Color-Tunable Luminescence and Energy Transfer Properties of Ca9Mg(PO4)6F2:Eu2+, Mn2+ Phosphors for UV-LEDs

• Published in: Journal of physical chemistry. C Vol. 118; no. 20; pp. 11026 - 11034
• Main Authors: Li, Kai, Geng, Dongling, Shang, Mengmeng, Zhang, Yang, Lian, Hongzhou, Lin, Jun
• Format: Journal Article
• Language: English; Japanese
• Published: American Chemical Society 22.05.2014
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp501949m

Eu2+-, Mn2+-activated Ca9Mg(PO4)6F2 (CMPF) phosphors with blue to yellow color-tunable emission properties have been synthesized via high-temperature solid-state reaction method. The crystal structure of Ca9Mg(PO4)6F2 has been identified by Rietveld refinement. The different crystallographic sites of Eu2+ in CMPF:Eu2+ phosphors have been confirmed by virtue of their fluorescence decay lifetimes. The Eu2+-activated CMPF phosphors exhibit broad excitation spectra from 200 to 420 nm (which matches well with the UV-based LED chips) and emission spectra from 380 to 580 nm centered at 454 nm. Energy transfer from Eu2+ to Mn2+ ions in Eu2+, Mn2+codoped CMPF samples is possible because of the spectral overlap between Eu2+ emission and Mn2+ excitation spectra, and the constant fall of fluorescence decay lifetimes of Eu2+ ion with increasing Mn2+ concentration demonstrates the occurrence of it, which provides the color-tunable emission from blue to yellow through adjusting Mn2+ concentration. The energy transfer mechanism between Eu2+ and Mn2+ ions is verified to be electric dipole–quadrupole interaction by analyzing the experimental results. The critical distance between them calculated by concentration quenching (14.57 Å) and spectral overlap methods (14.90 Å) are consistent, which testifies the energy transfer mechanism above from Eu2+ to Mn2+ is appropriate. These results show CMPF:Eu2+, Mn2+ phosphors could be anticipated for UV-pumped white-light-emitting diodes (wLEDs).