Exploration of modifier based structural and spectroscopic traits of Eu3+ doped boro-tellurite glasses for solar UV photons converting applications

Abstract

A new series of stable host glass with different modifier cations have been formed with the molar composition15XO + 39B2O3 + 25TeO2 + 10Na2O + 10K2O + 1Eu2O3 (X = Li2, Ca, Sr, Ba, Zn) through traditional glass preparation technique of melt quenching. The effect caused by the incorporation of modifier cations on the radiative assets of Eu3+ ions in the present host glass were inspected through X-ray Diffraction (XRD), Fourier Transformed Infra-Red (FTIR), UV–vis-NIR, photoluminescence and luminescence decay spectral studies at room temperature. The broad diffraction band in the XRD pattern confirms glassy or amorphous nature of the synthesized samples. The functional modes of vibration and structural modules in the prepared glass samples were inspected through FTIR spectra. The 4f − 4f electronic transitions pertaining to the trivalent europium (Eu3+) ions in the new host glasses were scrutinized by UV–vis-NIR absorption studies where in the dominant covalent bonding nature of the Eu3+ ions with its nearby ligands have been confirmed via average nephelauxetic ratio (β) and bonding parameter(δ) values. Optical bandgap (indirect and direct) values were testified to identify the photon energy transparent window and to explore the tendency of the formation of non-bridging oxygens. Luminescence ability of the prepared samples was inspected by exciting at a wavelength of 465 nm. Among the prepared samples, Eu3+ ions emissions were observed and the highest intensity of emission occurred at 612 nm (5D0→7F2) for BTLi:Eu glass. The Judd-Ofelt parameters were estimated and used to evaluate the radiative parameters such as radiative lifetime (τrad), transition probability (A), branching ratio (βR), stimulated emission cross-section (σPE) of all the emissions observed in the produced glasses and the outcomes were equated with the related literature. The colour chromaticity coordinates and colour correlated temperature (CCT) were explored from the emission spectra using CIE 1931 diagram and the CCT values found to lie in the range of 2000–4000 K. The luminescence decay comfortably fitted to the single exponential decay profile which further confirms the non-appearance of energy transfer via mutual interaction amongst Eu3+ ions in all the present glasses. All the observed results indicate the fact that the incorporation of Li+ cations induces more attractive radiative features with 77 % of UV to visible quantum converting efficiency than all other cations used in this contemporary study and among the prepared glasses, BTLi:Eu glass exhibits a better capability in red light emitting electro-optical applications.