Study on the photoluminescence properties of a color-tunable Ca9ZnK(PO4)7: Eu3+ phosphor

A series of Eu3+-doped phosphors Ca9(1−x)ZnK(PO4)7: 9xEu3+ (x = 0 - 0.08) have been synthesized by the high temperature solid state method. The X-ray diffraction (XRD) and photoluminescence (PL) were utilized to characterize the phosphors. The phosphors can be effectively excited by near-ultraviolet (NUV) light. The Ca9ZnK(PO4)7 host exhibits broad blue emission band centered at 440 nm, while Ca9ZnK(PO4)7: Eu3+ shows both the blue emission band and the characteristic red emission in the region of 570 - 700 nm. With increasing Eu3+ content, the relative emission intensity of the host at 440 nm decreased remarkably, indicating that energy transfer occurred from the Ca9ZnK(PO4)7 host to Eu3+ ions. The phosphors show tunable color from blue to orange based on energy transfer from the host to Eu3+ ions.