Spray pyrolysis for highT_csuperconductors films

Abstract

Spray pyrolysis at high temperature is reviewed and applied to the formation of epitaxial thick layers of YBa 2 Cu 3 O 7 (YBCO). The necessary conditions to enhance the texture quality and the critical current density are discussed. High critical current densities, over 1.0 MA cm −2 (at 77 K, self-field), are reported, making this technique very promising for low cost applications. This emphasizes the need for more comprehensive studies regarding the chemical phenomena involved in film deposition by spray pyrolysis at high temperature, especially those concerning local equilibrium and reactions occurring in the area involved in the deposition.

Development of YBa2Cu3O7−xsuperconducting films on (100) SrTiO3and (110) Ag substrates by chemical spray pyrolysis

“…As reported by Odier et al, 17 M. Langlet et al, 23 spray pyrolysis deposition is generally divided into three principal modes depending upon the temperature range of the pyrolysis: (1) at a low temperature, the spray droplets reach the substrate as a solution and liquid films possibly form. If the solvent evaporates from the droplets and if hydrolysis takes place, then gel films can grow in the so-called 'pyrosol-gel' process; (2) if the particles receive a sufficiently large amount of heat during their routes, the solvent evaporates and dry particles precipitate.…”

“…Thus, the high temperature spray pyrolysis technique could be classified among the numerous chemical vapour deposition methods. However, an alternative 17 would be that CuO is deposited on a hot substrate from a nitrate solution and a powdered film is obtained, due to a decomposition of the nitrate into CuO small particles in the mist. The film is formed by small solid particles that aggregate to form a film.…”

“…The solution "g" with a proportion of Y : Ba : Cu = 1 : 3.2 : 0.6 gives the best Y-123 layer, with a composition of almost exactly Y : Ba : Cu = 1 : 2 : 3, which was not very well comparable with some reported results. 17,19 We consider that the difference is mainly due to the differences of deposition parameters and reactor characteristics. It is found that the optimization of the composition of the solution also depends on other parameters, such as the deposition temperature and the gas flow.…”

“…It is a fast, low cost and nonvacuum technique that is used for deposition of precursors for the phase formation of many materials, including oxides, ceramics and glasses [5][6][7][8][9][10][11][12][13][14] at a high temperature and deposition rate. This technique currently offers a very promising alternative for the development of coated conductors and has been investigated by the Grenoble group (Vergnières et al 15,16 and Odier et al 17 ) and by Kim et al, 18 as an alternative to vacuum based technologies for the deposition of YBCO on biaxially textured substrates. Kawai et al 19 reported the first deposition of Y-123 on SrTiO 3 and YSZ substrates by spray pyrolysis soon after the discovery of YBCO.…”

Preparation of high Jc YBCO films on LAO by spray pyrolysis process using nitrate precursors

“…Precursor mists are decomposed thermally as chemical vapor and deposited as films on the substrate surface. Several groups have studied on this spray pyrolysis method for the fabrication of YBCO films at atmospheric pressure [6][7][8][9]. Vergniéres et al [9] reported that good quality YBCO films were deposited on metallic substrate as well as on single crystal substrate but the J c of the films still much lower than 1 MA/cm 2 .…”