Detailed analysis of the zero critical temperature improvement in MnYBa2Cu3O7−δ composites from electrical and structural studies

The study was aimed at investigating in a continuous manner the influence of the solid and/or liquid phase sintering on xMn-(1 − x)YBCO (where YBCO represents YBa2Cu3O7−δ) composites, with 0.02 ≤ x ≤ 0.07. The main result is obtained from resistance vs. temperature measurements; in comparison with the pure YBCO, we show that an improvement in the zero resistance temperature is obtained at an optimal sintering temperature, whatever the Mn concentration x of the composite is. From the microstructural study, associated with energy-dispersive X-ray analysis, we detect that, in that case, particular inclusions are formed, with a constant Mn content probably responsible for the zero critical temperature improvement. terpretation is based on the fact that the Mn substitution in the YBCO lattice cannot be fully responsible for this improvement and that the secondary phases play a role in explaining such a phenomenon.