Electrical and Thermal Transport Properties of Dysprosium Barium Copper Oxide Ceramic

Dysprosium barium copper oxide (DyBCO) ceramic was successfully prepared by a solid-state reaction and sintering method. The DyBa2Cu3O7-delta powder was synthesized by calcining its stoichiometric binary-oxides mixture at 900 degrees C for 4 h. The DyBCO powder was compacted into pellets and sintered at 930 degrees 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 similar to 3.74 mu m. The compositional ratio of polished DyBCO ceramic was approximated to be Dy: Ba: Cu = 1: 2.13: 2.94. The total thermal conductivity values (kappa) of the DyBCO ceramic were found to decrease with increasing temperature. The. value was about 2.67 W/m-K at 298 K and 0.88 W/m-K at 973 K. The electrical conductivity (sigma) 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 1.38x10(-2) at highest temperature measured.