| 摘要 |
The invention comprises metal oxide materials which exhibit bulk superconductivity at a Tc in excess of 85K in some cases, within the formula R1-xBa2-yAx+yCuaO8- delta where: O</=x<0.3 and 0</=y<0.3 provided that x+y NOTEQUAL 0, -0.25 < delta < 0.25 3.9 < a < 4.1 R is Y, La, Nd, Sm, Eu, Gd, Ho, Er, Tm or Yb or any combination thereof, Ba is Ba or Ba partially substituted by either or both of Sr and La, A is most preferably Ca but may be Li, Na, K, Rb or Cs, or any combination thereof, Cu is Cu or Cu partially substituted by Ag, Au, Hg, Tl, Bi, Pb, Sb or Ga, or any Periodic Table transition metal element or Group 3A, 4A or 5A metal or any combination thereof, and O is O or O partially substituted by N, P, S, Se, or F or any combination thereof. Novel processes for preparation of the materials comprising reacting precursor materials for between 1 and 300 hours at a temperature T and oxygen partial pressure Po2 satisfying the equation T < 1220 - 180L + 21L<2> where L = log10Po2 are also disclosed and claimed. The preparation reaction may be carried out as a solid state or liquid flux reaction of precursor materials in stoichiometric proportions and an alkali metal flux, catalyst or reaction rate enhancer comprising an oxide, chloride, nitrate, hydroxide or carbonate of the alkali may be employed. |
