Zone refining technique of LiGd0.5Lu0.5F4 crystals

Abstract

Doped crystals with high neodymium concentrations present important optical properties for the attainment of ultrashort laser pulses. Thus, in this work it was studied the formation of LiGd0.5Lu0.5F4crystals by the zone refining technique. Since this material presents a melting behavior near the congruence and it is a promising host for Nd doping. The compound was synthesized from the respective fluorides and afterward it was submitted to one melting cycle with a translation rate of 2.5 mm/h, an hidrofluorinant atmosphere of HF was maintained during both processes. A characteristic three-zone bar was obtained, which is characterisitic of compounds with an incongruent melting behavior. The physical characterization of the ingot was carried out using differential thermal analysis, electronic scanning microscopy, energy dispersive spectrometry and by X-ray diffraction. A precipitation of the compound Gd0.75Lu0.25F3 was observed in the first part of the ingot. In the middle a stoichiometric compound has formed, and LiF was segregated toward the end of the ingot, resulting in a eutectic phase. Gd concentration data, as well as the calculated lattice parameters for samples extracted of the three regions of the ingot, showed that the Gd3+ ion was also segregated toward the end of the bar. It was concluded that due to the composition variation along the bar, this technique is not suitable for the purification of LiGd0.5Lu0.5F4.