Luminescence characteristics and Förster resonance energy transfer of Y and Bi codoped Al6Si2O13:Eu red nanophosphors obtained by an energy-saving microwave-assisted synthesis

Abstract

A red luminescent YxAl6-xSi2O13:Eu,Bi nanophosphor was successfully synthesized by a rapid, energy-saving microwave-assisted synthesis. This method significantly reduced synthetic time and energy consumption over previous reports using traditional solid-state methods. The results revealed that the single phase of Al6Si2O13 (mullite) nanocrystals had spherical shapes of 30–60 nm diameters. In addition, the influences of Y3+ and Bi3+ ions on photoluminescent properties of Al6Si2O13:Eu3+ were observed. The emission intensity was improved drastically through dopants of Y3+ and Bi3+ ions and increased up to 2.1-fold, compared to that of undoped Al6Si2O13:Eu3+. The internal quantum efficiency of Y0.15Al5.85Si2O13:0.08Eu3+,0.05Bi3+ phosphor was 72% under an excitation wavelength of 395 nm. These results were attributed to flux effects of Y3+ ions and Y3+ doping reduced opportunities for energy transfer (ET) between Bi3+ ions and enhanced the Förster resonance ET from Bi3+ → Eu3+. The Judd-Ofelt theory was employed to discuss the local site symmetry around Eu3+ ions in Y3+-doped hosts. The optimal nanophosphor of Y0.15Al5.85Si2O13:0.08Eu3+,0.05Bi3+ was excited at 395 nm and monitored at 612 nm, from which the Commission International de I'Eclairage color coordinates of Y0.15Al5.85Si2O13:0.08Eu3+, 0.05Bi3+ phosphor was estimated to be x = 0.61 and y = 0.36 in the deep red region. The obtained phosphor could be expected to find application as a near-ultraviolet convertible phosphor for white light-emitting diodes.