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Protected-annealing regulated defects to improve optical properties and luminescence performance of Ce:YAG transparent ceramics for white LEDs

Abstract

Ce:YAG transparent ceramic, a promising photo-converter for white LED lighting, is facing a significant obstacle of post-annealing treatments, which allows simultaneous regulation of redox state of Ce ions and the elimination of defects. In this paper, the vacuum as-sintered highly quality Ce:YAG ceramics were subjected to various annealing conditions, and their microstructural evolution, optical and luminescence properties were monitored and studied systematically. The results showed air annealing efficiently benefited the microstructure and optical transmission. Additionally, the absorption band below 300 nm was strongly dependent on the annealing strategies due to the elimination of defects (e.g. F/F+-type color centers) and charge transfer (CT) between Ce(III) and Ce(IV). Constructing with 1350 oC air annealed Ce:YAG ceramics, a high-performance white LED with quantum efficiency of 73.5% was attained, thanks to the protected annealing condition, that involves weakened pump light absorption by defects and moderate CT from Ce(IV) to Ce(III). Differing from traditional Ce:YAG phosphors, the excrescent oxygen vacancies were introduced by annealing Ce:YAG ceramics in hydrogen, leading to their deteriorated luminescence properties. Therefore, it is expected that this refined preparation of Ce:YAG photo-convertor could drive the development of white LEDs lighting.

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Publication details

The article was received on 29 Dec 2018, accepted on 03 Feb 2019 and first published on 05 Feb 2019


Article type: Paper
DOI: 10.1039/C8TC06600K
Citation: J. Mater. Chem. C, 2019, Accepted Manuscript

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    Protected-annealing regulated defects to improve optical properties and luminescence performance of Ce:YAG transparent ceramics for white LEDs

    B. Sun, L. Zhang, T. Zhou, C. Shao, L. Zhang, Y. Ma, Q. Yao, Z. Jiang, F. A. Selim and H. Chen, J. Mater. Chem. C, 2019, Accepted Manuscript , DOI: 10.1039/C8TC06600K

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