Effect of ZnO on the spectroscopic properties of Dy3+ doped zinc telluroborate glasses for white light generation

Influence of ZnO concentration (0 to 35 wt%) on the spectroscopic properties of the Dy3+ doped zinc telluroborate glasses prepared by melt quenching technique has been studied and reported. Their structural and optical properties have been examined through Fourier transform infrared spectroscopy, optical absorption, photoluminescence and lifetime measurements. Nature of metal-ligand bond in the glass matrix was examined through Nephelauxetic ratio (β) and bonding parameter (δ) values. The bonding parameter, δ increases from −0.976 to −1.115 with increasing concentration of ZnO, indicating predominant ionic character of the Dy3+-ligand bond. Judd-Ofelt parameters (Ω2, Ω4 and Ω6) were obtained from the absorption measurements. Addition of ZnO leads to an increase in the Ω2 value indicating a larger asymmetry around the Dy3+ ion site. The decay profile of 4F9/2 state of Dy3+ ions exhibits bi-exponential nature. Application of Inokuti-Hirayama model indicates the quenching to be caused by dipole-dipole relaxation. Stimulated emission cross section, chromaticity colour coordinates (0.37, 0.41), colour correlated temperature value (4371 K) and colour purity (35%) were found to be good for TB30ZD glass. Hence it is suggested to be a suitable candidate for laser and white light emitting diode applications.