Potassium doped barium bismuthates coexisting near the tetra (ortho) and cubic phases boundary: crystal growth and properties
S N Barilo; S V Shiryaev; A G Soldatov; T V Smirnova; V I Gatalskaya; W Reichardt; M Braden; H Szymczak; R Szymczak; M Baran
Журнал:
Superconductor Science and Technology
Дата:
2000-08-01
Аннотация:
We report on the seeded growth of large (up to 2 cm<sup>3</sup>) single crystals of the cubic and orthorhombic phases of Ba<sub>1-x</sub>K<sub>x</sub>BiO<sub>3</sub>. The shape of the crystals varies with potassium content from a cube to a cube-octahedron shape at x~0.2. The flux saturated by Bi<sub>2</sub>O<sub>3</sub> alone with an anode potential of +740 mV were selected to grow cubic Ba<sub>1-x</sub>K<sub>x</sub>BiO<sub>3</sub> crystals with x = 0.67, T<sub>c</sub>~4.5 K. We found that a new cubic phase (x = 0.51, a = 4.266 Å) of crystals could be grown under +970 mV potential and reduced Bi<sub>2</sub>O<sub>3</sub> content in the flux. The crystals grown at ~250 °C acquired a cube-octahedron shape. In turn, crystals of the tetragonal Ba<sub>1.7</sub>K<sub>1.3</sub>Bi<sub>2</sub>O<sub>7</sub> phase (a = 4.25 Å, c = 21.91 Å) up to several mm<sup>3</sup> in size were grown at the same temperature but lower potential and higher Bi<sub>2</sub>O<sub>3</sub> concentration in the flux. Surprisingly the crystals exhibited a weak superconductor-like magnetization.
139.1Кб