Crystal structure, photoluminescence properties and thermal stability of BaLu2Si3O10:Eu3+ red-emitting phosphors with high color purity for near-UV-excited white LEDs

Abstract

A series of BaLu2-xEuxSi3O10 (x = 0.1, 0.5, 0.6, 0.7, 0.9 and 1.0) red-emitting phosphors were synthesized via a high-temperature solid-state reaction. The Rietveld refinement results revealed that BaLu1.3Eu0.7Si3O10 phosphor possess a monoclinic system with space group P21/m (no.11). Upon excitation at 395 nm, the Eu3+ ions activated BaLu2Si3O10 phosphors exhibited a strong red emission centered at 610 nm due to the 5D0→7F2 transition. The critical doping concentration of Eu3+ ion was x = 0.7 and the critical distance of Eu3+ ions in BaLu2Si3O10 phosphor was determined as 8.35 Å. The energy transfer among Eu3+ ions in BaLu2Si3O10 phosphor was found to be a dipole-dipole interaction. Additionally, the BaLu1.3Eu0.7Si3O10 phosphor exhibited a good thermal stability and the activation energy (ΔE) was estimated to be 0.18 eV. The internal and external quantum efficiency of BaLu1.3Eu0.7Si3O10 phosphor was measured to be 83.2% and 8.85%, respectively. In addition, a white light-emitting diode (WLED) device was fabricated by incorporating a 395 nm near-ultraviolet chip with an optimized red-emitting BaLu1.3Eu0.7Si3O10 phosphor, commercial blue emitting BaMgA10O17:Eu2+, and green emitting (Ba,Sr)2SiO4:Eu2+ phosphors. Under an applied forward-bias current of 20 mA, the fabricated WLED device exhibited the spectral properties of CIE color coordinates (0.3766, 0.3789), correlated color temperature (4122 K), and high color rendering index (88.8). All the results demonstrate that BaLu1.3Eu0.7Si3O10 can act as a potential red phosphor for application in near-ultraviolet excited WLEDs.