Crystal growth of pure and doped-KGd(WO 4) 2 and their characterization for laser applications

Abstract

Potassium gadolinium tungstate [KGd(WO 4) 2] single crystals have been grown by the top-seeded solution growth method (TSSG) and modified Czochralski techniques. Several flux systems, e.g. K 2WO 4, K 2W 2O 7, K 2W 3O 10, etc. have been used for the growth from solution. With different flux systems, the saturation and seeding temperatures vary considerably. The cooling rate of 0.1° h −1 and seed rotation rate of 20 rpm, after seeding, yields good-quality crystals. The grown crystals were cut and polished and the undoped KGW was transparent. The color of the doped crystals varies from deep violet to transparent violet depending on the concentration of Nd dopants. Co-doping Yb with Nd: KGW slightly improves the transparency of the crystals. X-ray powder diffraction results confirm the α-phase of the grown crystals and the peaks corresponding to different phases were indexed. No impurity peaks were present in the X-ray diffractogram. The presence of dopants Nd, Yb, Nd+Yb and their concentration in the doped crystals were confirmed with EDAX analysis. Raman spectra confirm the composition and structural stability of the grown crystals. The peaks corresponding to impurities like CO 2 and H 2O stretching are completely absent. The prominent Raman line for these crystals was identified at 904 cm −1 from the Raman spectra of the as grown crystals.