Materials having a zero resistance transition temperature above 200 k and method for maintaining the zero resistance property

A method is described for making a multiphase copper oxide based material Of Y5Ba6Cu11 Oxide containing a phase having a zero resistance transition temperature above about 200K, said method comprising: forming a copper oxide based material precursor consisting essentially of Y, Ba, Cu, and 0, which precursor can be oxygenated to yield said multiphase copper oxide based material; and subjecting said precursor to a high temperature heating process at a temperature greater than 900 C for at least 10 hours; subjecting said precursor to a low temperature oxygenation process in an atmosphere comprising at least about 20% oxygen by volume at a temperature less than about 200 C for at least 72 hours to form said multiphase copper oxide based material