Beschreibung:
<jats:title>Abstract</jats:title><jats:p>RbSbO<jats:sub>3</jats:sub> crystallizes in different polytypes composed of trigonal [SbO<jats:sub>3</jats:sub>]<jats:sup>−</jats:sup> and [Rb]<jats:sup>+</jats:sup> layers, which can appear in two orientations with respect to <jats:italic>m</jats:italic><jats:sub><100></jats:sub> and <jats:italic>m</jats:italic><jats:sub><120></jats: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: MDO<jats:sub>1</jats:sub> (, <jats:italic>c</jats:italic> ≈ 19.8 Å, isotypic to ilmenite‐like KSbO<jats:sub>3</jats:sub>) and MDO<jats:sub>2</jats:sub> (, <jats:italic>c</jats:italic> ≈ 39.2 Å, isotypic to AgRuO<jats:sub>3</jats:sub>). Crystals grown from RbF:Sb<jats:sub>2</jats:sub>O<jats:sub>5</jats:sub> in a 2:1 ratio are MDO<jats:sub>1</jats:sub>:MDO<jats:sub>2</jats:sub> allotwins, whereas crystals grown from a 12:1 mixture are composed of MDO<jats:sub>2</jats:sub> only. The stacking ambiguity leads to twinning by rotation about <100> or <120>. KSbO<jats:sub>3</jats:sub> crystals grown from KF:Sb<jats:sub>2</jats:sub>O<jats:sub>5</jats:sub> are composed of the MDO<jats:sub>1</jats:sub> polytype only. The crystals are fourfold twins owing to stacking faults. A detailed description of the analysis of the diffraction data is given.</jats:p>