Effect of Al2O3 on structure and properties of Al2O3-K2O-P2O5 glasses

The effect of Al2O3 content on the structure and properties of phosphate glasses Nd3+: Al2O3-K2O-P2O5 was investigated. Deconvolution Raman spectra were used to elucidate the glassy structures and it was observed that with increased Al2O3 content, the vibration frequencies and relative intensities of Q(n) (n represents the number of bridging oxygens (BO) per tetrahedra) changed. The Raman derived glass structure units were used as descriptors to build quantitative structure-property relationship (QSPR) models using the partial least squares (PLS) method to investigate the relationship of the glass structure and different physical properties such as glass transition temperature (Tg), density (rho), and refractive index (n(c)). The glass properties (Tg, rho and n(c)) have positive relationships with the vibration frequency and relative intensity of Q(1Al)(2) (one bridging oxygen bound to Al, and one bridging oxygen bound to K). In contrast, they have negative relationships with the vibration frequency and relative intensity of Q(0Al)(2) (two bridging oxygens bound to K) and Q(3). The increase in Q(1Al)(2) leads to the tightening of the phosphate network and a decrease in the molar volume, resulting in improved glass properties (Tg,. and nc). The Q(1Al)(2) tetrahedra that form phosphate chains or rings is one of the main factors that affect the luminescent properties (sigma(ems), Delta lambda(eff) and tau(trad)) of the Nd3+ ions. With increases in vibration frequency and relative intensity of Q(1Al)(2), the emission cross section (sigma(ems)) decreases, but both the effective line-width (Delta lambda(eff)) and fluorescence lifetime (trad) increase. (c) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement