Facile combustion synthesis of (Y,Pr)${}_2$O${}_3$ red phosphor. Study of luminescence dependence on dopant concentration and enhancement by the effect of co-dopant

There occurs a great interest in explaining the dependence of dopant concentration on the luminescence efficiency of rare earth oxides. Unambiguously, this study explains that luminescence intensity increases with increase in dopant concentration only up to optimised value. The syntheses of doped and co-doped yttrium oxide (Y${}_2$O${}_3$) nanophosphors in this study were carried out by making use of combustion method. This method produces the nanophosphors that have sizes ranging between 5 and 20 nm as confirmed by transmission electron microscopy. X-ray diffraction pattern confirms that the incorporation of praseodymium oxide (Pr${}^{3+}$) and gadolinium oxide (Gd${}^{3+}$) does not cause any change in the cubic structure of Y${}_2$O${}_3$. The phase purity has been confirmed by Fourier transform infrared spectrum. Diffuse reflectance spectra reveal that the bandgap increases with increase in annealing temperature. Bandgap has been calculated by making use of the Kubelka–Munk function. Strongest emission was observed at 605 nm with 2 wt% of Pr${}^{3+}$ as optimised concentration. Replacement of Y${}^{3+}$ by Gd${}^{3+}$ partially enhances the 605-nm emission linearly. The [Y:Pr:Gd] exhibits luminescence intensity of 2.705 times more than that of Y:Pr nanophosphors. This is for the first time our team has made a detailed study regarding the effects of co-doping in the case of Y${}_2$O${}_3$:Pr powders. We have successfully presented the changes that happen to the particle after co-doping especially in the particle size and luminescence properties.