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Chemical Solution Deposition of pyrochlore -type buffer layer of

Author: ShenYa
Tutor: ZhangGuoFang
School: Shaanxi Normal University
Course: Inorganic Chemistry
Keywords: HTS coated conductors The buffer layer Chemical solution deposition techniques Pyrochlore structure
CLC: TM26
Type: Master's thesis
Year: 2011
Downloads: 26
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Abstract

YBCO and BSCCO are working at liquid nitrogen temperature most practical high-temperature superconductors. Relative to the Bi-2223 superconductor, YBCO at 77 K under high field has better performance, so when the construction at 77 K or so when used in high-field magnets, YBCO strip is the preferred material. YBCO coated conductor is a multilayer composite film structure, with a metal base, a buffer layer, a superconducting layer and a protective layer. Was successfully prepared long HTS coated conductors with a buffer layer are used multilayer film structure, and are made of expensive physical vacuum deposition techniques. Currently expensive HTS coated conductors is impeding further practical bottleneck. For the buffer layer, the buffer layer material and a multi-functional exploration of low-cost chemical solution deposition (CSD) is considered to be a buffer layer for the future development goals. In this thesis, prepared by chemical solution deposition techniques pyrochlore-type rare-earth zirconate and molybdate films were studied in order to simplify the development of low-cost structure and the buffer layer coated conductor technology to provide experimental support for the preparation. Specific research papers are as follows: 1. Prepared using chemical solution deposition technique RE ₂ Zr ₂ O ₇ (RE = Nd, Sm) buffer layer using chemical solution deposition techniques (CSD-MOD) on YSZ single crystal substrates were prepared La2Zr2O7, Nd2Zr2O7, Sm2Zr2O7 and Gd2Zr2O7 film, in order to explore Nd2Zr2O7 and Sm2Zr2O7 HTS coated conductors as the possibility of a buffer layer, experiments were completely carried out under the same experimental conditions of. A component from the film, texture, surface morphology prepared above three aspects of the four films were compared and analyzed. The results confirm that, Nd2Zr2O7 and Sm2Zr2O7 with HTS coated conductors as a buffer layer potential. In order to examine Nd2Zr2O7 and Sm2Zr2O7 film as a buffer layer capacity, the use of cheap and efficient solution method in all YSZ / NZO and YSZ / SZO prepared to continue on the template layer and CeO2 lattice matched YBCO superconducting layer. YSZ / Nd ₂ Zr ₂ O ₇ / CeO ₂ / YBCO superconducting layer (006) diffraction peak rocking curve FWHM is 0.84 °, smooth and dense surface, without holes or cracks, a narrow transition temperature width △ Tc described for sample quality is better, the critical current density Jc = 0.8MA/cm ^{2 , It can be inferred Nd2Zr2O7 buffer layer is very promising. YSZ / Sm ₂ Zr ₂ O ₇ / CeO ₂ / YBCO superconducting layer (006) diffraction peak rocking curve FWHM is 3.02 °, the surface without holes or cracks, but the emergence of a crystal axis, the surface is not smooth and dense. Compared with Nd2Zr2O7 Sm2Zr2O7, Nd2Zr2O7 more suitable for use as a buffer layer. Having a biaxially textured Ni-5at% W metal baseband preparation Nd2Zr2O7 or Sm2Zr2O7 film is the ultimate goal of the experiment. Through optimization of the parameters of the heat treatment, the Ni-5at% W was prepared on a substrate film having a good orientation Nd2Zr2O7 optimum heat treatment as follows: room temperature to 300 ℃ temperature 1h and then heated to continue temperature 1000 ℃ 3h. Preparation of thin films with good orientation Sm2Zr2O7 better heat treatment process as follows: room temperature to 1000 ℃ thermostat 3h and then cooled naturally. Sample is always flowing Ar-4% H2 reducing atmosphere, the gas flow rate of 2.2 × 10-2 m · s-1. Also confirmed that the pyrochlore structure material as the buffer layer of practical thickness 60-70nm. (2) Preparation of chemical solution deposition technique RE ₂ Mo ₂ O ₇ (RE = Nd, Sm, Gd) buffer layer on Ni-5at% W metal substrate prepared with c-axis texture Nd2Mo207 film process: using neodymium acetylacetonate and aluminum acetylacetonate as precursor acid, methanol and propionic acid (volume ratio 3:2) mixed solvent prepared by total cation concentration precursor solution is 0.4M. The precursor solution was spin-coated on the metal Ni-5at% W alloy substrate, Ar-4% H2 atmosphere at a temperature of 350 ℃ after 1h precalciner crystallization temperature of 1000 ℃ 2h. Also proved by experiments: The use of such solvents acetylacetone against crystallization and orientation of the film growth. Prepared on the YSZ single crystal substrate having a c-axis texture Sm2M0207 film process: using acetylacetone samarium and molybdenum acetylacetonate as the precursor acid, methanol and propionic acid solvent volume ratio of 2:3 was prepared under the conditions of total cation concentration of the precursor solution of 0.4M, the precursor solution was spin-coated YSZ single crystal substrate, and an argon gas atmosphere temperature of 500 ℃ after 1h precalciner crystallization temperature of 1000 ℃ 2h. Similarly, the preparation of a single phase and has a c-axis Gd2M0207 texture Gd2M0207 film preparation process is as follows: the use of samarium acetylacetonate and molybdenum acetylacetonate as the precursor acid, methanol and propionic acid solvent volume ratio of 4:1 under the conditions Preparation of total cation concentration of the precursor solution of 0.4M, the precursor solution was spin-coated YSZ single crystal substrate, and an argon gas atmosphere temperature of 500 ℃ after 1h precalciner crystallization temperature of 1000 ℃ 2h. Also found through experiments: solvent ratio of mixed solvents and heat the atmosphere will affect the orientation of the film growth.}

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