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2006-12-01 - Colloque/Présentation - communication orale - Anglais - 1 page(s)

Maury Nathalie , Cambier Francis, Erauw J.-P., Simons J., Gonon Maurice , "Glass-Ceramics in the Sr-Ti-Si-O system : Effect of K2O addition on the crystallisation of Fresnoite Sr2TiSi2O8" in BCerS 06, Mol, Anvers, Belgique, 2006

  • Codes CREF : Matériaux céramiques et poudres (DI2744)
  • Unités de recherche UMONS : Science des Matériaux (F502)
  • Instituts UMONS : Institut de Recherche en Science et Ingénierie des Matériaux (Matériaux)

Abstract(s) :

(Anglais) Sr2TiSi2O8 is piezoelectric, pyroelectric, but non ferroelectric. To maximise their polar properties, crystals must be (00l) oriented. Unlike ferroelectric materials (single crystals and ceramics), the electrical domain configuration of the non ferroelectric crystalline phases in the glass ceramics cannot be switched by an externally applied electric field. Thus both the crystallographic and polar orientation must be achieved during the crystallisation of glasses. The major advantage of the non-ferroelectricity is that the materials are free from any aging or depoling effects. The present work investigates recrystallisation of different glasses compositions in order to obtain bulk crystallisation of single Sr2TiSi2O8 with favourable crystal texture. Glasses were prepared from compositions based on SrO TiO2 SiO2 B2O3 and K2O. These glasses were then annealed to obtain an optimal recrystallisation. A glass ceramic containing 98-99% of highly (00l) oriented Sr2TiSi2O8 and 1-2% SrTiO3 as crystalline phases was obtained. From a thermodynamic point of view, crystallisation respects the principle of minimisation of surfaces and interfaces energies. Moreover, interface energy between growing crystals and glass is function of the viscosity. So, the influence of the viscosity of the parent glasses on crystallisation and orientation of the crystallites was studied. Different compositions with varying amount of K2O were studied. Dilatometric measurements on glasses showed that the glass transition temperature increases with the increase of concentration of K2O. Glasses were then heated at 900°C during 1h and orientation was studied by XRD. Orientation coefficient increases with the increase of concentration of K2O. We conclude that K2O, by mean of the viscosity, plays an important role on the orientation. Next stage of this work will be to measure surfaces and interfaces energies and to modelise crystallisation.