title: Synthesis and structure determination of CaSi(1/3)B(2/3)O(8/3): a new calcium borosilicate.
abstract: This article reports on the identification, synthesis, and in-situ structure determination of a new crystalline calcium borosilicate compound of composition CaSi(1/3)B(2/3)O(8/3). Synthesis was carried out by complete crystallization on annealing from a corresponding glassy composition in the widely studied CaO-SiO2-B2O3 ternary system. The crystallographic structure was determined ab initio using electron diffraction information and the charge flipping algorithm performed on synchrotron and neutron powder diffraction data collected in situ at high temperature. CaSi(1/3)B(2/3)O(8/3) is found to crystallize in the Pna2(1) (no. 33) orthorhombic space group, with a = 12.1025(4) Å, b = 5.2676(1) Å, c = 3.7132(1) Å, and V = 236.71(1) Å(3) at 650 °C. Solid-state (29)Si and (11)B NMR experiments have confirmed the existence of finite chains along the c axis, formed by corner-sharing SiO4 tetrahedra and BO3 units. Silicon and boron species share a crystallographic site, and the Si/B distribution induces different possible arrangements of the chains which are discussed in light of DFT calculations. At room temperature, the existence of a superstructure, resulting from the ordering within nanoscale domains, was explored by transmission electron microscopy.
authors: CNRS, UPR3079 CEMHTI, 1D Avenue de la Recherche Scientifique, 45071 Orléans Cedex 2, France. emmanuel.veron@cnrs-orleans.fr
authors: Emmanuel
authors: E
authors: Véron
authors: Mounesha N
authors: MN
authors: Garaga
authors: Denis
authors: D
authors: Pelloquin
authors: Sylvian
authors: S
authors: Cadars
authors: Matthew
authors: M
authors: Suchomel
authors: Emmanuelle
authors: E
authors: Suard
authors: Dominique
authors: D
authors: Massiot
authors: Valérie
authors: V
authors: Montouillout
authors: Guy
authors: G
authors: Matzen
authors: Mathieu
authors: M
authors: Allix
mesh_terms: D001896:Boron Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry*; D018360:Crystallography, X-Ray; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D017640:Silicates / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D001896:Boron Compounds; D017640:Silicates; D002118:Calcium