Double perovskite Ca₂LuTaO₆:Eu³⁺ red-emitting phosphors: Synthesis, structure and photoluminescence characteristics

A series of novel high-brightness double perovskite tantalate Eu³⁺-activated Ca₂LuTaO₆ (CLT) red-emitting phosphors with high thermal stability were successfully synthesized by a high-temperature solid-state method. X-ray diffraction (XRD), emission and excitation spectra, decay curves, temperature-dependent photoluminescence spectra, CIE chromaticity coordinates, as well as internal quantum efficiency (IQE) were used to analyze these phosphor samples. Under 396 nm excitation, the CLT:Eu³⁺ phosphors gave brilliant red emission peaking around 616 nm due to the ⁵D₀→⁷F₂ transition of Eu³⁺ ions. The optimal Eu³⁺ doping concentration was 40 mol%, and moreover, the critical distance (R_c) and θ were 8.55 Å and 5.01, respectively. Thus, the dipole-dipole interaction may be responsible for the energy transfer mechanism of Eu³⁺ activators in the CLT:Eu³⁺ phosphors. In addition, the color purity of CLT:0.4Eu³⁺ sample was calculated to be 95.8% and its IQE was found to be as high as 74%. Impressively, the integrated emission intensity of CLT:0.4Eu³⁺ was about 3.79 times higher than that of commercial Y₂O₃:Eu³⁺ red phosphors under 396 nm excitation. More importantly, the CLT:0.4Eu³⁺ sample exhibited excellent thermal stability. Therefore, these superior luminescence properties of CLT:Eu³⁺ phosphors demonstrated their potential applications in white light-emitting diodes (WLEDs) as red color converters.