Single-Site Mn2+-Activated and Sr-Alloyed Ca3(PO4)2 Red Phosphors and Their Lighting Applications
The phosphor-converted white light-emitting diode (WLED) has received tremendous attention as a promising alternative to traditional light sources in lighting and displays. Herein, a novel broadband red emitter Ca 2 Sr(PO 4 ) 2 :Mn 2+ was successfully designed and synthesized based on the Sr-alloying and Mn-doping of Ca 3 (PO 4 ) 2 . The phase purity of the materials was verified by x-ray diffraction (XRD) analyses, while a scanning electron microscope (SEM) coupled with an energy-dispersive spectrometer (EDS) was employed to confirm the uniform dopant distribution. XRD Rietveld refinements were further performed to clarify the site occupation of alloying Sr and the Mn dopants. Effective site engineering confined the Mn dopants in a highly symmetric Ca5 site and excluded the immersion of Sr, leading to an extraordinarily long fluorescence lifetime. Density functional theory (DFT) simulations also revealed the good potential of the materials as host matrices for activators such as Mn 2+ . Finally, Ca 2 Sr(PO 4 ) 2 :Mn 2+ was used to fabricate a WLED prototype based on a near-ultraviolet (n-UV) commercial LED chip, which realized a warm white-light emission and high color rendering index (Ra) of 82.9. This WLED was able to survive the long-term stability test while maintaining high luminous efficacy of ~ 60 lm/W within 20 h, showing its great potential in practical applications.
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