METHODS FOR PREPARING CRYSTALLINE FILMS
Methods of forming crystalline films on a substrate are provided. The crystalline films may be formed using amorphous nanoparticles. Methods of forming dispersions of amorphous nanoparticles are also provided.
1 . A process for making a crystalline film on a substrate comprising applying to the substrate amorphous nanoparticles and heating to cause the constituents of the amorphous nanoparticles to nucleate and grow on the substrate to form a crystalline film.
2 . The process of claim 1 , wherein the amorphous nanoparticles are applied to the substrate in a dispersion.
3 . The process of claim 2 , wherein the surface of the substrate exhibits a crystallographic structure, and wherein the growth of the crystalline film is epitaxial.
4 . The process of claim 2 , wherein the crystalline film comprises one or more metal oxides.
5 . The process of claim 4 , wherein the crystalline film comprises a perovskite.
6 . The process of claim 5 , wherein the crystalline film comprises a complex perovskite of the formula M a Q b Cu c O x , wherein
M is one or more metals selected from Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Fr, Tm, Yb, Lu and Bi,
Q is one or more Group IIa elements selected from Ca, Sr, Mg and Ba, and wherein
c=1-3,
a+b≧c,
a+b+c=3-8, and
x is a number to sufficient to satisfy the valence requirements of the other elements present.
7 . The process of claim 6 , wherein Q is Ba, Sr or both and in which b+c=2-3.
8 . The process of claim 5 , wherein the crystalline film comprises a complex perovskite of the formula YBa 2 Cu 3 O 7-δ , and wherein Y may be wholly or partially substituted with one or more of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Fr, Tm, Yb, Lu and Bi.
9 . The process of claim 1 , wherein the amorphous nanoparticles are formed by heating a mixture comprising a liquid and one or more organometallic compounds to decompose the one or more organometallic compounds, and wherein the crystalline film is a metal film.
10 . The process of claim 9 , wherein the amorphous nanoparticles are applied to the substrate in the form of a dispersion comprising the amorphous nanoparticles and a dispersion liquid, and wherein the amorphous nanoparticles are formed by heating one or more organometallic compounds and the dispersion liquid to decompose the one or more organometallic compounds.
11 . The process of claim 1 wherein the crystalline film is a metal oxide crystalline film having predetermined molar ratios of one or more metal oxides and having an average composition selected from the group consisting of M 2 Ba 2 CuO x , MBa 2 Cu 3 O x , MBa 2 Ca 2 Cu 3 O x , and Bi 2 Sr 2 CaCu 2 O x , and wherein the amorphous nanoparticles are produced by the steps of
(a) dissolving salts of M, Ba, Ca, Bi, Sr, and Cu in an organic solvent, in predetermined molar ratios proportional to the predetermined molar ratios of the metals in the metal oxide crystalline film; and
(b) heating the dissolved salts in the presence of an alcoholic solvent to a temperature at which amorphous nanoparticles are formed;
wherein M represents one or more metals selected from the group consisting of Hg, Tl, and the lanthanide elements, and x has a value between 4 and 9.
12 . The process of claim 11 , wherein the heating of the dissolved salts is accomplished by adding the solution of salts to a diol at a temperature in excess of 200° C.
13 . The process of claim 11 , wherein the crystalline film has an average composition selected from the group consisting of M 2 BaCuO x , and MBa 2 Cu 3 O x .
14 . The process of claim 13 , wherein the crystalline film has the average composition of YBa 2 Cu 3 O x .
15 . The process of claim 1 , wherein the amorphous nanoparticles have the same stoichiometry as the crystalline film to be formed.
16 . A process for forming a stable dispersion of amorphous nanoparticles comprising heating a mixture of a non-reactive solvent and organic salts of one or more metals to a temperature sufficient to cause the one or more organic metal salts to decompose into amorphous nanoparticles that are stably dispersed in the non-reactive solvent.
17 . The process of claim 16 , wherein the amorphous nanoparticles are formed from a metal oxide or a mixture of metal oxides.
18 . The process of claim 17 , wherein the amorphous nanoparticles are formed from a perovskite.
19 . The process of claim 18 , wherein the amorphous nanoparticles are formed from a complex perovskite of the formula M a Q b Cu c O x , wherein
M is one or more metals selected from Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Fr, Tm, Yb, Lu and Bi,
Q is one or more Group IIa elements selected from Ca, Sr, Mg and Ba, and wherein
c=1-3,
a+b≧c,
a+b+c=3-8, and
x is a number to sufficient to satisfy the valence requirements of the other elements present.
20 . The process of claim 19 , wherein Q is Ba, Sr or both and in which b+c=2-3.
21 . The process of claim 18 , wherein the amorphous nanoparticles are formed from a complex perovskite of the formula YBa 2 Cu 3 O 7-δ , and further wherein Y may be wholly or partially substituted with one or more of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Fr, Tm, Yb, Lu and Bi.
22 . The process of claim 16 , wherein the amorphous nanoparticles are applied to a substrate to form an epitaxial film, a crystalline non-epitaxial film, or other film, and wherein the amorphous nanoparticles and the film formed therewith have the same stoichiometry.
23 . A process for forming a metal oxide epitaxial film on a substrate comprising heating a mixture of a non-reactive solvent and at least one organometallic salt to decompose the at least one organometallic salt into amorphous nanoparticles that are stably dispersed in the non-reactive solvent, applying the dispersion of amorphous nanoparticles to the substrate that exhibits a crystallographic structure, and heating to cause the metal constituents of the amorphous nanoparticles to nucleate and grow on the substrate to form an epitaxial crystalline film.