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Issue 14, 2019
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Protected-annealing regulated defects to improve optical properties and luminescence performance of Ce:YAG transparent ceramics for white LEDs

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Abstract

Ce:YAG transparent ceramic, a promising photo-converter for white LED lighting, faces a significant obstacle of post-annealing treatments, which allow the simultaneous elimination of defections and the regulation of the redox state of Ce. In this paper, vacuum as-sintered high quality Ce:YAG ceramics were subjected to various annealing conditions, and their microstructural evolution, and optical and luminescence properties were monitored and studied systematically. The results showed that air annealing efficiently benefited the microstructure and optical transmittance. In addition, 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). By constructing with 1350 °C air annealed Ce:YAG ceramics, a high-performance white LED with a luminous efficiency radiation (LER) exceeding 220 lm W−1 was achieved, thanks to the “protected”-annealing condition, which guaranteed moderate CT from Ce(IV) to Ce(III) due to weakened pump light absorption by defects. Differing from traditional Ce:YAG phosphors, excrescent oxygen vacancies were introduced by annealing Ce:YAG ceramics in hydrogen, leading to deteriorated luminescence properties. Therefore, it is expected that this refined preparation of Ce:YAG photo-convertors could drive the development of white LED lighting.

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

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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, 2019,7, 4057-4065

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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, 7, 4057
    DOI: 10.1039/C8TC06600K

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