a serial (100 - x)ge25sb10s65-xi (x = 0, 5, 10, 15, 20, 25 and 30 wt%) chalcohalide glasses and ones doped with 0.1 wt% dy3+ rare-earth ions were synthesized and their structural, thermal and optical properties were systematically studied. it indicates that addition of i-2 into ge25sb10s65 glass significantly decreases the connectivity of glass network and average bond energy, and modifies the associated properties. the glass transition temperature and refractive index decrease monotonically, and the density increases almost linearly with the increasing of iodine content in glass. the thermal stability is improved, which has a maximum of delta t-max = 174 degrees c. while the optical bandgap has a peak value at x = 10 wt. the absorption spectra and mid-infrared fluorescence spectra of dy3+ rare-earth ions doped glasses were investigated together with the judd-ofelt analysis. ges2 nano-crystals were found in the sample with x >= 15 wt, which is supposed to induce enhancements of mid-infrared fluorescence at 2.95 and 432 mu m. (c) 2017 elsevier b.v. all rights reserved.