Effect of annealing environment on the luminescence and structural properties of pure CePO4 and Tb: CePO4 nanowires

We present a detailed study on post synthesis annealing effects on luminescence as well as electronic and structural properties of pure and Terbium doped (5 wt%) CePO4 nanowires (NWs) prepared using green synthesis chemical route. The formation of nanowire was confirmed from transmission electron microscopy and small angle X-ray scattering measurements, revealing elongated nanowire shape with monoclinic crystal structure in agreement with X-ray diffraction observations. Photoelectron spectroscopy data analysis showed that samples annealed under air consist of only Ce4+ oxidation state, while those annealed under N2 environment showed the presence of mixed Ce4+ and Ce3+ oxidation states. However, this Ce4+ oxidation state has not propagated inside the bulk of NWs as seen from X-ray absorption spectra around Ce LIII absorption edge. The photoluminescence measurements revealed significant differences between the samples annealed in air and N2 flow respectively. Post synthesis annealing under N2 flow helped to suppress the contribution of Ce4+ oxidation state in photoluminescence. The overall results are beneficial from the luminescent device point of view and form a basis for advance studies.