Substitution priority of Eu2+ in multi-cation compound Sr0.8Ca0.2Al2Si2O8 and energy transfer**Project supported by the National Natural Science Foundation of China (Grant Nos. 51672066 and 50902042), Funds for Distinguished Young Scientists of Hebei Province, China (Grant No. A2015201129), and Personnel Training Project of Hebei Province, China (Grant No. A2016002013).

Abstract

A blue phosphor was obtained by doping Eu2+ into a multi-cation host Sr0.8Ca0.2Al2Si2O8 through high temperature solid state reaction. The emission spectra show a continuous red-shift behavior from 413 nm to 435 nm with Eu2+ concentration increasing. The substitution priority of Eu2+ in Sr0.8Ca0.2Al2Si2O8 was investigated via x-ray diffraction (XRD) and temperature properties in detail: the Ca2+ ions are preferentially substituted by Eu2+at lower doping, and with the Eu2+ concentration increasing, the probability of substitution for Sr2+ is greater than that of replacing Ca2+. Accordingly, we propose the underlying method of thermal property to determine the substitution of Eu2+ in the multi-cation hosts. Moreover, the abnormal increase of emission intensity with increasing temperature was studied by the thermoluminescence spectra. The energy transfer mechanism between the Eu2+ ions occupying different cation sites was studied by the lifetime decay curves. A series of warm white light emitting diodes were successfully fabricated using the blue phosphors Sr0.8Ca0.2Al2Si2O8: Eu2+ with commercial red phosphor (Ca Sr)SiAlN3: Eu2+ and green phosphor (Y Lu)3Al5O12: Ce3+, and the luminescent efficiency can reach 45 lm/W.