The 1.8 mu m emission properties of Tm3+-doped zinc tellurite glasses modified by the substitution of ZnF2 are investigated in this paper. The thermal stability, Raman and phonon sideband spectra, transmission and absorption spectra, emission spectra and decay curves are discussed. It is found that substitution of fluoride ions into the zinc tellurite matrix produces dramatic increase in the emission lifetime of Tm3+ 1.8 mu m emission. Absorption, Raman and phonon sideband spectra are used to estimate the local structure of Tm3+ ions. These analyses indicate structural change around Tm3+ ions caused by substitution of fluoride ions monitors the increased intrinsic radiative lifetimes. An increase in the measured radiative lifetimes of the Tm3+:F-3(4) -> H-3(6) transition is observed. The origin has been discussed and the reduction of OH- absorption, decrease of maximum phonon energy and phonon density are considered to be dominant in all of the nonradiative relaxations. (C) 2014 Elsevier Ltd. All rights reserved.