A Cerium Doped Scandate Broad Orange-Red Emission Phosphor and its Energy Transfer-Dependent Concentration and Thermal Quenching Character.

Abstract

A series of BaSr2Sc4O9 and Ce3+-doped BaSr2Sc4O9 phosphors were synthesized via the high temperature solid state reaction. Crystal structure information on BaSr2Sc4O9 is first refined using the Rietveld method based on the XRD data, and it is assigned to the trigonal system with the R3 space-group. The photoluminescence properties were investigated in detail, including the emission and excitation spectra, site occupation, decay lifetime, thermal quenching, and quantum efficiency. There are three Ba2+/Sr2+ sites and four Sc3+ sites in this structure. The Ce3+ ions in the 6-fold coordinated Sr2+/Ba2+ sites show a near-ultraviolet-blue emission with a peak at around 407 nm under ultraviolet excitation. The Ce3+ ions in Sc3+ sites exhibit a bright broad orange-red emission with the peak at around 615 nm under near-ultraviolet and blue excitation. The energy transfer process between the different sites is demonstrated based on the spectral analysis, theoretical calculation, and decay lifetime variation. Under excitation of 345 nm, the energy transfer phenomenon and distribution of activator ions lead to the invalidation of part of the Ce3+ ions, and then it causes a higher concentration quenching point. The participation of the energy transfer in the thermal quenching phenomenon causes the abnormal intensity variation, which is ascribed to the energy compensation by the increasing energy transfer efficiency at high temperature. The internal quantum efficiency is 45% under the 420 nm excitation wavelength. An excellent white light emitting diode lamp is obtained by fabricating BaSr2Sc4O9:Ce3+ with BAM:Eu2+, β-sialon:Eu2+, and a 395 nm GaN chip; its CIE coordinate ( x, y), CCT, and Ra are (0.3708, 3463), 4023 K, and 84. These results reveal the correlation between energy transfer and luminescent property and provide a practical foundation to comprehend and adjust the photoluminescence performance.