Preparation and properties of electrochemically grown Ba_1-xK_xBiO_y single crystals with wide potassium composition range

Abstract

The single crystals of Ba_1-xK_xBiO_y (BKBO) with wide potassium composition range (x=0-0.6) were synthesized by electrochemical method. As grown crystal shows high superconducting transition temperature (-30K) and narrow transition width without oxygen annealing. The quantitative chemical analyses were performed for those crystals by EPMA, TGA and iodometry. Though oxygen content of as grown crystals decreases with potassium content increases, Oxygen deficiency is as low as 0.05. The crystals grown electrochemically is considered to be in high oxidation state. It is revealed that both potassium and oxygen play a key role in the superconductivity of BKBO.