High-temperature behavior and structural studies on Ca14Al10Zn6O35

Abstract

Abstract Single-crystals of Ca14Al10Zn6O35 suitable for structural investigations were grown from slow cooling of a melt with the same chemical composition in the range between 1300 and 1000 °C. Diffraction experiments performed at ambient temperature yielded the following crystallographic data: space group F23, a = 14.8468 (6) Å, V = 3272.6 (2) Å3, Z = 4. Structure determination and subsequent least‐squares refinements resulted in a residual of R(|F|) = 1.49% for 753 independent observed reflections and 55 parameters. The chiral structure is based on a tetrahedral framework of corner sharing (Zn,Al)O4-tetrahedra. Zn–Al-distributions among the four crystallographically independent T-sites have been studied. A detailed topological analysis based on natural tiles is presented. Actually, the net can be constructed from a total of four different cages (tiles). The largest cavities (face symbol: [316. 616]) have volumes of about 680 Å3 and host [AlO6][Ca14O36] heteropolyhedral clusters consisting of a central [AlO6] – octahedron surrounded by [CaO6]- and [CaO7]-groups. The calcium cations provide linkage to the tetrahedral framework, in other words, the [AlO6]-unit in the barycenter of the cluster is not directly connected to the framework. Furthermore, thermal expansion has been studied in the interval between 25 and 790 °C using in-situ high‐temperature single‐crystal diffraction. No indications for a structural phase transition were observed. From the evolution of the lattice parameters the thermal expansion tensor has been obtained. The response of the structure to variable temperature has been discussed.