Byeong-Joo Kim

Optimization of processing parameters of YBCO films prepared by a dichloroacetic-metalorganic deposition method

The fluorine-free dichloroacetic-metalorganic deposition (DCA-MOD) method has been optimized and high-Jc YBa2Cu3Ox (YBCO) superconducting films over 1 MA cm−2 have been obtained. The effects of using a dilution solvent for the preparation of coating solutions were investigated for methanol and 2-methoxyethanol, respectively. The uniformity of the film thickness was improved by the use of 2-methoxyethanol. The two-step heat treatment for the preparation of the YBCO film led to a significant densification of the microstructure. Coated films were calcined at lower temperatures of up to 500 °C in a flowing oxygen atmosphere with a humidity of 7.2%. Conversion heat treatment was performed at various temperatures of 780–810 °C for 2 h in flowing Ar gas containing 1000 ppm oxygen with a humidity of 9.45%. SEM observations showed that the films have very dense microstructures with little pores. X-ray diffraction analysis showed that YBCO grains grew with a (00l) preferred orientation. A high critical current density (Jc) of 1.28 MA cm−2 (at 77 K and self-field) was obtained for the YBCO film prepared by the two-step heat treatment.

Deposition of YBCO Thin Film by Aerosol Assisted Spray Pyrolysis Using Nitrates

Coated conductor by MOCVD shows the best Ic × L performance currently, but cost reduction is still ongoing issue. R&D effort for a process capable of utilizing cheap alternative precursors were tried by many research groups but few of them showed results having potential for replacing current MOCVD. Spray pyrolysis method adopting ultrasonic atomization was tried as one of the possible options. Y123 films have been deposited on LaAlO3 (100) single-crystal and IBAD substrates by aerosol assisted spray pyrolysis method. Ultrasonic atomization was used in order to generate fine droplets of precursor solution made of Y, Ba, Cu nitrate. A pre-heater was located between spraying nozzle and substrate for fast drying and enhancing decomposition of precursors. SEM and XRD observation revealed that deposited films have smooth and dense microstructure. The influence of operating parameters such as cation stoichiometry, oxygen partial pressure, substrate temperature on the microstructure, formation of superconducting 123 phases and superconducting properties of deposited films were tested. Ex-situ conversion was tried to decrease the possible reactions between precursor compounds and buffer layer materials of metal substrate showed the possibility of adopting this technique for epitaxial growth of 123 phase on metal substrate.