In this study, red-emitting AlPO4:Cr3+ phosphors have been successfully synthesized by a facile sol-gel method. The Tanabe–Sugano diagram demonstrates that the surrounding sites of Cr3+ ions has a high crystal field with Dq/B=2.47. The sharp 694-nm peak on the PL of AlPO4:Cr3+ phosphor could be attributed to the 2E→4A2 electron transition of Cr3+ ions. The AlPO4:0.3%Cr3+ phosphor presents the highest PL intensity, then a purple LED prototype is obtained by coating the optimum powder on a UV LED

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... chip. The color coordinates (0.2412, 0.1330) of the purple LED prototype implies that AlPO4:Cr3+ phosphors are promosing to be used as deep red phosphor powder for horticulture LED lighting.