In this paper structural, thermal and optical properties of Er3+ doped germanate glasses with the composition of 63.0GeO2-9.8Ga2O3-11.1BaO-4.9X-8.8Na2O-2.5Er2O3 (in mol%), where X = ZnO, TiO2, Al2O3 and Y2O3 are reported. The investigated glasses exhibit low phonon energies (<1000 cm−1) and high glass transition temperature varying between 588 and 642 °C. The Raman spectra evidence about different polymerization degree of the glasses. The thermal treatment leads to the precipitation of various crystals, the composition of which depends on the glass composition. According to the spectroscopic properties Er3+ ions are suspected to have similar local environment in the as-prepared glasses. However, Er-doped crystals are expected to precipitate upon devitrification, which leads to significant change of the spectroscopic properties, in particular increase in the intensity of upconversion and MIR emissions is observed. It is demonstrated that the glasses with Y2O3, ZnO and TiO2 are promising glasses especially for MIR applications.publishedVersionPeer reviewe
