Structural and optical investigations of rare earth doped lead-free germanate glasses modified by MO and MF2 (M = Ca, Sr, Ba)

•Local structure of rare earth doped lead-free germanate glasses was examined.•Optical properties of Eu3 + ions in oxide and oxyfluoride glasses were tested.•Fluorescence intensity ratio R/O for Eu3 + ions in examined systems was calculated.•The luminescence lifetimes of the investigated glasses have been studied.

Rare earth doped lead-free oxide and oxyfluoride germanate glasses were synthesized. The rare earths as an optically active ions were limited to trivalent Eu3 +. One of the glass modifier components is MO (M = Ca, Sr or Ba), which was partially or totally substituted by MF2 in chemical composition. The influence of glass modifiers on structure of lead-free-germanate glasses was examined using X-ray diffraction analysis. In contrast to samples containing modifier MO (M = Ca or Sr), samples with BaO and/or BaF2 are fully amorphous. For the amorphous samples, the emission properties of Eu3 + ions were studied. The emission spectra of Eu3 + ions and their decays in glass samples with different BaF2 contents were analyzed. Several spectroscopic parameters, such as fluorescence intensity ratio R/O (Eu3 +) and measured luminescence lifetime for 5D0 state of Eu3 + are presented and discussed in details.