Trapping Mechanism Associated with Electron Delocalization and Tunneling of CaAl[sub 2]O[sub 4]:Ce[sup 3+], A Persistent Phosphor

A long afterglow phosphor, was prepared and studied. It exhibits a broad-band emission in the deep blue with a persistence time longer than 10 h. The ions occupy three distinct sites in this material, and the emission and excitation spectra from ions in these sites have been identified. The thermoluminescence spectra were obtained following irradiation at different wavelengths. Five traps were found: two of the traps, with depths of 0.67 and 0.82 eV, are filled by electron transport though the conduction band; the other three, with depths of 0.4, 0.46, and 0.6 eV, are filled by electrons tunneling from the 5d levels of adjacent ions. Photoconductivity measurements were also made which indicated that the lowest 5d levels of lie below the conduction band and that the ground state of is about 1.1-1.4 eV above the valence band of the host. © 2003 The Electrochemical Society. All rights reserved.