Edge-defined film-fed (EFG) growth of rare-earth orthovanadates REVO4 (RE = Y, Gd): Approaches to attain high-quality shaped growth

In spite of their superior laser and polarizer properties rare-earth orthov anadates (REVO4) single crystals have not been adopted yet into extensive i ndustrial applications because of crystal growth difficulties. The main pro blems of CZ technique are compositional change and diameter instability. Th is work presents the first attempt to apply the edge-defined film-fed growt h (EFG) technique by which well-shaped REVO4 crystals have been grown direc tly. The capillary properties of WO4 and GdVO4 melt have been measured. The appl icability of shaped growth for rare-earth orthovanadate family was approved by successful EFG growth of transparent rod-like macro-defect-free single crystals of YVO4 and GdVO4. We address two main approaches to enhance the q uality of EFG crystals: (i) meniscus and crystal shape stability dependence on die top shape and (ii) the strategy of effective operating control. Con cave die top was found to be the best choice for high-quality EFG growth of REVO4 along [001] direction. The spectral analysis of weight signal from g rowing crystal was shown to be a useful feedforward clue to prevent crystal linity degradation at a very early stage. A reasonable stability of the EFG process was achieved using [211], [101], [001] and [100] pulling direction s.