124 SUPERCONDUCTOR STABILIZED BY HOLE DONOR (CA) ALONG WITH ACCEPTOR (LA) SUBSTITUTION

Substitution of Ca2+ in place of Y3+ together with equal substitution of La3+ for Ba2+ in Y-Ba-Cu-O system at elevated P(O2) extends the stability range of 124 up to a total (Ca+La) concentration of 0.6 atoms per formula unit. The extended stability range of the 124 structure with donor and acceptor co-doping indicates that the relative stability of 124 versus 123 phase is determined to some extent by the hole concentration. The Tc of 124 remains nearly unaffected by even large substitutions of Ca and La so long as they are balanced, so as to give the correct hole concentration; the variation of Tc with separate donor or acceptor doping is caused primarily by the change of hole concentration and Ba does not appear to play a unique role in the high temperature superconductors of the 123 124 family. © 1990.