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Ba2 Rare Earth Cu3 Superconducting Oxide Films Produced by Pyrolysis From Aqueous Alcohol Nitrate Solutions

IP.com Disclosure Number: IPCOM000101072D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 93K

Publishing Venue

IBM

Related People

Cooper, EI: AUTHOR [+7]

Abstract

Superconducting films of Ba2RECu3O7-x are prepared from aqueous and aqueous-alcoholic mixed solutions of barium, rare earth (RE), and copper nitrates. The solutions are sprayed onto heated (100) orientated MgO, ZrO2 -9%Y2O3 and SrTiO3 substrates to form a dehydrated nitrate precursor which upon subsequent thermal treatment in an oxidizing atmosphere yields the superconducting 2:1:3 compound.

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Ba2 Rare Earth Cu3 Superconducting Oxide Films Produced by Pyrolysis From Aqueous Alcohol Nitrate Solutions

       Superconducting films of Ba2RECu3O7-x are prepared from
aqueous and aqueous-alcoholic mixed solutions of barium, rare earth
(RE), and copper nitrates.  The solutions are sprayed onto heated
(100) orientated MgO, ZrO2 -9%Y2O3 and SrTiO3 substrates to form a
dehydrated nitrate precursor which upon subsequent thermal treatment
in an oxidizing atmosphere yields the superconducting 2:1:3 compound.

      Earlier magnetic film studies with aqueous-alcoholic mixed
solutions of rare-earth iron garnet precursors showed that alcohol
improves the spreading and drying of solutions on substrates.  Here,
however, alcohol significantly lowers the solubility of Ba(NO3)2, and
some compositions tend to phase segregate during film preparation.
Stoichiometric amounts of BaCO3, Y2O3 and CuO according to the
actions in the Ba2YCu3O7-w formula are dissolved in dilute nitric
acid and evaporated to dryness.  Aqueous solutions containing 2wt% of
this nitrate powder are diluted with 30vol.% ethanol to enhance
drying during deposition.  (Ethanol and nitric acid react violently
unless diluted with water and mixed slowly.)  Spraying onto a
substrate held at a high temperature improves the film homogeneity
and should ideally be done over 800oK to achieve instantaneous
decomposition of Ba(NO3)2 and to avoid the formation of BaCO3 .  The
percursors undergo a complex multi-stage decomposition process as
follows:

      The thermal decompositon spectrum for the nitrate mixture shows
three distinct regions.  The first, up to 500oK, is due entirely to
the desorption of water.  The quantity of water released is several
times smaller than that for the nitric oxide and oxygen.  This water
originates almost entirely from the dehydration of Y(NO3)3 .  We base
this assignment on the supporting thermal analyses of the three pure
starting materials, heated in the same fashion as the composite.  The
water is lost in the early stages of heating and is essentially
complete before the onset of the nitrate mixture decomposition.

      The second feature, between 450 and 650oK, is associated with...