Effects of Ce 3+ concentration, beam voltage and current on the cathodoluminescence intensity of SiO 2:Pr 3+–Ce 3+ nanophosphor

Abstract

SiO 2:Pr 3+–Ce 3+ phosphor powders were successfully prepared using a sol–gel process. The concentration of Pr 3+ was fixed at 0.2 mol% while that of Ce 3+ 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 SiO 2 matrix, field emission scanning electron microscopy (FE-SEM) indicated that SiO 2 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 SiO 2 matrix. The broad blue emission from the Ce 3+ ions attributed to the 5d 1 –4 f 1 transition was observed from the SiO 2:0.2 mol% Pr 3+–1 mol% Ce 3+ phosphor. This emission was slightly enhanced compared to that of the singly doped SiO 2:1 mol%Ce 3+ 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 SiO 2:0.2 mol% Pr 3+–1 mol% Ce 3+. The electron-beam dissociated the SiO 2 and as a result an oxygen-deficient surface dead or non-luminescent layer of SiO x , where x < 2 on the surface, was formed.