Lithium substituted superconducting Y<SUB>1</SUB>Ba<SUB>2</SUB>Cu<SUB>4</SUB>O<SUB>8</SUB> formed in elevated oxygen pressure

Partial substitution of lithium in Y<SUB>1</SUB>Ba<SUB>2</SUB>Cu<SUB>4</SUB>O<SUB>8</SUB> has been accomplished by reacting the constituent oxides with LiOH&#x00B7;H<SUB>2</SUB>O at elevated oxygen pressure (200 bar). T<SUB>c</SUB> falls gradually at a rate of approximately 2 K/at.% of lithium added, up to the solubility limit of ~ 0.13 Li/formula unit. When Li content is increased further T<SUB>c</SUB> remains nearly constant at 57-58 K and the volume fraction of the superconducting phase decreases progressively