Structural and optical properties of Cr3+ doped SiO2 nanophosphor

Abstract

SiO2:x% Cr3+ (0 ≤ x ≤ 8) nanopowder samples were synthesized using the sol-gel method. The effect of Cr3+ doping concentration on the SiO2 nanoparticles was studied for possible application in light-emitting diodes (LEDs). Structure and optical properties of undoped and Cr3+ doped SiO2 nanoparticles were investigated in detail. X-ray diffraction (XRD) results confirmed the amorphous phase for undoped SiO2 (A-SiO2) nanopowder. However, above 0.8% Cr3+ there were secondary peaks due rhombohedral structure of chromium (III) oxide (R-Cr2O3). Ultraviolet-visible spectroscopy (UV-Vis) spectra showed a reflectance peak at around 320 nm for the undoped sample. The results showed that when the concentration of Cr3+ is increased there was an emergence of reflectance peaks at around 309, 419, and 553 nm which were attributed to the presence of the Cr2O3 lattices. The photoluminescence (PL) results revealed that with an increase in the amount of Cr3+, the maximum peaks in blue and near red emerge at around 2.82 and 1.89 eV, respectively. Those peaks may be due to defects within both SiO2 and R-Cr2O3. The emission peaks of undoped and Cr3+ doped SiO2 match well with the Uv-vis results. The international illumination colour chromaticity showed that above 0.8% Cr3+ the colour shifts from yellow to blue with an increase in Cr3+ concentration. The investigation indicated that Cr3+ doped SiO2 have a potential application in blue and yellow LED chips for lighting.