Experimental and theoretical studies of Dy3+ doped alkaline earth aluminosilicate glasses

Several investigations on rare earth (Sm3+, Eu3+, Tb3+) doped aluminosilicate glasses in the last few years showed strong changes in the luminescence properties in dependence on the type and concentration of the network modifier ions. In this article Dy3+-doped alkaline earth aluminosilicate glasses of the molar composition 35 MO·10 Al2O3·55 SiO2 (M=Ba, Sr, Ca and Mg) were prepared by using the melt quenching technique. Differential scanning calorimetry (DSC) measurements of these glasses were carried out. Direct and indirect optical band gaps were calculated based on the glasses UV absorption spectra. The Judd-Ofelt (J-O) theory was used to evaluate the three intensity parameters from the experimental oscillator strengths. Using the J-O intensity parameters, several radiative properties such as spontaneous transition probabilities (AR), radiative branching ratios (βR) and radiative lifetimes (τR) were determined. The photoluminescence spectra obtained by the excitation wavelength of 349 nm show three emission bands at 482 (blue), 574 (yellow) and 660 nm (red) corresponding to the 4F9/2→6H(15/2, 13/2, 11/2) transitions, respectively. From the visible emission spectra yellow to blue (Y/B) intensity ratios and chromaticity coordinates were calculated. In the investigated glasses the Y/B ratio is systematically increased with increasing size of the network modifier ions. The lifetimes of the 4F9/2 metastable state were also measured. All properties are discussed in relation to the effect of the different network modifier ions on the structure of the glasses and compared to literature data.