Potassium doped barium bismuthates coexisting near the tetra (ortho) and cubic phases boundary: crystal growth and properties

We report on the seeded growth of large (up to 2 cm super(3)) single crystals of the cubic and orthorhombic phases of Ba sub(1-x)K sub(x)BiO sub(3). The shape of the crystals varies with potassium content from a cube to a cube-octahedron shape at x to approximately 0.2. The flux saturated by Bi sub(2)O sub(3) alone with an anode potential of +740 mV were selected to grow cubic Ba sub(1-x)K sub(x)BiO sub(3) crystals with x identical with 0.67, T sub(c) to approximately 4.5 K. We found that a new cubic phase (x identical with 0.51, a identical with 4.266 angstroms) of crystals could be grown under +970 mV potential and reduced Bi sub(2)O sub(3) content in the flux. The crystals grown at approximately 250 degree C acquired a cube-octahedron shape. In turn, crystals of the tetragonal Ba sub(1.7)K sub(1.3)Bi sub(2)O sub(7) phase (a identical with 4.25 angstroms, c identical with 21.91 angstroms) up to several mm super(3) in size were grown at the same temperature but lower potential and higher Bi sub(2)O sub(3) concentration in the flux. Surprisingly the crystals exhibited a weak superconductor-like magnetization.