Comprehensive study on compositional modification of Tb3+ doped zinc phosphate glass

Series of glass composition (60-x) P₂O₅ -40 ZnO –(x) Tb₂O₃ where x = 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 mol % are prepared by conventional melt quenching technique. X-Ray Diffraction (XRD), FTIR, UV-Vis-NIR and the photoluminescence (PL) spectroscopy are used to characterize the physical, structural and optical behavior of the glass sample. The XRD pattern confirms the amorphous nature and DTA verified the thermal stability of all the glass samples. Glass with 1.5 mol % of Tb₂O₃ possesses the highest thermal stability. Glass density is found to increase proportionally with increasing amount of Tb³⁺ while the molar volume behaves reversely. Six main IR absorption bands centered at about 540, 748, 891, 1085 and 1294 cm^{− 1} are evidenced. The UV-Vis NIR absorption spectra reveals the absorption center band at about 540, 376, 488 and 1920 nm corresponding to the absorption from ⁷F₆ ground state to various excited state of Tb³⁺ ion. The optical band gaps for direct and indirect transition are in the range 4.53–5.07 eV and 4.30 eV-4.56 eV respectively. The Urbach energy decreases with the increasing concentration of Tb₂O₃. The PL emission spectra reveals several prominent peaks at 413, 435, 457, 488, 540, 585 and 620 nm due to electronic transition from ⁵D₃→⁷F₅, ⁵D₃→⁷F₄, ⁵D₃→⁷F₃, ⁵D₄→⁷F₆, ⁵D₄→⁷F₅, ⁵D₄→⁷F₃ and ⁵D₄→⁷F₅ respectively.