Lazic, BiljanaKruger, HannesKaindl, ReinhardPerfler, LukasKremenović, AleksandarCvetković, VladicaWithers, Raymond2015-12-100897-4756http://hdl.handle.net/1885/63052Large whiskers of a new KAl9O14 polymorph with mullite-type structure were synthesized. The chemical composition of the crystals was confirmed by energy-dispersive X-ray spectroscopy, and the structure was determined using single-crystal X-ray diffraction. Nanosized twin domains and one-dimensional diffuse scattering were observed utilizing transmission electron microscopy. The compound crystallizes in space group P21/n (a = 8.1880(8), b = 7.6760(7), c = 8.7944(9) Å, β = 110.570(8), V = 517.50(9) Å3, Z = 2). Crystals of KAl 9O14 exhibit a mullite-type structure with linear edge-sharing AlO6 octahedral chains connected with groups of two AlO4 tetrahedra and one AlO5 trigonal bipyramid. Additionally, disproportionation of KAl9O14 into K β-alumina and corundum was observed using in situ high-temperature optical microscopy and Raman spectroscopy.Keywords: Chemical compositions; Diffuse scattering; Disproportionations; Edge sharing; Energy dispersive x-ray spectroscopy; High-temperature optical microscopies; mullite-type; Octahedral chains; Single crystal x-ray diffraction; Space Groups; superstructure; Twi diffuse scattering; mullite-type; stacking faults; superstructure; whiskers201310.1021/cm30384762016-02-24