Tunable photoluminescence and temperature sensing properties of Ce3+, Eu2+ co-doped Ca2-xSrxMgSi2O7 phosphors

A series of Ca2-xSrxMgSi2O7: Ce3+, Eu2+ (x = 0, 0.5, 1, 1.5, 2) phosphors were synthesized on the basis of high temperature solid-state reaction strategy. Its phase composition, optical spectral properties, fluorescence lifetime and temperature sensitivity were investigated in detail. Under excitation at 342 nm, the emission spectra of Ca2MgSi2O7: Ce3+, Eu2+ exhibit a purple emission band (Ce3+ ions) and a green emission band (Eu2+ ions). The emission band of Ce3+ overlaps with the excitation band of Eu2+, indicating that there may be energy transfer (ET) between the two ions. The decreasing fluorescence lifetime of Ce3+ with increasing Eu2+ concentration further proves the existent of ET process in Ca2MgSi2O7: Ce3+, Eu2+ phosphor. In addition, Ca2-xSrxMgSi2O7: Ce3+, Eu2+ solid solution was designed and synthesized by Sr2+ substituting Ca2+. As Sr2+ gradually replaced Ca2+, the blue-shift of Ce3+ and Eu(2+)emission band were caused by the change of crystal field. With the increase of temperature, the fluorescence intensity of Ce3+ and Eu2+ emission bands decreased slowly and rapidly, respectively. Hence, in the Ce3+/Eu2+ co-activated Ca2-xSrxMgSi2O7 phosphor, Ce3+ ions and Eu2+ ions can be used as fluorescence intensity ratio (FIR) signals. The maximum relative sensitivity can reach 2.43% K-1 (at 293 K) under 342 nm excitation. The above results indicate that Ca2-xSrxMgSi2O7: Ce3+, Eu2+ phosphors are potential candidates for optical thermometer materials.