Sol-gel processing of Eu3+ doped Li6CaLa2Nb2O12 garnet for efficient and thermally stable red luminescence under near-ultraviolet/blue light excitation

Li6CaLa2Nb2O12 garnet is known as an electrolyte for Li+ -batteries. The sol gel processing of this work yielded a series of phase pure Li6CaLa2(1-x)Nb2O12:xEu(3+) garnet phosphors (LCLNG:xEu; x = 0-0.40) that are efficiently excitable with either near -ultraviolet (NUV, similar to 350-400 nm) or blue (similar to 450-475 nm) light to produce dominantly strong 610 nm red emission. Increasing Eu3+ substitution for La3+ (larger x) led to smaller cell constant and lower symmetry of the (La/Ca)O-8 dodecahedron, as revealed via Rietveld structure refinement, and meanwhile narrower bandgap. The excitation/emission behaviors and high quenching concentration of Eu3+ (x = 0.35) were interpreted for the phosphor series by considering bandgap energy, (La/Ca)O-8 distortion and local arrangement of atoms. The LCLNG:0.35Eu optimal phosphor was analyzed to have absolute quantum yields of similar to 51% (lambda(ex) = 393 nm) and 65% (lambda(ex) = 463 nm), fluorescence lifetime of similar to 0.70 ms and color coordinates of around (0.65, 0.35) at room temperature and to be able to retain as high as similar to 85% of its room -temperature intensity at 423 K for the 610 nm emission. Application of LCLNG:0.35Eu further indicated that this phosphor has the potential to be used in NUV-excited LEDs.