The synthesis of La x Al 2-x O 3 films using ultrasonic spray pyrolysis technique are reported. The films were deposited from a spraying solution of aluminum acetylacetonate (Al(acac) 3 ) and lanthanum(III) nitrate hexahydrate La(NO 3 ) 3 6H 2 O dissolved in N,N-Dimethylformamide on (100) Si substrates. The substrate temperature during was in the range 500-600°C. The mean roughness was lower than 18 Å in all cases. The films were amorphous in all cases. The optical band gap was 5.42 eV and the refractive index was in the 1.64-1.72 range depending of the deposition conditions.

A study of the phase transitions in superconducting thin films of the Thallium-Barium-Calcium-Copper (TBCCO) system is carried out. In particular, it was got the Tl-1223 phase. For this purpose, and using the ultrasonic spray pyrolysis technique, Barium-Calcium-Copper precursor films were first obtained. Upon deposition of the precursor films, and as a second step, they were thallium (Tl) diffused in the one-zone furnace at 860˚C. This methodology resulted in superconducting films that showed a phase transition as follows: Tl-2223 → Tl-2223 + Tl-2212 → Tl-2212 → Tl-1223, achieved between 2 and 7 hours of thallium diffusion. The evidence of the phase transitions was corroborated by the experimental results of X-ray diffraction, energy dispersive spectroscopy and resistance-temperature measurements.