Photoluminescence properties of Er and Er/Yb doped tellurite glass and glass-ceramics containing BiTeO crystals.

Glass and glass-ceramics containing nanocrystals of BiTeO cubic phase co-doped with Er and Yb were prepared by heat treatment of the precursor tellurite glass and investigated for optical applications. Lanthanide doped tellurite glass and glass-ceramics have been extensively investigated because of their optical and photoluminescence performance for technological photonic applications. Er and Er/Yb doped TeO-GeO-KO-BiO tellurite glass compositions were prepared by the conventional melt-quenching method. Photoluminescence results showed the important role played by Yb ions when co-doping with Er ions in comparison with the Er single-doped glass. Due to their larger absorption cross-section, Yb species significantly absorbs 980 nm photons and effectively transfers them to Er ions a set of mechanisms including ground-state absorption (GSA), excited-state absorption (ESA), and energy transfer upconversion (ETU). Er/Yb co-doped sample was chosen for the synthesis of transparent glass-ceramics by controlled heat treatment above for 5 to 120 min. X-ray diffraction patterns, high-resolution transmission electron microscopy (TEM) images, and selected area electron diffraction (SAED) from Er/Yb co-doped glass-ceramic samples were used to verify the nanocrystal precipitation, crystalline phase, and chemical nature. The structural change resulting from the crystallization of BiTeO nanocrystals was evaluated by the Raman shift of the bands between 300-500 cm, which are assigned to the formation of Bi-O-Te linkages and the reduction of [TeO] depolymerized units. The effects of HT time on the glass-ceramic's optical and upconversion photoluminescence properties were studied in the visible range under excitation at 980 nm in terms of the energy transfer mechanisms from Yb to Er. Results indicate that Er/Yb co-doped tellurite glass and glass-ceramics are potential candidates for photonic applications in lighting, energy conversion, and luminescent solar cell concentrators.