Thin YBCO films prepared by low-temperature spray pyrolysis

Abstract

Thin YECO 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 "C. A stoichiometric 1-24 aqueous nitrate solution of Y. Ba and Cu constituents was used as a source of aerosol. MgO and AI,O, substrates were heated to 140 to 160°C during deposition. The obtained films were 1 to 10pm thick with T, > 80 K and J, = lo3 to 10' Acm-'. However, detailed TG, OTG and OTA studies performed by us and others showed that thermal decomposition of t h e nitrates used only starts at temperatures higher than 200°C. The use of low substrate temperatures during deposition (140 to 160 "C in our case) is apparently t h e reason for rather low J. values.J. values at processing temperatures not exceeding 600 to 700°C. Such temperatures are still interesting for substrates with elevated diffusivity into prepared films.

Spray pyrolysis for highTcsuperconductors films

“…above the decomposition temperature of the copper nitrate. We then confirm similar trends that were reported previously [16][17][18][19]21] for YBCO deposition. Such an effect has also been observed for a The temperatures are given by a thermocouple located at the back face of the deposition device.…”

“…They emphasize the role of convection in the transport toward the surface where the deposition 'resembles' that of CVD. Later, Jergel et al [17,18] confirmed that high temperature would probably give better results in terms of J c , mostly because a higher surface diffusion enhances sintering and decreases the roughness.…”

In-plane aligned YBCO thick films grownin situby high temperature ultrasonic spray pyrolysis

“…A secondary heat treatment is required to form YBCO and the films generally have rough surfaces with pinholes and cracking. Maximum J c under these conditions are in the range of 10 3 -10 4 A cm −2 [11]. High-temperature spray pyrolysis occurs at temperatures above 500 • C. These films require a copper deficient precursor solution and are smoother and denser [12].…”

Spray pyrolysis of epitaxial YBCO films on (100) single crystal SrTiO3substrates

“…The appearance of the curve is complex because decomposition can take place by more than one step. Further information on nitrate decomposition is given by Jergel et al [13]. The important point to note is that complete decomposition of the present solution, consisting of a mixture of the component nitrates has taken place by 750 • C.…”