Some unknown peaks are observed in TiO2-added samples. Similar unknown peaks were determined by WDX analysis as Ba2TiO4 [17]. It was attributed that the titanate particles absorbing barium from the matrix and BaTiO3 react
with the Ba-rich melt to form Ba2TiO4 during the melt processing. According to the XRD peaks, we can speculate that the solubility of TiO2 in Y123 structure is very small and small concentration of Ti may actually occupy the barium sites and does not enter yttrium sites during the formation of the Y123 super- conducting phase.