PREPARATION OF HIGH-TC SUPERCONDUCTOR THIN-FILMS OF Y-BA-CU-O ON CRYSTALLINE GARNET SUBSTRATES

We report the first successful preparation of thin films of Y-Ba-Cu-O superconductor on single crystal Gadolinium Gallium Garnet (GGG) substrate using pulsed excimer laser ablation method. The as-grown films exhibit superconductivity with an onset at 94K and zero resistance at 91K. The X-ray data shows the films to be highly oriented with a preferred a-axis orientation

Calcium substitution at yttrium site in YBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>y</SUB>

We have successfully synthesized single-phase superconducting Y1-xCaxBa2Cu3Oy for 0&#8804; x&#8804; 0.4 using a coprecipitation technique. All these compounds are orthorhombic with lattice parameters a~3.83 and c varying from 11.69 to 11.67 &#197; . The Tc remains unchanged around 90 K. It may be noted that in these compounds Ca substitutes for Y. On the other hand, it is known that in the compounds where Ca substitutes for Ba, the structure changes to tetragonal and Tc decreases rapidly. [See G. J. Baldha, R. B. Jotania, H. H. Joshi, H. N. Pandya, and R. G. Kulkarni, Solid State Commun. 71, 839 (1989)]. Furthermore, these compositions sinter much better than pure 1:2:3 and one gets high-density pellets (&#x22D9; 95% of total density) at relatively lower temperature (&#171; 950 &#176; C)