Unusual luminescence behaviour of terbium phosphate glasses

While preparing a terbium-containing phosphate glass, an intense emission of green light was observed when the melt was poured into a metal mould. This emission was easily visible to the naked eye and was only observed on quenching of the melts. To our knowledge this phenomenon, termed ‘cooling-induced luminescence (CIL)’, has not previously been reported. Experimental evidence suggests that the CIL may be related to a thermally induced shift in the oxidation-reduction balance in the melt. A similar phenomenon was also observed with europium phosphate melts.