Studies on the decay characteristics of strontium aluminate phosphor on thermal treatment

Strontium aluminate (SRA) based long decay phosphor has been prepared by solid-state reaction technique. The dependence of initial brightness and observed afterglow characteristics on various thermal processing parameters such as heating rates, time of constant heating and cooling rates have been investigated. It has been found that heating rates (>625degreesC h(-1)), time of constant heating (<2h at around 1200degreesC) and cooling rates (>250degreesC h(-1)) resulted in non-uniform luminescent samples which are not excited under roomlight but under UV (365 nm). Whereas heating rates (<300 degreesC h(-1)), time of constant heating (>4 h at 1200degreesC) and cooling rates (<100degreesC h(-1)) resulted in high-density ceramic compact (similar to3100 kg m(-3)) samples with very low initial brightness but quite long afterglow under roomlight and UV excitation. An optimum of both fast rise and long afterglow under roomlight excitation has been achieved for the SRA samples fired with the heating rates of 300-625degreesC h(-1), time of constant heating 2-4 hat around 1200degreesC and cooling rates of 100-250degreesC h(-1). The decay characteristics of SRA have been compared with established ZnS:Cu long decay phosphor. (C) 2002 Elsevier Science B.V. All rights reserved.