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(3)) single crystals of the cubic and orthorhombic phases of Ba1-xKxBiO3. The shape of the crystals varies with potassium content from a cube to a cube-octahedron shape at x similar to 0.2. The flux saturated by Bi2O3 alone with an anode potential o f +740 mV were selected to grow cubic Ba1-x,KxBiO3 crystals with x = 0.67, T-c similar to 4.5 K. We found that a new cubic phase (x = 0.51, a = 4.266 Angstrom) of crystals could be grown under +970 mV potential and reduced Bi 2O3 content in the Bur. The crystals grown at similar to 250 degrees C acqu ired a cube-octahedron shape. In turn, crystals of the tetragonal Ba1.7K1.3 Bi2O7 phase (a = 4.25 Angstrom, c = 21.91 Angstrom) up to several mm(3) in size were grown at the same temperature but lower potential and higher Bi2O 3 concentration in the flux. Surprisingly the crystals exhibited a weak sup erconductor-like magnetization.