VUV-UV photoluminescence, site occupancy and thermal stability of blue-emitting K_2CaP_2O_7:Eu~(2+) UV-LED phosphor

摘要

Blue-emitting phosphors K_2Ca_(1-x)P_2O_7:xEu~(2+) (x = 0.005; 0.010; 0.015) were prepared by a solid-state reaction. The luminescence properties of the phosphors were systematically investigated. VUV photoluminescence spectra of K_2Ca(1-x)-P_2O_7:xEu~(2+) exhibit that three distinct bands peaking at 439, 478 and 535 nm can be attributed to the overlap of Eu(1), Eu(2) and Eu(3) emission bands, which are ascribed to the 4f-5d transition of Eu~(2+). The critical quenching concentration of Eu~(2+) in K_2CaP_2O_7 phosphor is about 1 mol%, and the critical transfer distance was determined to be 32.23 A. When the temperature turned up to 150 °C, the emission intensity of K_2Ca_(0.99)P_2O_7:0.01Eu~(2+) sample was 60% of the initial value at room temperature. The activation energy E_a was calculated to be 0.217 eV, which proved the good thermal stability of the phosphor. All the properties indicated that the K_2CaP_2O_7:Eu~(2+) is promising blue-emitting phosphor for application in LED-based lighting or display systems.