Chiang Mai Journal of Science

  The DyBCO ceramics were fabricated by solid-state reaction method under a normal air atmosphere using a stoichiometric amount (i.e. Dy:Ba:Cu = 1:2:3) of high-purity Dy₂O₃, BaCO₃ and CuO starting powders, which were previously mixed and calcined at 900^oC for 4 h. The green DyBCO pellets were sintered at various sintering temperatures (i.e. 850, 900, 930, 950 and 980^oC) for 2 h. The influence of sintering process on phase formation of ceramics was observed by X-ray diffraction (XRD). The quantitative phase analysis of ceramics was analyzed by fitting the XRD pattern using the PowderCell program. The results showed that the DyBa₂Cu₃O_7-δ composition was identified as the main crystalline phase. At higher temperatures (> 950^oC), the Dy₂BaCuO₅ (Dy-211) secondary phase was observed. The relative fraction of various phases was discussed in relation to phase formation and density change. The SEM-EDS/WDS images of ceramics exhibited irregular shaped grains. The average grain size increased from ~2.3 to ~7.0 µm when the sintering temperature was increased. The possibility of stoichiometric change in DyBCO ceramic due to different processing conditions was also discussed in details.