Effects of OH radicals and the silicon network on the lifetime of Eu3+-doped sodium silicate glasses

A set of sodium silicate glass matrices were synthesized to study the influence of Na2O concentration on the optical properties of Eu3+. The samples were characterized by optical absorption (OA), time and energy resolved photoluminescence and Fourier Transform Infrared (FTIR). We observed that decreasing sodium oxide concentration affects the absorption of OH radicals in the host matrix. Adjusting the obtained FTIR spectra by Gaussian functions, we observed the existence of two possible non-radiative transfer channels with the transition from the D-5(0) to the F-7(2) state of the Eu3+ ions. The first was produced by resonance with the 5th harmonic vibration of OH bonded radicals and the second by resonance with the 14th harmonic vibration of the silicon network. A decrease in OH radicals observed by FTIR was followed by an increase in the lifetime of the D-5(0) state of the Eu3+ ions. However, resonance with higher harmonic orders did not affect the optical properties of the Eu3+ ions. Increases in the lifetime of this transition (similar to 3.3 ms) were obtained from the synthesized sample with the lowest sodium oxide concentration. This lifetime is comparable with the well-known YAG system. Molecular dynamic results show that decreasing sodium oxide content in the host matrix produces structural changes such as decreases in non-bridge oxygen species, which may explain the decreases in OH radical absorption seen in the experimental results. (C) 2013 Optical Society of America