Defect states and temperature stability of Eu2+ center in Eu-doped yttrium aluminum garnet

Creating Deep Traps in Yttrium Aluminum Garnet for Long‐Term Optical Storage and Afterglow‐Intensity‐Ratio‐Based Temperature Sensing

“…Based on the observed creation of trap 3 and trap 4 and remarkable enhancement of trap 2 in the presence of Eu 2+ in the as‐made sample, trap 2, 3, and 4 are likely related to complex defects containing oxygen vacancies and adjacent Eu 2+ on Y 3+ site for charge compensation. [ 28,29 ] The remaining trap 2 after air annealing may contains Eu 3+ that is considered as electron trap. [ 27 ]…”

“…It is worth noting that Eu 2+ is created in the as-made YAG:Tb,Eu and shows a emission band peaked at 440 nm (see Figure 1c), consistent with that observed in YAG:Eu 2+ . [28,29] One can see that the Eu 2+ emission disappears after the annealing (see Figure 1c), while the Eu 3+ characteristic emissions are enhanced significantly (see Figure 1d), indicating conversion of Eu 2+ to Eu 3+ , which is also supported by the diffuse reflectance spectra (see Figure 1e) that show the disappearance of Eu 2+ 4f 7 →4f 6 5d 1 absorption in the range of 300-430 nm and the increase of the Eu 3+ -O 2− charge transfer (CT) absorption band in the range of 225-270 nm after annealing. The remarkable reduction of trap 1 and trap 2 and disappearance of trap 3 and trap 4 after annealing (see Figure 1b) suggest that these traps are related to oxygen vacancies because the as-made sample may contain oxygen vacancies due to sintering in reducing atmosphere.…”

“…Based on the observed creation of trap 3 and trap 4 and remarkable enhancement of trap 2 in the presence of Eu 2+ in the as-made sample, trap 2, 3, and 4 are likely related to complex defects containing oxygen vacancies and adjacent Eu 2+ on Y 3+ site for charge compensation. [28,29] The remaining trap 2 after air annealing may contains Eu 3+ that is considered as electron trap. [27] The presence of oxygen vacancies in the as-made YAG:Tb,Eu is supported by the experimental phenomenon that both the TL glow peaks of trap 1 and trap 2 shift toward higher temperatures after annealing (see Figure 1b).…”