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Photoluminescence of ceramic Ba2Mg(PO4)2: Ce/Mn/Na/Sr phosphor: Site occupation, energy transfer, charge compensation, and alkaline-earth-metal-ions blending study
The phosphor-converted white light-emitting diodes (pc-wLEDs) are current research hotspot. To meet simultaneously the requirements of high chemical/thermal stability and color-rendering index (CRI), low correlated color temperature (CCT) for actual application is still not be perfectly achieved. Herein, we studied for the first time the incorporation of Ce3+ (blue-emitting) and Mn2+ (orange/red emission) into the dibarium magnesium phosphate ceramic (Ba2Mg(PO4)2, BMP) for packaging of pc-wLEDs via remote ‘capping’ approach, which exhibits highly efficient color-tunable photoluminescence (PL) with splendid chemical/thermal stability, single-phase/full-color-PL, efficient energy transfer (ET). To reduce the impact of heterovalent substitution (Ba2+ ← Ce3+), the monovalent (Li+, Na+, K+) ion, respectively tridoped in BMP: Ce/Mn and played both roles as flux and charge compensator, were also studied/compared on the basis of PL efficiency, where Na+ is the most effective because of the lowest electronegativity mismatch between the Ba2+ and Na+. An alkaline-earth-metal-ion blending strategy via partial replacement of Ba2+ with Sr2+ was implemented to further regulate PL and obtain better parameters of CCT/CRI due to the variations of crystal field splitting. The site occupations of Ce/Na/Sr in Ba sites (CN = 8 and 7) and Mn in Mg site (CN = 6) were based on the comparisons of ion radius and confirmed by XRD/Rietveld analyses, where Ce/Na/Sr ions gave priority to occupy the Ba site with CN = 8 due to their much closer ion radius. Altogether, the stably composition-optimized BMP: Ce/Mn/Na/Sr has great potential application as a single-component color-tunable phosphor in n-UV pumped pc-wLEDs.
The pc-wLED fabricated via remote ‘capping’ approach by combination of a n-UV chip with BMP: Ce/Mn/Na/Sr phosphor through Ce to Mn ET with the help of charge compensator of Na and the alkaline-earth-metal-ions blending by Ba/Sr replacement. [Display omitted]
•Ce/Sr/Na occupied at Ba sites while Mn sited in Mg sites.•ET occurs efficiently from Ce to Mn.•Na + acts as charge balancer to improve PL efficiency.•Replacing partial Ba by Sr could regulate PL and improve ET efficiency.•pc-wLED via ‘n-UV LED + white-emitting BMP: Ce/Mn/Na/Sr’ is achieved.