A novel microstructure is formed on the single crystal surfaces of the oxide superconductorBa0.6K0.4BiO3(BKBO). Micron-sized barium islands periodically grew on the mother crystal during electrocrystallization of BKBO. Experimental analysis suggested the relation of this unusual microstructure to the Liesegang rings well-known for a crystal growth in gels. The present discovery provides a potential technology for fabricating microstructures on substrates of solids. ©1998 American Institute of Physics.