Effect of Ambient Temperature on the Emission Spectra of Mg2+- and Ga3+-Doped CaS:Eu2+ Red Phosphors
The photoluminescence spectra of alkaline earth sulfide showed the characteristics of temperature dependence. In this work, Mg2+- and Ga3+-doped CaS:Eu2+ phosphors have been synthesized in the tube atmosphere furnace and the influence of ambient temperature on the emission spectra of Mg2+- and Ga3+-doped CaS:Eu2+ red phosphors was studied. The results showed that with the increment of ambient temperature, the emission intensities of the CaS:Eu2+ phosphors doped with Mg2+ and Ga3+ decreased rapidly, the emission peaks of the samples changed from deep red to red, and the half peak width increased. This is due to the fact that the high temperature makes more excited molecules at higher vibrational levels, and the fluorescence is mainly caused by the high vibrational energy level of the excited state. By configurational coordinate diagram of the luminescence center, it is confirmed that back tunneling from the ground state to the excited state leads to the increased FWHMs and the decreased emission intensities.
The authors are grateful to the financial supports from National Natural Science Foundation of China (NSFC) (51504052, 51701035), the foundations from Chongqing Science and Technology Commission (cstc2016jcyjA0157), Chongqing Special Key Technology Innovation of Key Industries (CSTC2017ZDCY-ZDZXX0006).
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