Effect of cerium substitution on the superconducting state of Ba_0.6K_0.4BiO₃

The superconducting compound Ba_0.6K_0.4BiO₃ has one of the highest critical temperatures (T_c = 30 K) of any non-cuprate oxide. In this study, we probed its superconducting properties by studying the impact of chemical substitution with Ce on the system Ba_0.6-xCe_xK_0.4BiO₃. The objective of this study was to measure the effect of introducing magnetic moments by comparing the x-dependence of T_c in Ba_0.6-xCe_xK_0.4BiO₃ with the previously established behavior of Ba_0.6-xLa_xK_0.4BiO₃. Our polycrystalline samples, synthesized using the molten salt technique, exhibited suppressed T_c values compared with that of Ba_0.6K_0.4BiO₃; however, we were unable to observe a clear correlation between measured lattice parameter values and x, suggesting that the molten salt synthesis method we used is unable to finely control the Ce content of the samples. Additional measurements will be required to determine the exact stoichiometry of the samples and x-ray photoemission spectroscopy will be required to determine the oxidation state of Ce ions. In this poster, x-ray diffraction and magnetic susceptibility measurements will be presented and compared with results from Ba_0.6-xLa_xK_0.4BiO₃.