GROWTH OF OXYGEN DEFICIENCY-FREE YVO(4) SINGLE-CRYSTAL BY TOP-SEEDED SOLUTION GROWTH TECHNIQUE

In spite of its excellent properties, yttrium orthovanadate (YVO4) laser host single crystal has not been successfully adopted into high-tech applications because of crystal growth difficulties in connection with oxygen loss. This work is the first to apply a top-seeded solution growth (TSSG) technique to YVO4, by which oxygen deficiency-free crystals can be directly grown. Since undesirable non-pentavalent vanadium oxides are continuously forming during the YVO4 growth process, the flux media, in addition to the conventional TSSG requirements, must prevent the formation of oxygen deficient yttrium vanadate crystals. From these multiple requirements, lithium metavanadate (LiVO3) was selected as the best solvent for YVO4 flux growth. LiVO3 has suitable solubility for YVO4, low ViScoSity, low vaporization without toxicity (in the 1200-1400-degrees-C working temperature range), and the oxygen deficient Li-V bronze (gamma-LiV2O5) can easily form in it, thus preventing oxygen defect formation in the yttrium vanadate crystals. Wanklyn's model and Viting and Timofeeva's calculation data were applied successfully for preliminary selection of the flux material. From the schematic V2O5-Li2O-V2O3 ternary and Y2O3-V2O5-Li2O-V2O3 quaternary systems, the phase relations of Li-V bronzes and YVO4 can be resolved much more easily than from the previous simple binary systems. The transparent, macro-defect-free single crystal sample grown by the TSSG technique illustrates the significance of these considerations and the promise of this growth technology for YVO4 crystals.