Investigations on the optical properties of Dy3Â + ions doped potassium aluminiumtelluroborate glasses for white light applications

- Under 388 nm excitation, 4F9/2 → 6H13/2 was found to be high intense compared to 4F9/2 → 6H15/2.
- Higher σe of BTKA0.5D glass for 4F9/2 → 6H13/2 transition suggests yellow laser applications.
- I-H model confirms that dipole-dipole interaction is dominant between donor-acceptor ions.
- CIE color coordinates and CCT values suggest these glasses for cool white light applications.

Dy3 + doped potassium aluminiumtelluroborate glasses with the chemical composition 55H3BO3 + (20 − x)TeO2 + 10K2CO3 + 15Al2O3 + xDy2O3 (where x = 0, 0.05, 0.1, 0.25, 0.5, 1.0 and 2.0 in wt%) were prepared following the melt quenching technique and its structural and optical behavior were analyzed through recording FTIR, UV-Vis-NIR, luminescence and decay spectra. The FTIR spectra confirm the presence of different stretching and bending vibrations of BO and TeO network in the prepared glasses. The nephelauxetic ratios (β) and bonding parameter (δ) values were determined from the absorption spectra and these values confirms the increasing covalent nature. The Judd-Ofelt (JO) intensity parameters (Ω2, Ω4, Ω6) have been determined and the Ω2 parameter value is found to increase with the increase in Dy3 + ions concentration thus indicates the increasing asymmetry nature. The luminescence spectra exhibits three distinguishable peaks at around 483 nm, 575 nm and 662 nm corresponding to the 4F9/2 → 6H15/2, 4F9/2 → 6H13/2 and 4F9/2 → 6H11/2 transitions while exciting at 388 nm. The Y/B ratio which signifies the local field environment was found to increase with the increase in the concentration of Dy3 + ions in the present glasses. The luminescence intensity of these transitions is found to quench beyond 0.5 wt% Dy3 + ions concentration which may probably due to the occurrence of possible resonant energy transfer and cross-relaxation mechanisms. The decay measurements were made by monitoring an excitation at 388 nm and emission at 575 nm corresponding to the 4F9/2 → 6H13/2 transition and the decay curve exhibit single exponential behavior at lower concentration and turn to exhibit bi-exponential behavior beyond 0.1 wt% of Dy3 + ion. Employing the Inokuti-Hirayama model, the type of interaction takes place between the donor-acceptor ions has been identified and the parameters like donor-acceptor interaction parameter (CDA), critical distance (R0) were also calculated and discussed. Among the prepared glasses, 0.5 wt% Dy3 + ions doped glass was found to exhibit higher stimulated emission cross-section pertaining to the 4F9/2 → 6H13/2 transition thus suggests its suitability for yellow laser applications. The CIE color chromaticity coordinates (x,y) were determined following the standard Commission International de I'Eclairage (CIE) 1931 chromaticity diagram and the values were found to be in close proximity with the standard white light (0.33, 0.33) for all the prepared glasses thus suggests the suitability of the present glasses for white light generation. Further correlated color temperature (CCT) values were found to agree with the cool white light suggesting the suitability of these glasses for operating in schools, offices etc.