A Novel Red-Emitting La2CaHfO6:Mn4+ Phosphor Based on Double Perovskite Structure for pc-WLEDs Lighting
Non-rare earth doped oxides with red emission is one of current reasearch hotspot for achieving warm white gamut in the phosphor converted white light emitting diodes (pc-WLEDs) lighting filed. In the current work, a novel Mn4+-activated La2CaHfO6 red phosphor is firstly reported and its crystal structure is analyzed by Rietveld refinement. The photoluminescent properties of La2CaHfO6:Mn4+ are investaged in detail with the diffuse refletance spectra, photoluminescence spectra and temperature-dependent PL sprctra. Based on diffuse refletance spectra, the calculated optical band gap for La2CaHfO6 is 4.9 eV, indicating that La2CaHfO6 could be a suitable host for activators doping. Under 380 nm near-ultraviolet (n-UV) light excitation, the as-prepared La2CaHfO6:Mn4+ display intense red emission centered at 693 nm. Through an accurate calculation of Dq/B (2.42) and nephelauxetic effect 1 (0.949), it demonstrates that the origination of strong crystal filed (CF) and deep-red emission. By combining representative La2CaHfO6:0.002Mn4+, blue BAM:Eu2+ and green (Ba,Sr)2SiO4:Eu2+ phosphors with a 380 nm UV chip to fabricate the pc-WLEDs device, a white light is obtained with low correlated color temperature (CCT = 5165 K) and high color rendering index (Ra = 87.8), demonstrating that as-prepared La2CaHfO6:Mn4+ phosphors can be red-emitting candidate in pc-WLEDs lighting.