systems, and manganese ions, according to structural analysis, occupy the Ca3 crystallographic site with a distorted two-capped trigonal prismatic coordination, the actual coordination of manganese ions is either tetrahedral or octahedral, which was confirmed by Kuz'micheva et al 10,11 Comparing the compositions of CVO:0.05Mn (D) and CVO:0.05Mn (S) with different FC Mn and a unit cell parameter, an interesting picture is observed: the parameter correlates with the numerical value of the formal charge of the manganese ion rather than its content in the sample.…”

“…(5) According to diffraction data, manganese ions with FC = 5+ are absent in all crystallographic sites of the studied structures CVO:Mn 10 and CVO:Mn 2 O 3 , 11 which is confirmed by XAS. The refinement of the structure of CVO:0.05Mn microcrystals was performed based on single-crystal conventional (D) and synchrotron (S) X-ray diffraction data (see Supporting Tables S1−S3).…”

“…7−11 The introduction of manganese ions into the CVO crystal matrix can be carried out by two methods: either during the crystal growth process by the Czochralski method, where the doping impurity is introduced into the melt in the form of Mn 2 O 3 oxide (CVO:Mn), 7,8,10 or by high-temperature diffusion doping of the as-grown single crystal from the solid-state impurity source (diffusant), namely, Mn 2 O 3 powder (CVO:Mn 2 O 3 ). 9,11 In this case, the doping method affects the structural position, local environment, and formal charge of Mn ions in the CVO structure, as well as the color of the samples. 10,11 A concentration series of CVO crystals doped with manganese was grown by the Czochralski method.…”

“…9,11 In this case, the doping method affects the structural position, local environment, and formal charge of Mn ions in the CVO structure, as well as the color of the samples. 10,11 A concentration series of CVO crystals doped with manganese was grown by the Czochralski method. 8 Mn 2 O 3 was added into the melt with a concentration exceeding the stoichiometric composition by 0.05−1.0 wt %.…”