title: KSbO(Ge0.32Si0.68)O4, a KTP isomorph.
abstract: A structural model of potassium antimony germanate/silicate (0.32/0.68), KSbO(Ge(0.32)Si(0.68))O(4), has been determined at room temperature. KSbO(Ge(0.32)Si(0.68))O(4) belongs to the KTiOPO(4) (KTP) isomorphic family and is composed of SbO(6) octahedra (site symmetry -1 and 2) arranged in helical chains bridged by (Ge/Si)O(4) tetrahedra. Germanium and silicon have a similar distribution in the crystallographically independent tetrahedra (site symmetry 2). The structure contains large cavities occupied by the K atom. Two partially occupied potassium positions have been identified 1.273 (8) A apart, with an indication of a third potassium position between them. At room temperature, KSbO(Ge(0.32)Si(0.68))O(4) crystallizes in the paraelectric phase of space group Pnan. This phase is found at elevated temperatures for almost all KTiOPO(4) isomorphic compounds and KSbO(Ge(0.32)Si(0.68))O(4) is the second isomorph that is paraelectric at room temperature.
authors.affiliation: Department of Inorganic Chemistry, Chalmers University of Technology, SE-412 96 Göteborg, Sweden. stn@inoc.chalmers.se
authors.forename: S T
authors.initials: ST
authors.lastname: Norberg
authors.forename: G
authors.initials: G
authors.lastname: Svensson
authors.forename: J
authors.initials: J
authors.lastname: Albertsson