Influence of alumina addition on crystallization and texturing behavior of LaBGeO 5 glass V.N. Sigaev a , P. Pernice b, * , A. Aronne b , E. Fanelli b , S.V. Lotarev a , E.V. Orlova a , V. Califano c , B. Champagnon c , D. Vouagner c a Mendeleev University of Chemical Technology, Department of Glass, Miusskaya sq., 9, Moscow 125190, Russia b Department of Materials and Production Engineering, University of Naples Federico II, P.le Tecchio, 80125 Naples, Italy c LPCML, UMR 5620 CNRS, Claude Bernard University – Lyon 1, 43 Bd du 11 Novembre 1918, 69622 Villeurbanne, France Received 23 September 2005; received in revised form 4 February 2006 Available online 4 May 2006 Abstract The structure and crystallization behavior of glasses with 25La 2 O 3 Æ 25B 2 O 3 Æ 50GeO 2 composition, melted in platinum (P glass) and corundum (A glass) crucibles, were studied by DTA, X-ray diffraction and FTIR spectroscopy. The Al 2 O 3 dissolved from corundum crucible in the A glass was estimated to be in the range 5–7 wt%. This alumina content had almost no influence on glass transition tem- perature but strongly affected the structure and crystallization behavior of the A glass. In fact, the P glass showed good texture-forming ability: high quality textured glass-ceramic plates based on stillwellite-like LaBGeO 5 crystals were easily obtained. On the contrary, the presence of alumina stabilized the A glass from which binary phases crystallize first, and only afterwards they are transformed in still- wellite by secondary crystallization: so in this glass texturing is hindered. Crystallization and texturing behavior of P and A glasses were well related to FTIR data. P glass contained both threefold and fourfold coordinated boron while in the A glass the presence of alumi- num forced boron to assume almost exclusively threefold co-ordination. Hence the easier crystallization of stillwellite phase and the good textures obtained from the P glass contrary to the A glass, can be well understood since all boron atoms have tetrahedral co-ordination in stillwellite LaBGeO 5 crystal. Ó 2006 Elsevier B.V. All rights reserved. PACS: 81.05.Kf; 71.55.Jv Keywords: Crystallization; Scanning electron microscopy; FTIR measurements 1. Introduction Lanthanum boron germanate (LBG) glasses having composition near the stillwellite-like LaBGeO 5 stoichiome- try exhibit distinct grain-oriented crystallization tendency [1,2]. Well-formed bulk textures based on needle-shaped crystals of ferroelectric LaBGeO 5 were obtained, with an excellent pyroelectric activity [3–5]. Transparent or semi- transparent near-surface thin textured layers of stillwel- lite-like non-linear optical crystals were also obtained from the LBG system [6,7]. Texturing of glasses depends on many factors. One of these is the actual glass composition that can vary with respect to the nominal one because of boron evaporation losses during the melting process. Shimanuki et al. [8] reported that texturing of Pb 5 Ge 3 O 11 ferroelectrics can be compromised by a change of ±0.3% PbO content from the optimal composition. The impurity content, the cooling process, the crystallization thermal conditions are also important [8–11]. All these factors were not investigated enough, so there is still a poor reproducibility of the micro- structure and physical properties of textured glass-ceramics 0022-3093/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2006.02.049 * Corresponding author. Tel.: +39 081 76 82411; fax: +39 081 76 82595. E-mail address: pernice@unina.it (P. Pernice). www.elsevier.com/locate/jnoncrysol Journal of Non-Crystalline Solids 352 (2006) 2123–2128