A novel dazzling Eu3+-doped whitlockite-type phosphate red-emitting phosphor for white light-emitting diodes

A series of novel red-emitting Ca8ZnLa1-xEux(PO4)(7) phosphors were successfully synthesized using the high-temperature solid-state reaction method. The crystal structure, photoluminescence spectra, thermal stability, and quantum efficiency of the phosphors were investigated as a function of Eu3+ concentration. Detailed analysis of their structural properties revealed that all the phosphors could be assigned as whitlockite-type -Ca-3(PO4)(2) structures. Both the PL emission spectra and decay curves suggest that emission intensity is largely dependent on Eu3+ concentration, with no quenching as the Eu3+ concentration approaches 100%. A dominant red emission band centered at 611nm indicates that Eu3+ occupies a low symmetry sites within the Ca8ZnLa(PO4)(7) host lattice, which was confirm by Judd-Ofelt theory. Ca8ZnLa1-xEux(PO4)(7) phosphors exhibited good color coordinates (0.6516, 0.3480), high color purity (similar to 96.3%), and high quantum efficiency (similar to 78%). Temperature-dependent emission spectra showed that the phosphors possessed good thermal stability. A white light-emitting diode (LED) device were fabricated by integrating a mixture of obtained phosphors, commercial green-emitting and blue-emitting phosphors into a near-ultraviolet LED chip. The fabricated white LED device emits glaring white light with high color rendering index (83.9) and proper correlated color temperature (5570K). These results demonstrate that the Ca8ZnLa1-xEux(PO4)(7) phosphors are a promising candidate for solid-state lighting.