Trap levels in CaGa2S4 co-doped with Eu and rare earth elements

Long afterglows are observed in the case of co-doping CaGa2S4 with Eu and one of the other rare earth elements (REEs). Thermoluminescence spectra of these compounds have been measured in order to determine their trap depths. Photoluminescence spectra and decay curves have been also observed. The emission intensities, decay times and trap depths are shown as a function of the f-electron number of REEs, and the correlation between these properties and the 4f and 5d levels of divalent and trivalent REEs in the band structure of CaGa2S4 is discussed. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)