On the existence of a discrete series of KnBamBim+nOy superconducting phases

The solubility of Bi2O3 in a KOH melt at 200, 250, and 300 degreesC was det ermined for the first time. Superconducting KBaBiO crystals were grown upon electrolysis of a KOH melt saturated with Bi2O3 at different barium concen trations. The cationic composition of crystals was determined by elemental analysis in a transmitting electron microscope. The phases of the KnBam+nOy series derived from the BamBim+nOy series (m = 1, 2,...; n = 0, 1, 2,..,) were identified. The phases of composition (K : Ba : Bi) 1 : 2 : 3, 3 : 5 : 8, 2 : 3 : 5, 3 : 4 : 7, 5 : 6 : 11, 1 : 1 : 2, 5 : 4 : 9, and 3 : 2 : 5 h ave the temperatures (T-c) of the superconducting transition onset of 35, 3 2, 30, 17, 20, 25, 8, and 11 K, respectively. The mean oxidation state of b ismuth in these phases is 4.35-4.56. The electron diffraction images of the superconducting phases of composition 1 : 2 : 3, 3 : 5 : 8, 2 : 3 : 5, 3 : 4 : 7, 5 : 6 : 11, and 1 : 1 : 2 show superlattice reflections with the ve ctor q = 1/2[001] along one axis, which points to a non-cubic symmetry of t he KnBamBim+nOy structures.