Rotter, M., & Stöger, B. (2020). RbSbO₃: A Simple Structure with Complex Polytypism. Crystal Research and Technology, 55(5), 1900164. https://doi.org/10.1002/crat.201900164
Condensed Matter Physics; General Materials Science; General Chemistry; polytypism; allotwinning; order-disorder theory; partial symmetry
-
Abstract:
RbSbO3 crystallizes in different polytypes composed of trigonal [SbO3]− and [Rb]+ layers, which can appear in two orientations with respect to m<sub><100></sub> and m<sub><120></sub>, respectively. The order-disorder (OD) polytype family comprises four polytypes of a maximum degree of order (MDO), of which two are realized in actual crystals: MDO1 (R-3, c ≈ 19.8 Å, isotypic to ilmenite-like KSbO3) and MDO2 (R-3c, c ≈ 39.2 Å, isotypic to AgRuO3 ). Crystals grown from RbF:Sb2O5 in a 2:1 ratio are MDO1:MDO2 allotwins, whereas crystals grown from a 12:1 mixture are composed of MDO2 only. The stacking ambiguity leads to twinning by rotation about <100> or <120>. KSbO3 crystals grown from KF:Sb2O5 are composed of the MDO1 polytype only. The crystals are fourfold twins owing to stacking faults. A detailed description of the analysis of the diffraction data is given.
