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

Calcium orthovanadate Ca-3(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 Ca-3(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 Ca-3(VO4)(2):Mn crystal. The specific domain structure of ferroelectric Ca-3(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.