Optical and spectroscopic behavior of Eu3+ doped heavy metal phosphate glasses

Abstract

Europium (Eu3+)-doped heavy metal phosphate glass systems have been synthesized by melt-quench technique. Optical as well as spectroscopic characteristics are analyzed in detail. X-ray diffraction (XRD) pattern of synthesized samples confirms their glassy nature. Optical band-gap (Eg) for the synthesized samples has been calculated using different methods. Refractive index and other parameters such as dielectric constant, molar refraction, reflection losses, and polarizability have also been determined for prepared glass samples. Photoluminescence properties are examined from the excitation as well as emission spectra and results revealed prominent emissions in red region. The optical band gap for the prepared samples has been evaluated using three different methods viz. Tauc's method, absorption spectrum fitting (ASF) method and differential absorption spectrum fitting (DASF) method. Similar results have been obtained by all the three methods. Judd-Ofelt (J-O) theory has been employed to emission bands of Eu3+ ions for determination of phenomenological intensity parameters i.e. omega(2), omega(4) and omega(6), radiative rate, branching ratio and radiative lifetime. J-O analysis revealed that the large value of omega(2) parameter indicated high covalency between metal-ligand bonds along with the distortion among symmetric sites of Eu3+. Branching ratio (beta(R)) is greater than 0.5 for D-5(0)-> F-7(2) (transition) indicating their prospective for usefulness in laser-based applications. High branching ratio values and color purity suggests the potential use of glass samples for red laser applications.