Improvement of persistent phosphorescence of Ca0.9Sr0.1S: Bi3+ by codoping Tm3+

Persistent phosphors Ca0.9Sr0.1 S:0.01Bi(3+) and Ca0.9Sr0.1 S:0.01Bi(3+), 0.01Tm(3+) were prepared via solid chemical reactions at 1200 degrees C. Luminescence, excitation spectra, decays of afterglow and thermoluminescence were investigated. Blue persistent phosphorescent band of P-3(1)-S-1(0) transition of Bi3+ was observed at 453 nm with Stoke's shift of 45 nm. The influence of codoping of Tm3+ on phosphorescence was studied. It was found that adding Tm3+ to the mixed sulfide host created a new trapping center, and the brightness and the persistent time of the phosphor were improved by more than 35%. (C) 2000 Elsevier Science B.V. All rights reserved.