Tunable emission with excellent thermal stability in single-phased SrY2O4:Bi3+,Eu3+ phosphors for UV-LEDs

Highlights: • Novel phosphors SrY₂O₄:Bi³⁺,Eu³⁺ with tunable emitting from blue to red were synthesized. • Highly efficient energy transfer (ET) from Bi³⁺ to Eu³⁺ was obtained before concentration quenching. • Excellent thermal stability was determined, which is superior to that of most recently reported Bi³⁺,Eu³⁺ co-doped phosphors. Novel single-phased phosphors SrY₂O₄:Bi³⁺,Eu³⁺ (SYO:Bi³⁺,Eu³⁺) with tunable emitting were successfully synthesized by the conventional solid-state method. X-ray diffraction, excitation and emission spectra, decay curves as well as temperature-dependent luminescence were applied to characterize the as-obtained phosphors. Under ultraviolet (UV) excitation, blue luminescence centered at 410 nm was found in SYO:Bi³⁺. By introducing Eu³⁺ into SYO:Bi³⁺, highly efficient energy transfer (ET) process with ET efficiency of 92.65% from Bi³⁺ to Eu³⁺ was obtained before concentration quenching. The possible ET mechanism from Bi³⁺ to Eu³⁺ were investigated systematically. By altering Eu³⁺ content, tunable emission from blue to red was realized. More importantly, investigation of the thermal stability showed that over 98% of the room-temperature emission intensity was still preserved at 155 °C, which is superior to that of most recently reported Bi³⁺,Eu³⁺ co-doped phosphors. These results indicate that this kind of easy fabrication, low-cost and highly stable SYO:Bi³⁺,Eu³⁺ are potential candidates for blue-red phosphors for application in UV chip based w-LEDs.