Stability of barium oxides in REBa2Cu3Oy superconductors

We have investigated the stability of BaSnO3, BaZrO3, BaTiO3 and BaNb2O6 in the ErBa2Cu3Oy (Er123) matrix by mixing and sintering powders of Er123 and barium oxides. The degradation of Tc due to the addition of barium oxide was the lowest in the case of BaSnO3 (BSO). BSO-added samples exhibited a Tc above 90 K even for 15 vol% addition and an improved Jc under a magnetic field. XRD and SEM results indicated that BSO was very stable in the Er123 matrix. The dependence of Tc on BSO addition showed similar trends for the sintered samples and Er123 thin films. It was found that the most stable barium oxide in Er123 superconductors was BaSnO3.