TL-BASED SUPERCONDUCTING FILMS PREPARED BY SPRAY-PYROLYSIS AND VACUUMEVAPORATION

Tl-based films were prepared by the 2-step procedure. First, Ba-Ca-Cu- O precursors were deposited either from an aerosol or by thermal evapo ration on MgO substrates. Thallination of precursors was then performe d at 850 degrees C in flowing oxygen with annealing time up to 30 min. Films were characterized by T-c and X-ray measurements, and their dep th profiles (RBS), surface morphology (SEM) and oxygen Raman modes wer e also investigated. The aerosol deposited films gave T-c = 94-103.5 K . Films grown by thermal evaporation revealed unusual T-c and structur al changes during their 20-months storage in laboratory surroundings. Their T-c has increased from 94 to 106 K.