Analysis of electron and hole trap states in novel storage phosphors: Undoped, Eu-doped, and Ce-doped CsCaCl3 ceramics

Abstract

The electron and hole trap states of undoped, Eu-doped, and Ce-doped CsCaCl3 were analyzed using the absorption spectra and the TSL glow curves after the optical bleaching. The trap depths were estimated using the initial rise method. In CsCaCl3, F centers were the electron trap centers, and Vk centers stabilized by defects or impurities (referred to as Vk′ centers) were one type of the hole trap centers. The recombination of F–Vk′ centers occurred around 400–420 K. In addition to Vk′ centers, V2 centers, V3 centers, and V3 centers perturbed by dopant ions were also the hole trap centers. In Eu-doped CsCaCl3 ceramics, Eu-related hole centers were found, and their trap depths were estimated to be 1.55 and 1.63 eV. For the Ce-doped CsCaCl3 ceramics, Ce4+ ions were observed as hole trap centers. Only Ce-doped CsCaCl3 had charge-compensating defects, which contributed toward TSL glow curves. In all the samples, retrapping electrons or holes was observed and Ce-doped CsCaCl3 was considered to have the highest retrapping efficiency. In addition, the trapped electrons or holes in Eu-doped CsCaCl3 ceramics are more stabilized than those in undoped and Ce-doped CsCaCl3 ceramics.