Understanding energy transfer in Ce doped Li6Gd(BO3)3: A study of millisecond decay kinetics in 77–300 K range

Large size, transparent and crack-free single crystals of pure and 0.1 mol% Ce doped Li6Gd(BO3)3 have been grown using the Czochralski technique. The photoluminescence and decay kinetics in millisecond range were investigated in the 77–300 K temperature range. In the case of Ce doped single crystals a broad emission band at 400 nm corresponding to 5d→4f transitions of Ce3+ centers has been observed near room temperature. This emission band splits into two peaks at 386 nm and 414 nm below 200 K. The temperature dependence of Ce3+ emission corresponding to excitation bands at 312 and 345 nm were studied. It was observed that for an excitation at 345 nm (corresponding to the Ce3+ ions alone) the emission intensity decreases with increasing temperatures while it remains constant for the excitation of Ce3+ at 312 nm that coincides with the Gd3+ energy level at the same wavelength. This suggests the participation of a temperature dependent energy transfer mechanism between Gd3+ and Ce3+ ions in the Li6Gd(BO3)3 matrix. The mechanism has been explained by studying the temperature dependence of Gd3+ emission at 312 nm in the doped and undoped crystals.