A novel red-emitting La2CaHfO6:Mn4+ phosphor based on double perovskite structure for pc-WLEDs lighting

Xing, Gongcheng; Feng, Yuxin; Gao, Zhiyu; Tao, Mengxuan; Wang, Hongquan; Wei, Yi; Molokeev, Maxim S.; Li, Guogang Source: CRYSTENGCOMM, 21 (23):3605-3612; 10.1039/c9ce00556k JUN 21 2019

Non-rare earth doped oxides with red emission are one of the current research hotspots for achieving the warm white light range in the phosphor converted white light emitting diodes (pc-WLEDs) field. In the current work, a novel Mn4+-activated La2CaHfO6 red phosphor is reported for the first time and its crystal structure is analyzed by Rietveld refinement. The photoluminescent properties of La2CaHfO6:Mn4+ are investigated in detail with the help of diffuse refletance spectroscopy, photoluminescence spectroscopy, and temperature-dependent PL spectroscopy. Based on the 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+ displays intense red emission centered at 693 nm. Through an accurate calculation of Dq/B (2.47) and nephelauxetic effect β1 (0.949), the origination of strong crystal field (CF) and deep-red emission is demonstrated. By combining the 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 the as-prepared La2CaHfO6:Mn4+ phosphors can be used as red-emitting candidate in pc-WLEDs lighting.