Temperature dependence of the lattice parameters in the 30K superconductor Ba sub (0.6) K sub (0.4) BiO sub 3.

Using powder x-ray diffraction, we have measured the temperature dependence of the lattice parameters of the 30K superconductor, Ba sub (0.6) K sub (0.4) BiO sub 3, in the range 14-300K. We find that within the resolution of our measurement, Ba sub (0.6) K sub (0.4) BiO sub 3 remains cubic over the entire range of temperature with no peak splitting or additional peaks observed. This means that the compound maintains an undistorted, three- dimensional Bi-O array at the superconducting transition temperature. The experiment was performed with a resolution of about 0. 008angstroms sup (-1) and a signal/noise ratio of about 10 sup 3.