High-Pressure Synthesis of Superconducting (Ba_1-xSr_x)₂Cu_1+yO_2+2y+δ(CO₃)_1-y (0.35≤x≤0.6, y≈0.1)

Abstract

A new copper-oxide superconductor containing carbon (Ba 1- x Sr x ) 2 Cu 1+ y O 2+2 y +δ (CO 3 ) 1- y (0.35≤ x ≤0.6, y ≈0.1), which is structurally related to Sr 2 CuO 2 CO 3 , was synthesized under high oxygen pressures of more than 5 atm. The onset temperature for superconduction T c (onset) increased with oxygen partial pressure ( P O 2 ) during synthesis. Optimum P O 2 was about 50 atm and (Ba 0.55 Sr 0.45 ) 2 Cu 1.1 O 2.2+δ (CO 3 ) 0.9 synthesized under 50 atm O 2 showed a T c (onset) of about 40 K and a T c (zero) of about 26 K.