Electrosynthesis of KBiO[sub 3]: A potassium ion conductor with the KSbO[sub 3] tunnel structure

Cubic, anhydrous KBiO[sub 3] was synthesized by electrocrystallization from a KOH flux at 175[degrees]C. KBiO[sub 3] crystallizes in space group Im[bar 3] (No. 204) with Z = 12. The room-temperature data were refined to a = 10.0194 [angstrom], V = 1005.8 [angstrom][sup 3] and R = 2.3% for 576 unique reflections. The potassium ion partially occupies three sites in the tunnel structure and the activation energy for ionic conduction is 0.16 eV. The mobility of the potassium ion is low, however, presumably because of its role in stabilizing the Bi-O framework, resulting in an ionic conductivity of 10[sup [minus]5] S/cm at 300[degrees]C. Thermogravimetric analysis shows that KBiO[sub 3] is thermally unstable above 500[degrees]C, decomposing into Bi[sub 2]O[sub 3] and K[sub 2]O. The single-crystal structure, thermogravimetric data, and ionic conductivity of KBiO[sub 3] are described. 34 refs., 3 figs., 4 tabs.