Effects of Ce~(3+) concentration, beam voltage and current on the cathodoluminescence intensity of SiO_2:Pr~(3+)-Ce~(3+) nanophosphor

摘要

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 3d1 -4f 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 ìA, 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.