Ca doping of TSMTG-YBa2Cu3O7−δ/Y2BaCuO5 composites
Abstract
Calcium doped YBa2Cu3O7−δ/Y2BaCuO5 bulk samples have been synthesised by the top-seeding-melt-texture growth (TSMTG) process up to 1 wt.% of CaCO3. Calcium additions up to 0.25 wt.% of CaCO3 do not change the decomposition temperature whereas additions of 1 wt.% of CaCO3 lead to an increase of the decomposition temperature of about 10 °C. This difference is not important enough to change the thermal cycle used to process YBa2Cu3O7−δ undoped bulk samples. Microstructure studies show that no precursor or secondary phases containing calcium are present in the samples. Energy dispersive spectroscopy analyses have shown that Ca is present both in the YBa2Cu3O7−δ matrix and the Y2BaCuO5 particles. The position of the calcium atoms in the superconducting matrix is discussed. The calcium doped samples present slightly depressed critical temperatures but drastically depressed critical current densities.