Investigation of UV emission and energy transfer process in Ce3+, Gd3+, Pr3+ and their combination doped nano crystallite La2O3 phosphors

Abstract

Despite being a harmful radiation, there are many useful applications of UV radiation. This includes its use in the biomedical field. Hence, it is required to generate the UV radiation with desired characteristics. In this work, seven rare earth based compounds i. e. 1 % Ce3+: La2O3, 1 % Gd3+: La2O3, 1 % Ce3+ – 1 % Gd3+: La2O3, 2 % Ce3+ – 1 % Gd3+: La2O3, 1 % Pr3+: La2O3, 1 % Pr3+ – 1 % Gd3+: La2O3, and 2 % Pr3+ – 1 % Gd3+: La2O3 have been synthesized to study their UV emission properties and related energy transfer process. The synthesis process is also relatively simple and eco-friendly, with fewer elements used and giving a higher yield of products. The XRD & EDAX analysis reveals that the obtained compounds possess high purity and are in hexagonal phase state with crystallite size in the nanometer range. The bandgap and refractive index were calculated from absorption spectra obtained by UV – Visible spectrometry. From the PL Spectroscopy, the emission of 1 % Gd3+: La2O3 falls in UVB region, while that of 1 % Ce3+: La2O3 & 1 % Pr3+: La2O3 – in UVA region. Both, UVA and UVB emission were recorded in 1 % Ce3+ – 1 % Gd3+: La2O3, 2 % Ce3+ – 1 % Gd3+: La2O3 due to the resonance transfer and radiative transfer of energy from Ce3+ ion to Gd3+ ion. In 1 % Pr3+ – 1 % Gd3+: La2O3 and 2 % Pr3+ – 1 % Gd3+: La2O3, the emission was obtained in UVA with very low intensity and another intense peak was observed in the visible region due to the energy transfer from Gd3+ ion to Pr3+ ion. The parameters like redshift D, centroid shift Ɛc and crystal field splitting Ɛcfs were calculated for Ce & Ce – Gd based La2O3 compounds. Based on these calculations, the model for energy levels of Ce3+ in La2O3 is proposed.

Keywords

• UV emission
• XRD analysis
• EDAX spectra
• UV – Visible analysis
• PL analysis