Growth and properties of manganese doped Ca3(VO4)2 single crystals

Abstract

Calcium orthovanadate Ca3(VO4)2 crystals with the whitlockite structure as nominally pure as doped with manganese ions have been grown by the Czochralski method from melt in air in the [100] direction. The single crystals of optical-quality were obtained for 0.05–2 wt% Mn2O3 doping level in the melt. X-ray diffraction analysis was carried out. Analyze of the parameters of diffraction peaks indicates the microstructure improving for manganese doped crystals. The absorption spectrum of doped Ca3(VO4)2:Mn is characterized by a combination of absorption bands specific for Mn2+, Mn3+ and Mn5+ ions, it was also proved by spectroscopic measurements. Two fluorescence spectra were observed under 670 nm excitation: narrow fluorescence line peaking at about 1180 nm, which quite well fits the position of Mn5+ ions and broad band peaking at 1250 nm, which quite well fits the position of Mn3+ ions. Fluorescence in the visible range was observed in Ca3(VO4)2:Mn crystal. The specific domain structure of ferroelectric Ca3(VO4)2 crystal was revealed by the method of selective chemical etching depending on crystal composition and thermal treatment. The anisotropic character of the optical properties of the material was estimated.