Significantly enhanced luminescence efficiency and thermal stability of BaSi2O2N2:Eu2+ phosphor by doping a very small amount of SiC

Abstract Eu2+-activated BaSi2O2N2 oxonitridosilicate phosphor is an efficient cyan compensator to improve the color rendering index of WLEDs for full-spectrum lighting. However, the low luminescent efficiency and poor thermal stability of this type of phosphor severely restrict its practical industry applications. Herein, SiC was proposed into the preparation process of BaSi2O2N2 to enhance the luminescence and thermal stability. Due to the very small amount of SiC addition, the samples of BaSi2O2N2-4x/3Cx:Eu2+ maintain the orthorhombic crystal structure of BaSi2O2N2:Eu2+, but the unit cell volumes and particle sizes become larger. The luminescent intensity reaches the maximum when x = 0.075 and the absorption efficiency and internal quantum efficiency are 67.59% and 58.26%, which are increased by 5.34% and 14.66% relative to the SiC-free sample, respectively. The bandgap and lifetime of Ba0.97Si2O2N1.9C0.075:0.03Eu2+ are calculated to be 2.06 eV and 407.91 ns, respectively. The sample of Ba0.97Si2O2N1.9C0.075:0.03Eu2+ possesses a higher activation energy of 0.383 eV and exhibits a little loss of 13.3% of luminescence intensity at 423 K, which is improved by 11.4% relative to the SiC-free sample. Higher structural stiffness derived from the partially replacement of Si−N bonds by Si-C is supposed as the main reason of the higher thermal stability. The luminescence of Ba0.97Si2O2N1.9C0.075:0.03Eu2+ degrades only by 4.64% in five thermal cycles, which mainly thanks to the improved antioxidant of Eu2+. The Ba0.97Si2O2N1.9C0.075:0.03Eu2+ sample demonstrates an excellent color stability with a tiny chromaticity shift of ~28.19 × 10-3 ranging from 298 to 423 K. A WLED with the cyan-emitting Ba0.97Si2O2N1.9C0.075:0.03Eu2+ exhibits a full spectrum with CRI of 95.1.