Reduction of Eu3+ to Eu2+ in NaCaPO4:Eu phosphors prepared in a non-reducing atmosphere

Highlights: → The reduction of Eu3+ to Eu2+ in argon atmosphere was firstly observed in phosphates. → Charge compensation model was adopted to explain this reduction in NaCaPO4 matrix. → The preparation temperature was as low as 850 deg. C. → Temperature dependant emission behavior is better than that of a commercial phosphor. - Abstract: The reduction of Eu3+ to Eu2+ in a non-reducing atmosphere of pure argon gas has been reported for the first time in NaCaPO4 host matrix prepared by using a solid-state reaction. Photoluminescence spectral profiles confirmed the presence of Eu2+ ions in the prepared compound and this reduction has been explained by means of a charge compensation model. The effect of lithium incorporation on the photoluminescence efficiency of the NaCaPO4:Eu2+ phosphors were also studied and explained appropriately for various doping concentrations of lithium ions. The CIE coordinates and temperature dependant luminescence profiles of these phosphors were also discussed in order to investigate their potential applications. Besides analyzing its photoluminescence properties, other significant characterizations like XRD, SEM, TG-DTA, FTIR, Raman spectral profiles have also been studied and these interpretations were documented more clearly.