Photoluminescence properties of Er 3+ and Er 3+ /Yb 3+ doped tellurite glass and glass-ceramics containing Bi 2 Te 4 O 11 crystals.

Glass and glass-ceramics containing nanocrystals of Bi 2 Te 4 O 11 cubic phase co-doped with Er 3+ and Yb 3+ 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 3+ and Er 3+ /Yb 3+ doped TeO 2 -GeO 2 -K 2 O-Bi 2 O 3 tellurite glass compositions were prepared by the conventional melt-quenching method. Photoluminescence results showed the important role played by Yb 3+ ions when co-doping with Er 3+ ions in comparison with the Er 3+ single-doped glass. Due to their larger absorption cross-section, Yb 3+ species significantly absorbs 980 nm photons and effectively transfers them to Er 3+ ions via a set of mechanisms including ground-state absorption (GSA), excited-state absorption (ESA), and energy transfer upconversion (ETU). Er 3+ /Yb 3+ co-doped sample was chosen for the synthesis of transparent glass-ceramics by controlled heat treatment above T g for 5 to 120 min. X-ray diffraction patterns, high-resolution transmission electron microscopy (TEM) images, and selected area electron diffraction (SAED) from Er 3+ /Yb 3+ 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 Bi 2 Te 4 O 11 nanocrystals was evaluated by the Raman shift of the bands between 300-500 cm -1 , which are assigned to the formation of Bi-O-Te linkages and the reduction of [TeO 3 ] 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 3+ to Er 3+ . Results indicate that Er 3+ /Yb 3+ co-doped tellurite glass and glass-ceramics are potential candidates for photonic applications in lighting, energy conversion, and luminescent solar cell concentrators.