THIN YBCO FILMS PREPARED BY LOW-TEMPERATURE SPRAY PYROLYSIS

Thin YBCO films were prepared from aerosol by a low-temperature deposition process consisting of two steps-the deposition at atmospheric pressure and firing in vacuum degraded by partial pressure of oxygen-both at temperatures not exceeding 600-degrees-C. A stoichiometric 1-2-3 aqueous nitrate solution of Y, Ba and Cu constituents was used as a source of aerosol. MgO and AI2O3 substrates were heated to 140 to 160-degrees-C during deposition. The obtained films were 1 to 10-mu-m thick with T(c) > 80 K and J(c) = 10(3) to 10(4) A cm-2. However, detailed TG, DTG and DTA studies performed by us and others showed that thermal decomposition of the nitrates used only starts at temperatures higher than 200-degrees-C. The use of low substrate temperatures during deposition (140 to 160-degrees-C in our case) is apparently the reason for rather low J(c) values. Optimization of the preparation process is suggested, which could lead to higher J(c) values at processing temperatures not exceeding 600 to 700-degrees-C. Such temperatures are still interesting for substrates with elevated diffusivity into prepared films.