Process for the production of highly-textured, band-shaped, high-temperature superconductors
A wet-chemical method for producing strip-shaped high-temperature superconductors with a substrate, optionally with a buffer layer and with a high-temperature superconductive layer is improved by increasing the texturing and the layer thickness of the high-temperature superconductive layer. To this end, precursor solutions are applied in layers to the substrate, of which the first is low in fluorine or does not contain fluorine, and the following have a fluorine concentration that increases with each layer.
1. A process of forming a band-shaped high temperature superconductor including a metal substrate and a high temperature superconductor layer (HTSL) having a multi-layer architecture formed of at least two precursor layers, the process comprising:
(a) forming a first precursor solution comprising a first solvent;
(b) applying the first precursor solution to the metal substrate;
(c) drying and pyrolyzing the first precursor solution to form a first superconductor precursor layer;
(d) forming a second precursor solution comprising a second solvent;
(e) applying the second precursor solution to the first superconductor precursor layer;
(f) drying and pyrolyzing the second precursor solution to form a second superconductor precursor layer; and
(g) thermally treating the precursor layers to form the HTSL,
wherein a fluorine concentration of the first precursor solution is less than a fluorine concentration of the second precursor solution.
2. The process of claim 1 further comprising applying a third precursor solution including a third solvent, wherein the third precursor solution possesses a higher fluorine concentration than the first and second precursor solutions.
3. The process of claim 2 , wherein the first precursor layer is essentially fluorine free.
4. The process of claim 2 , wherein at least one of the the first, second, and third solvent is selected from the group consisting of propionic acid, pivalic acid, methanol, and toluene.
5. The process of claim 1 , wherein the heat treatment (f) is carried out at temperatures below the melting point of the HTSL.
6. The process of claim 1 , wherein the first precursor solution comprises a compound selected from the group consisting of Y(III)-trimethyl acetate, Ho(III)-trimethyl acetate, Cu(II)-trimethyl acetate, and barium hydroxide-octahydrate.
7. The process of claim 1 , wherein the second precursor solution comprises trifluoroacetic acid.
8. The process of claim 1 , wherein the second precursor solution comprises trifluoroacetate.
9. The process of claim 1 , wherein:
the second precursor solution comprises YBCO; and
the second precursor solution comprises less than about 6 mol of fluorine per mol of YBCO.
10. The process of claim 1 , wherein:
the second precursor solution comprises YBCO; and
the second precursor solution comprises at least 30 mol of fluorine per mol of YBCO.
11. The process of claim 1 , wherein at least one buffer layer is applied to the substrate before the first precursor solution is applied.
12. A process for the production of band-shaped HTSL including a metal substrate, at least one buffer layer, and an HTSL located on the buffer layer, the process comprising:
(a) producing a coating solution comprising a polar solvent with at least one free hydroxyl group;
(b) applying the coating solution to the metal substrate;
(c) drying the coating solution;
(d) forming a buffer layer by annealing the dried coating solution;
(e) providing a first precursor solution comprising a first precursor solvent;
(f) applying the first precursor solution to the buffer layer;
(g) drying and pyrolyzing the first precursor solution to form a first superconductor precursor layer;
(h) providing a second precursor solution comprising a second precursor solvent;
(i) applying the second precursor solution to the first precursor layer;
(j) drying and pyrolyzing the second precursor solution to form a second superconductor precursor layer; and
(k) thermally treating the precursor layers to form the HTSL,
wherein the fluorine concentration of the first precursor solution is less than the fluorine concentration of the second precursor solution, and wherein the fluorine content of the resulting first superconductor precursor layer is less than the fluorine content of the resulting second superconductor precursor layer.
13. The process of claim 12 , wherein the polar solvent comprises a carboxylic acid.
14. The process of claim 13 , wherein the carboxylic acid comprises propionic acid.
15. The process of claim 12 , wherein the coating solution further comprises at least one compound selected from the group consisting of a zirconium compound, a lanthanum compound, and a rare earth compound.
16. The process of claim 15 , wherein:
the zirconium compound comprises zirconium(IV) 2,4-pentadionate;
the lanthanum compound comprises lanthanum(III) 2,4-pentadionate; and
the rare earth compound is selected from the group consisting of cerium(III) acetylacetonate, Gd(III) acetylacetonate, and yttrium(III) 2,4-pentadionate.
17. The process of claim 12 , wherein the substrate comprises a textured, non-ferromagnetic metal band.
18. The process of claim 17 , wherein the metal band comprises a Ni-Wo alloy or a Ni—Mn alloy.
19. The process of claim 12 further comprising (l) applying a functional metal layer to the HTSL.
20. A process of forming a band-shaped HTSL, the process comprising:
(a) applying a first precursor solution to a metal substrate;
(b) treating the first precursor solution to form a first superconductor precursor layer;
(c) applying a second precursor solution to the first precursor layer;
(d) treating the second precursor solution to form a second superconductor precursor layer, wherein the first superconductor precursor layer possesses a lower concentration of fluorine than the second superconductor precursor layer; and
(e) thermally treating the layers to form the HTSL, wherein the formed HTSL possesses a multilayer architecture defined by the superconductor precursor layers.
21. The process of claim 20 , wherein the first superconductor precursor layer is fluorine free.
22. The process of claim 21 , wherein:
(b) comprises (b.1) drying the first precursor solution and (b.2) pyrolyzing the first precursor solution to form the first superconductor precursor layer; and
(d) comprises (d.1) drying the second precursor solution and (d.2) pyrolyzing the second precursor solution to form the second superconductor precursor layer.
23. The process of claim 20 wherein:
the process further comprises:
(f) applying a buffer solution to the metal substrate, and
(g) treating the buffer solution form a buffer layer; and
(a) comprises (a.1) applying the first precursor solution to the buffer layer.
24. The process of claim 23 , wherein the buffer solution comprises a polar solvent with at least one free hydroxyl group.
25. The process of claim 20 , wherein (d) further comprises applying a third precursor solution to the second superconductor precursor layer and treating the third precursor solution to form a third superconductor precursor layer, wherein the third superconductor precursor layer possesses a higher concentration of fluorine than the first and second superconductor precursor layers.