Spray deposited Tl-Ba-Ca-Cu-O films and bulks subjected to a common anneal

Abstract

Superconducting TI-Ba-Ca-Cu-O (TBCCO) 2212 films have been prepared by annealing the spray deposited precursor Ba-Ca-Cu-O/MgO layers with crude TBCCO pellets. Properties of both films and bulks are described. To deposit the precursor films, an aerosol generated ultrasonically from aqueous nitrate solution was used. The prepared 2212 films were 23 mu m thick; the highest Tc=102 K was obtained in both film and pellet annealed at 850 degrees C for 30 min. The Jc values measured on some films were in the interval 103-104 A cm-2; the XRPD data show rather low grain orientation both in films and in bulks. The X-ray patterns revealed that the film samples contain more than 95 vol.% of 2212 phase; the bulks contain more than 90 vol.% of 2212. The AES depth profiles in the surface layers of films show a slight drop in the Tl content towards the film-substrate interface. From the Raman spectra, XRPD data, structural investigation and physical properties of obtained 2212 phases, correlations among cationic disorder, c axis parameters, Tc values and frequency of the Raman modes were deduced. Results of detailed thermogravimetric TG, DTG and DTA measurements of homogenized precursor Ba-Ca-Cu nitrate and oxide mixtures as well as those of the crude Tl-Ba-Ca-Cu oxide mixture are presented.