New superconducting compound in the K-Bi-O system was obtained under high pressure. Pure perovskite phase can be prepared for K1-XBi1+XO3 in the range x = 0.0-0.2. Bulk superconductivity with Tc of 10.2 K is observed for samples K1-x Bi1+xO3 with x = 0.0-0.1. Transition temperature Tc does not change within this interval, though deviation from the range x = 0.0-0.1 leads to deterioration of superconducting properties. X-ray diffraction showed that the structure of the superconducting samples is cubic perovskite, which was confirmed by electron diffraction study. After comparing the present results with known bismuth oxide based superconductors we conclude that doping level plays a predominant role in determining the magnitude of Tc in these materials.
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