Consecutive inert and oxygen atmosphere sintering in the synthesis of LaBa2Cu3Oy with T(R = 0)>90 K

Abstract

Combinations of inert atmosphere sintering and oxygen atmosphere sintering have previously been reported as necessary for the synthesis of LaBa2Cu3Oy superconductors which achieve zero resistance at temperatures above 90 K. Sintering under oxygen atmosphere only is known to produce La(1+x)Ba(2−x)Cu3Oy, in which La is substituted for Ba in the crystal lattice. The latter substituted compounds achieve zero resistance at temperatures well below the boiling point of liquid nitrogen. In this work, we show that during the initial inert atmosphere sintering step, LaBa2Cu3Oy powder decomposes, in part, into several intermediate compounds. These compounds are then recombined in the subsequent oxygen atmosphere sintering step to form LaBa2Cu3Oy, which achieves zero resistance at temperatures above 90 K. We propose that the net effect of these two processing steps is to inhibit the substitution of La for Ba in the lattice of the fully processed material.