Epitaxial films of sodium potassium tantalate (Na0.5K0.5TaO3, NKT) and sodium potassium niobate (Na0.5K0.5NbO3, NKN) were grown on single-crystal lanthanum aluminate (LAO) (100) (indexed as a pseudo-cubic unit cell) substrates via an all-alkoxide solution (methoxyethoxide complexes in 2-methoxyethanol) deposition route for the first time. X-ray diffraction studies indicated that the onset of crystallization in powders formed from hydrolyzed gel samples was 550 °C. 13C nuclear magnetic resonance studies of solutions of methoxyethoxide complexes indicated that mixed-metal species were formed, consistent with the low crystallization temperatures observed. Thermal gravimetric analysis with simultaneous mass spectrometry showed the facile loss of the ligand (methoxyethoxide) at temperatures below 400 °C. Crystalline films were obtained at temperatures as low as 650 °C when annealed in air. θ-2θ x-ray diffraction patterns revealed that the films possessed c-axis alignment in that only (h00) reflections were observed. Pole-figures about the NKT or NKN (220) reflection indicated a single in-plane, cube-on-cube epitaxy. The quality of the films was estimated via ω (out-of-plane) and φ (in-plane) scans and full-widths at half-maximum (FWHMs) were found to be reasonably narrow (∼1°), considering the lattice mismatch between the films and the substrate.

The innovative Combustion Chemical Vapor Deposition (CCVD) process is a non-vacuum technique that is being investigated to enable next generation products in several application areas including high-temperature superconductors (HTS). In combination with the Rolling Assisted Biaxially Textured Substrate (RABiTS) technology, the CCVD process has significant promise to provide low-cost, high-quality lengths of YBCO coated conductor. The CCVD technology has been used to deposit both buffer layer coatings as well as YBCO superconducting layers. A buffer layer architecture of strontium titanate and ceria have been deposited by CCVD on textured nickel substrates and optimized to appropriate thicknesses and microstructures to provide templates for growing PLD YBCO with high critical current density values. The CCVD buffer layers have been scaled to meter plus lengths with good epitaxial uniformity along the length. A short sample cut from one of the lengths enabled high critical current density PLD YBCO. Films of CCVD YBCO superconductors have been grown on single crystal substrates with critical current densities over 1 MA/cm2. Work is currently in progress to combine both the buffer layer and superconductor technologies to produce high-quality coupons of HTS tape made entirely by the non-vacuum CCVD process.

Chemical solution epitaxy was used to deposit an epitaxial film of Gd2O3 on roll-textured nickel. A 2-methoxyethanol solution of gadolinium methoxyethoxide was used for spin-coating and dip-coating. Films were crystallized using a heat treatment at 1160 °C for 1 h in 4% H2/96% Ar. Single-layer films were approximately 600 Å in thickness, and thicker films could be produced using multiple coatings. θ/2θ x-ray diffractograms revealed only (0041) reflections, indicating a high degree of out-of-plane texture. A pole-figure about the Gd2O3 (222) reflection indicated a single in-plane epitaxy. Scanning electron microscopy showed that the films were smooth, continuous, and free of pin holes. Atomic force microscopy revealed an average surface roughness of 53 Å. Electron diffraction indicated that the misalignment of the majority of the grains in the plane was less than 10°. High-current (0.4 MA/cm2) Yba2Cu3O7–δ films were grown on roll-textured nickel substrates using Gd2O3 as the base layer in a three-layer buffer structure.

Using solution chemistry, epitaxial films of rare-earth oxides of the general formula RE2O3 (where RE = Sm to Lu) were prepared on cubic-textured nickel tapes. Solutions of metal methoxyethoxides or metal acetate/methoxyethoxides in 2-methoxyethanol were used to coat rolltextured nickel tapes using either spin-coating or dip-coating. Coated tapes were subsequently heated in a reducing atmosphere at temperatures between 950 °C and 1160 °C for varying lengths of time. Film quality was determined using X-ray diffraction and electron and surface probe microscopy. Films were found to be oriented both in and out-of-plane of the substrate, free of pinholes and gross defects, and of sufficient quality for use as substrates for high Tc, superconductors.

Epitaxial films of lanthanum gallate, praseodymium gallate, and neodymium gallate were prepared on [100] strontium titanate and [100] lanthanum aluminate single crystal substrates using solution techniques. The solutions employed were mixed-metal methoxyethoxides in 2-methoxyethanol. Films were prepared by spin-coating with a partially hydrolyzed solution, followed by firing at 850 °C for 20 minutes in air. Theta/2-theta scans revealed only [h00] reflections and omega scans (rocking curves) indicated good out-of-plane orientation. Pole figures and phi scans revealed good in-plane orientation and a [100] || [100] epitaxial relationship between the film and the substrate.

Solution chemistry has been used to synthesize epitaxial films of SrLaGaO4, SrPrGaO4, SrLaAlO4, and SrPrAlO4 on single crystal substrates of [100] SrTiO3 and [100] LaAlO3. Precursor solutions were prepared from metal methoxyethoxides in 2-methoxyethanol. Films were prepared by spin-casting from partially hydrolyzed solutions followed by firing for 20 minutes in air at 850°C. The structure of the films was determined using X-ray diffraction. Theta/2-theta scans and omega scans (rocking curves) indicated that the films were c-axis aligned. Phi scans proved that the films were also aligned in-plane.

An all-alkoxide sol-gel process utilizing methoxyethoxide complexes in 2-methoxyethanol was used to prepare epitaxial films of SrBi2Nb2O9, SrBi2Ta2O9, BaBi2Nb2O9, BaBi2Ta2O9, and Bi4Ti3O12 on [100] oriented SrTiO3 single crystals. Films were prepared by spin coating strontium titanate substrates with partially hydrolyzed alkoxide solutions and firing in air at 850 °C for 20 minutes. Out-of-plane orientation was confirmed by θ-2θ scans which showed only [002ℓ] reflections. In-plane orientation was determined by pole figures and phi-scans about the [105] plane in the case of the (Sr,Ba)Bi2(Nb,Ta)2O9 complexes and the [117] plane in the case of Bi4Ti3O12. Lattice constants and full-width at half-maximum (fwhm) values for both in-plane and out-of-plane reflections are reported.

Cubic rare-earth aluminate perovskites of the general form REAIO3 have been identified as possible buffer layers for high current carrying cuprate superconductors deposited on roll-textured metals. This paper describes on-going research to develop solution routes which would avoid the use of slow and costly vacuum processing. Our research plan includes the development of an appropriate solution chemistry, studies of the crystallization behavior of powders under reducing and oxidizing conditions, deposition of polycrystalline films on silver substrates, deposition of epitaxial films on single-crystal oxide substrates, and deposition on roll textured nickel. The method is illustrated with the example of PrAlO3.