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

• Published in: Journal of the American Ceramic Society 2018-09, Vol.101 (9), p.4095-4107
• Main Authors: Li, Li, Tang, Xiaohua, Zheng, Yifei, Wu, Zhaojie, Chang, Wenxuan, Jiang, Sha, Xiang, Guotao, Zhou, Xianju
• Format: Article
• Language: English
• Subjects: Calcium phosphates; Chemical synthesis; Color temperature; Crystal structure; Diodes; Emission spectra; Europium; luminescence; Organic light emitting diodes; phosphor; Phosphors; Photoluminescence; Quantum efficiency; Temperature dependence; Thermal stability; White light; whitlockite‐type phosphate
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/jace.15691

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 β‐Ca3(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 611 nm 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 (~96.3%), and high quantum efficiency (~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 (5570 K). These results demonstrate that the Ca8ZnLa1−xEux(PO4)7 phosphors are a promising candidate for solid‐state lighting. A electroluminescent emission spectrum of the fabricated white LED device under 120 mA operating current (A). Fabricated white LED device (B). Luminescent image of the white LED device under 120 MA operating current (C).