Synthesis and Characterization of Ce3+:YAG Phosphors by Heterogeneous Precipitation Using Different Alumina Sources |
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Authors: | Sea-Fue Wang K. Koteswara Rao Yu-Chuan Wu Yuh-Ruey Wang Yung-Fu Hsu Chian-You Huang |
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Affiliation: | Department of Materials and Mineral Resources Engineering, National Taipei University of Technology, Taipei, Taiwan, R.O.C. |
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Abstract: | Ce3+-doped yttrium aluminum garnet (Ce:YAG) phosphor powders were synthesized by heterogeneous precipitation process using three different aluminum sources: α-phase, θ-phase, and boehmite (AlOOH). Mixtures of yttrium and cerium nitrate solutions containing various aluminum sources were precipitated by ammonia solution in normal and reverse strike methods. The influence of pH was studied in the normal strike method by maintaining the solutions at pH 7, 9, and 11 during precipitation. Dried precipitates were double calcined at 1300°C/16 h and 1300–1500°C/24 h, at a ramping rate of 10°C/min, with an intermittent wet ball milling in water. Structural evolution of the resultant phosphors was studied by powder XRD. In the normal strike method, a highly pure YAG phase was formed by α- alumina (pH 7, 11) and θ-alumina (pH 11) while boehmite source ended up with mixed phases of YAlO3 (YAP) and Y4Al2O9 (YAM) along with YAG phase at all pH values of precipitation. However, in the reverse strike process, the θ-phase of alumina gave an extremely pure Ce:YAG phase at a relatively lower calcination temperature (1400°C/24 h) compared with the α-phase and also showed more intense emission of yellowish-green light under blue (λ=469 nm) excitation. Scanning electron microscopy revealed 1–2 μm sized particles with least agglomeration in the reverse strike method. |
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