Design, synthesis and characterization of a new apatite phosphor Sr_4La_2Ca_4(PO_4)_6O_2:Ce^3+ with long wavelength Ce^3+ emission

A new apatite phosphor Sr4La2Ca4(PO4)(6)O-2:Ce3+ with bright long wavelength emission was synthesized by solid state reaction. The crystal structure and its photoluminescence properties were studied through X-ray diffraction refinement, excitation and emission spectra. Sr4La2Ca4(PO4)(6)O-2:Ce3+ phosphor can be effectively excited by UV light and emit intense green emission band at 506 nm due to the 5d-4f transitions of Ce3+. The concentration quenching as well as thermal quenching properties were also investigated in detail and were compared with the commercial green phosphor (LMS520B). In addition, a white LED lamp was fabricated by combining the optimized green-emitting Sr4La2Ca4(PO4)(6)O-2:Ce3+ and the commercial red phosphor (ZYP630) with a GaN chip (365 similar to 370 nm). The Commission International de l'Eclairage (CIE) chromaticity coordinates, correlated color temperature (CCT) and color-rendering index (CRI) were found to be (0.347, 0.340), 4868 K and 84.6, respectively, and the luminous efficacy is measured to be 30.63 lm/W at room temperature with a forward-bias current of 200mA.