期刊
JOURNAL OF ALLOYS AND COMPOUNDS
卷 786, 期 -, 页码 808-816出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jallcom.2019.01.340
关键词
Ca3Al2Ge3O12 garnet phosphor; Melamine as reducing agent; Photoluminescence; Ce -> Mn energy transfer; Phosphor for w-LED; Cluster luminescence
资金
- European Regional Development Fund within the Innovative Economy Operational Programme [POIG.01.01.02-02-006/09]
Ca3Al2Ge3O12 phosphors, singly doped with Ce(3+ )and co-doped with Mn2+, were synthesized by the solid-state reaction in ammonia atmosphere at 1200 degrees C using Li2CO3 as a flux. The band gap energy of the host was determined to be 3.7 eV. In these phosphors, Ce3+ ions exclusively occupy the Ca2+ site, while Mn2+ ions occupy both the Ca2+ and Al3+ sites. Under 420 nm excitation, the Ce3+:Ca3Al2Ge3O12 phosphor emits bluish-green light from Ce3+ (470 nm) with a Stokes shift established at 2280 cm(-1). The Ce3+/Mn2+:Ca3Al2Ge3O12 phosphor excited at 420 nm emits orange light (580 nm) from Mn2+ in the Ca2+ site due to the Ce3+-> Mn-2(+) energy transfer almost exclusively to this site. Ce3+ emission in the co-doped phosphor is very weak, even for relatively small concentrations (1%) of Mn2+. For Mn2+ concentration of 5% it disappears almost completely. Luminescence quantum yields of these phosphors amount to 24% and 20% in the case of Ce3+:Ca3Al2Ge3O12 and Ce3+/Mn2+:Ca3Al2Ge3O12, respectively. The critical distance for Ce3+ -> Mn2+ energy transfer was calculated to be 6.2 A and the efficiency of the energy transfer was estimated as 88%. These parameters suggest a non-uniform distribution of doped ions and the formation of Ce-Mn clusters. (C) 2019 Elsevier B.V. All rights reserved.
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