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Coated conductor synthesis through aqueous sol-gel chemistry

Veerle Cloet (UGent) , Jonas Feys (UGent) , Serge Hoste (UGent) and Isabel Van Driessche (UGent)
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Abstract
High temperature superconductors such as YBa2Cu3O7 (Tc=92 K) can't be produced in long lengths because of their brittle ceramic nature. Another problem in using bulk YBCO is the absence of texture, biaxial texture is necessary to assure the quality of the superconductor. A solution to both problems is presented by the coated conductor structure. This structure consists of a flexible metallic tape (Ni-5at%W) coated with multiple buffer layers (CeO2, La2Zr2O7) and a superconducting layer (YBa2Cu3O7). In contrast to the production of many coated conductors in the international research community, a cheaper non-vacuum technique, namely the sol-gel method is used in this work. Every layer is produced starting from an aqueous precursor solution containing the corresponding metal acetates and an organic complexing agent, such as triethanolamine. The acidity of the solution was adjusted by adding ammonium hydroxide order to obtain a clear and stable gel without precipitation. Potentiometric titrations allowed us to determine the complexation behaviour of the metalions in the gel. Using the SUPERQUAD and EQUIL software, pH-distribution curves could be generated. Through dip-coating, thin films were deposited on the substrate. At low temperatures (60°C) the solution is transformed into an amorphous gel. The crystalline and biaxially textured buffer layers are formed during a heat treatment at elevated temperatures (1000°C) under inert atmosphere (Ar-5%H2). The superconducting film was deposited on a cleaned SrTiO3 substrate and heat treated at temperatures of 815°C under nitrogen with 200 ppm oxygen. Characterisation of the morphology and microstructure of the thin films were carried out using XRD, pole figures, SEM, AFM and TEM. The buffer layers show good in an out-of-plane alignment and a smooth surface with little impurities. The superconducting film has a critical temperature of 89 K and shows a sharp transition from normal to superconducting phase.

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Chicago
Cloet, Veerle, Jonas Feys, Serge Hoste, and Isabel Van Driessche. 2007. “Coated Conductor Synthesis Through Aqueous Sol-gel Chemistry.” In Sol-Gel, 14th International Conference, Abstracts.
APA
Cloet, V., Feys, J., Hoste, S., & Van Driessche, I. (2007). Coated conductor synthesis through aqueous sol-gel chemistry. Sol-Gel, 14th International conference, Abstracts. Presented at the 14th International Sol-Gel Conference (Sol-Gel 2007).
Vancouver
1.
Cloet V, Feys J, Hoste S, Van Driessche I. Coated conductor synthesis through aqueous sol-gel chemistry. Sol-Gel, 14th International conference, Abstracts. 2007.
MLA
Cloet, Veerle, Jonas Feys, Serge Hoste, et al. “Coated Conductor Synthesis Through Aqueous Sol-gel Chemistry.” Sol-Gel, 14th International Conference, Abstracts. 2007. Print.
@inproceedings{598617,
  abstract     = {High temperature superconductors such as YBa2Cu3O7 (Tc=92 K) can't be produced in long lengths because of their brittle ceramic nature. Another problem in using bulk YBCO is the absence of texture, biaxial texture is necessary to assure the quality of the superconductor. A solution to both problems is presented by the coated conductor structure. This structure consists of a flexible metallic tape (Ni-5at%W) coated with multiple buffer layers (CeO2, La2Zr2O7) and a superconducting layer (YBa2Cu3O7). In contrast to the production of many coated conductors in the international research community, a cheaper non-vacuum technique, namely the sol-gel method is used in this work. Every layer is produced starting from an aqueous precursor solution containing the corresponding metal acetates and an organic complexing agent, such as triethanolamine. The acidity of the solution was adjusted by adding ammonium hydroxide  order to obtain a clear and stable gel without precipitation. Potentiometric titrations allowed us to determine the complexation behaviour of the metalions in the gel. Using the SUPERQUAD and EQUIL software, pH-distribution curves could be generated. Through dip-coating, thin films were deposited on the substrate. At low temperatures (60°C) the solution is transformed into an amorphous gel. The crystalline and biaxially textured buffer layers are formed during a heat treatment at elevated temperatures (1000°C) under inert atmosphere (Ar-5%H2). The superconducting film was deposited on a cleaned SrTiO3 substrate and heat treated at temperatures of 815°C under nitrogen with 200 ppm oxygen.
Characterisation of the morphology and microstructure of the thin films were carried out using XRD, pole figures, SEM, AFM and TEM. The buffer layers show good in an out-of-plane alignment and a smooth surface with little impurities. The superconducting film has a critical temperature of 89 K and shows a sharp transition from normal to superconducting phase.},
  author       = {Cloet, Veerle and Feys, Jonas and Hoste, Serge and Van Driessche, Isabel},
  booktitle    = {Sol-Gel, 14th International conference, Abstracts},
  language     = {eng},
  location     = {Montpellier, France},
  title        = {Coated conductor synthesis through aqueous sol-gel chemistry},
  year         = {2007},
}