No abstract

' (Brown andLevinson 1987[1978]), and a principle of social solidarity defining degrees of ''empathy'' (Kuno 1987)

A class of complex perovskites REBa2NbO6 (where RE=Pr, Nd, Sm and Eu) have been sintered as single phase materials having a high sintered density and stability, for their use as substrates for YBa2Cu3O7-δ superconductors. The structure of these materials was studied by X-ray diffraction technique and all of them were found to be isostructural having a cubic perovskite structure. These newly developed materials do not react with YBa2Cu3O7-δ superconductors even after annealing 1:1 volume mixture at 950° C for 15 h. The presence of REBa2NbO6 upto 20 vol% in the YBa2Cu3O7-δ–REBa2NbO6 composite did not show any deterimental effect on the superconducting transition temperature of YBa2Cu3O7-δ. Dielectric constant and loss factor of REBa2NbO6 were found to be in the range suitable for their use as substrates for microwave applications. Superconducting YBa2Cu3O7-δ thick films screen-printed on these new substrates gave a zero transition temperature T c0≈92 K and current density≈2×105 A/cm2 at 77 K.