RARE-EARTH BARIUM NIOBATES - A NEW CLASS OF POTENTIAL SUBSTRATES FOR YBA2CU3O7-DELTA SUPERCONDUCTOR

A class of complex perovskites REBa(2)NbO(6) (where RE=Pr, Nd, Sm and Eu) have been sintered as single phase materials having a high sintere d density and stability, for their use as substrates for YBa2Cu3O7-del ta superconductors. The structure of these materials was studied by X- ray diffraction technique and all of them were found to be isostructur al having a cubic perovskite structure. These newly developed material s do not react with YBa2Cu3O7-delta superconductors even after anneali ng 1:1 volume mixture at 950 degrees C for 15 h. The presence of REBa( 2)NbO(6) upto 20 vol% in the YBa2Cu3O7-delta-REBa(2)NbO(6) composite d id not show any deterimental effect on the superconducting transition temperature of YBa2Cu3O7-delta Dielectric constant and loss factor of REBa(2)NbO(6) were found to be in the range suitable for their use as substrates for microwave applications. Superconducting YBa2Cu3O7-delta thick films screen-printed on these new substrates gave a zero transi tion temperature T(c0)approximate to 92 K and current density approxim ate to 2 x 10(5) A/cm2 at 77 K.