Growth of Ce3+-doped Li6Gd(BO3)3 Single Crystals under Ultralow Oxygen Partial Pressure

Ce3+-doped Li6(Gd0.99Ce0.01)(BO3)3 single crystals have been grown by the floating zone method in argon atmosphere with an ultralow oxygen partial pressure, pO2≈10-23 Pa (Condition A) or under a conventional reduction gas of diluted H2 (Condition B). The intensities of the excitation and emission spectra of such crystals in the UV–visible spectrum (VIS) region obtained by optical measurements under Condition A were 20% higher than those under Condition B. X-ray photoelectron spectroscopy (XPS) revealed that the ratio of Ce3+ to Ce4+ in crystals grown under Condition A was larger than that in crystals grown under Condition B.