Flux synthesis of cubic potassium antimonate

Although the compound KSbO₃ has been reported to occur in a high temperature cubic polymorph, only the rhombohedral ilmenite phase was obtained in this study for pure material at ambient pressure and temperatures up to about 1350°C in open Pt crucibles or sealed Pt tubes. With the addition of about 2 mole percent SiO₂, B₂O₃ or other oxides of small cations a primitive cubic phase was found with $\text{a}\text{?9.578}\text{A}$. Small single crystals of a body centered cubic phase (a=9.605A) were easily synthesized by a flux evaporation technique at about 1000°C in an open Pt crucible from a composition of about 5 mole % Sb₂O₄:95 mole % KF. The exact composition and structure of this phase (presumably K_1?xSbO_3?xF_x, 0