Chiang Mai Journal of Science

Dysprosium barium copper oxide (DyBCO) ceramic was successfully prepared by a solid-state reaction and sintering method. The DyBa2Cu3O7-d powder was synthesized by calcining its stoichiometric binary-oxides mixture at 900°C for 4 h. The DyBCO powder was compacted into  pellets and sintered at 930°C for 2 h under normal air atmosphere. Phase identification was determined using an X-ray diffractometer (XRD). The quantitative phase analysis of ceramics was analyzed by fitting the XRD pattern using the GSAS-II program. The surface morphology was observed by scanning electron microscopy (SEM) with chemical composition identification from WDS mode. The result of XRD showed that the DyBa2Cu3O7-d (Dy-123) was identified as the main crystalline phase. The surface of Dy-123 ceramic exhibited a typical elongated form with an average grain size of ~ 3.74 mm. The compositional ratio of polished DyBCO ceramic was approximated to be Dy: Ba: Cu = 1: 2.13: 2.94. The total thermal conductivity values (k) of the DyBCO ceramic were found to decrease with increasing temperature. The k value was about 2.67 W/m-K at 298 K and 0.88 W/m-K at 973 K. The electrical conductivity (s) of DyBCO sample showed semiconducting to metallic-like transition after the temperature increased more than 700 K. The Seebeck coefficient (S) behavior may be attributed to low hole mobility of O-Cu-O chain and the inherent tetragonal structure at high temperature region. The maximum ZT value was about 1.38´10-2 at highest temperature measured.