Calcium doping into YBa2Cu3Oy ceramics by the SOED method

Calcium doping into YBa2Cu3Oy (YBCO) ceramics by the SOED (solid oxide electrochemical doping) method was examined in detail. The electrolysis system consists of(+)Ag/Ca-beta "-Al2O3/YBCO/Ag-beta " Al2O3/Ag(-) where the Ba2+ ion in YBCO is substituted by a Ca2+ ion under electrical force (electro-substitution). Ca2+ is mainly doped into the grain boundaries at low current density but is doped into the grain bulk as well as the grain boundaries at high current density. The amount of the doped Ca2+ ion saturated with an increase in electrolysis time, because the Ca2+ ion moves through the YBCO sample into the Ag-beta "-Al2O3 during the electrolysis. The unit cell volume of the YBCO whose grain bulk was doped with Ca2+ was much smaller than that doped by the conventional doping method, based on the Ba vacancy produced by the present electro-substitution. The Ca doping mechanism in this system is discussed in detail.