Effects of Ce3+ concentration, beam voltage and current on the cathodoluminescence intensity of SiO2: Pr3+–Ce3+ nanophosphor

Abstract

SiO2:Pr3+–Ce3+ phosphor powders were successfully prepared using a sol–gel process. The concentration of Pr3+ was fixed at 0.2 mol% while that of Ce3+ was varied in the range of 0.2–2 mol%. High resolution transmission electron microscopy (HRTEM) clearly showed nanoclusters of Pr and Ce present in the amorphous SiO2 matrix, field emission scanning electron microscopy (FE-SEM) indicated that SiO2 clustered nanoparticles from 20 to 120 nm were obtained. Si–O–Si asymmetric stretching was measured with Fourier transform-IR (FT-IR) spectroscopy and it was also realized that this band increased with incorporation of the activator ions into the SiO2 matrix. The broad blue emission from the Ce3+ ions attributed to the 5d1–4f1 transition was observed from the SiO2:0.2 mol% Pr3+–1 mol% Ce3+ phosphor. This emission was slightly enhanced compared to that of the singly doped SiO2:1 mol%Ce3+ phosphor. Further investigations were conducted where the CL intensity was measured at different beam voltages and currents from 1 to 5 kV and 8.5 to 30 µA, respectively, in order to study their effects on the CL intensity of SiO2:0.2 mol% Pr3+–1 mol% Ce3+. The electron-beam dissociated the SiO2 and as a result an oxygen-deficient surface dead or non-luminescent layer of SiOx, where x < 2 on the surface, was formed.