Optimizing Cr3+ concentration and evaluating energy transfer from Cr3+ to Nd3+ in Cr,Nd:GGG nanocrystals prepared by sol-gel method

Nanopowder of Cr:GGG and nanopowder of Cr,Nd:GGG with different concentrations of Cr3+ ranging from 0.1 at.% to 1.5 at.% were synthesized by the sol-gel method using acetic acid and ethylene glycol. Thermal gravimetric analysis and differential scanning calorimetry (TGA-DSC), X- ray diffraction (XRD) and photoluminescence spectroscopy were used to characterize the powder. The crystallite size was about 58 nm when treated at 1000 degrees C for 2 h. Cr3+ photoluminescence spectrum in GGG showed a broad band emission around 730 nm. The intensity of this band decreased when co-doped with Nd, indicating an efficient energy transfer from Cr3+ to Nd3+. Photoluminescence intensity of Nd in Cr,Nd:GGG at 1.06 mu m showed that the optimum concentration of Cr3+ was about 1 at.% (more or less) for 1 at.% Nd3+. This result was also confirmed by chromium fluorescence decay rate analysis. Energy transfer efficiency was found to be about 84% for 1 at.% concentration of each chromium and neodymium.