J Mater Sci Technol ›› 2011, Vol. 27 ›› Issue (2): 189-192.

• Regular Papers • Previous Articles    

Crystallization Behaviour and Nanostructuring in Alkali Niobiosilicate Glasses

E. Fanelli1), P. Pernice1), M. Xiao2,3), A. Aronne1), V.N. Sigaev4)   

  1. 1) Dipartimento di Ingegneria dei Materiali e della Produzione, Universit¶a di Napoli Federico II, Napoli 80125, Italy
    2) Department of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
    3) Key Laboratory of Renewable Energy and Gas Hydrate, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640, China
    4) Mendeleev University of Chemical Technology, Glass and Glass-Ceramics, Miusskaya sq., 9, 125190 Moscow, Russia
  • Received:2009-05-08 Revised:2009-11-25 Online:2011-02-28 Published:2011-02-28
  • Contact: M. Xiao

Abstract: 23K2O·27Nb2O5·50SiO2 (KNS), 13K2O·10Na2O·27Nb2O5·50SiO2 (KNaNS) and 15K212Li2O·27Nb2O5·46SiO2 (KLiNS) transparent glasses were synthesized by melt-quenching technique, and studied by differential thermal analysis (DTA), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) to reveal the effect of the devitrification behaviour on transparent nanostructure. Just above the glass transition temperature Tg in the KNS glass, an unidentified phase was formed, while in KNaNS and KLiNS, mixed-alkali niobate phases with tungsten bronze structure were obtained by bulk crystallization. Heat treatments at Tg performed on the KNS glass resulted in the transparent nanostructure with second order harmonic generation (SHG) activity. Heat treatment for 10 h on KNaNS and KLiNS decreased the first DTA exothermic peaks (at least 24°C), indicating the bulk nucleation, which was confirmed by the DTA in comparison with the powdered as-quenched samples. KNaNS and KLiNS showed similar XRD profiles as the K3Li2Nb5O15 crystal with the five most intense peaks at 22.7, 29.4, 32.3, 46.3 and 52.0 deg. HRTEM micro-graph showed clear-cut nano-sized circular domains and spherical nanocrystals dispersed into the amorphous matrix.