SYSTEMATIC X-RAY DIFFRACTION STUDY OF Ba_1-xK_xBiO_3-d SINGLE CRYSTALS. Cheng-Hung Chou, A. Wang, H.K. Fun, T.J. Lee, H.Y. Tang, C.H. Lin, M.K. Wu, Department of Physics, National Tsing Hua University,Hsinchu, Taiwan 30043, R.O.C

Crystal structures of Ba_1-xK_xBiO₃ single crystals (BKBO), grown by the anodic electrocrystallization process, were analyzed to compare with previous studies on sintered powder samples. Results show that BKBO prepared in this way exhibit the same crystal symmetry of space group Pm3m for a wide range of x-values (0.38 to 0.66). This work shows that the content of potassium change with depth. Tc vs. potassium solubility curve has been plotted. In order to assure the uniformity of the composition and to examine the dependence of Tc on oxygen content, thin films of

BKBO on the MgO substrate were prepared by laser ablation technique and their compositions will be checked by grazing incident X-ray diffraction. Thereafter, the resistivity vs. temperature curve were plotted using four probed method. Electron density maps, calculated from room temperature X-ray diffraction data, do not show conspicuous difference between super-conducting and nonsuperconducting samples.