Abstract
Twelve compositions of high Tc superconducting ceramic materials, with the compositios Ba2YCu3O7-δ and Ba2LnCu3O7-δ (Ln=La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu) were synthesized and studied. The authors have focused their studies on the ortho-tetra phase transition in the lanthanide compounds as well as the yttrium compound. The orthorhombic-tetragonal Ba2YCu3O7-δphase boundary in the δ-T daiagram was determind by the detailed isobar thermogravimetric(TG) measurement under the oxygen parial pressures of 1 to 0.01 atm. The transition temperatures of the lanthanide compounds were also measured. It was found that the, transition temperatures depend on the length of the a and b axis in the unit cell. A simple model considering a repulsion energy between oxygen atoms in the c plane was proposed, explaining trends in transition temperature and oxygen content.
Thick film and green sheet powder processing techniques have been studied, with application to electronic components and devices. A paste of calcined powder was made and screen-printed on various substrates. The Tcend was found to be 87K for yttria-stabilized-zirconia substrate. The ceramic body made using green sheet process had the same properties as those of the sample made using conventional powder processing techniques.
