Several types of REBa2Cu3O7-x （REBCO, RE=Y, Ho etc.） films are prepared on single crystal substrate LaAIO3 by TFA-MOD method. The phase transformation and optimized growth conditions in the crystallization are studi...Several types of REBa2Cu3O7-x （REBCO, RE=Y, Ho etc.） films are prepared on single crystal substrate LaAIO3 by TFA-MOD method. The phase transformation and optimized growth conditions in the crystallization are studied. Compared with SmBCO and GdBCO, high quality YBCO and HoBCO films are relatively easy to produce. It is revealed that the YBCO grains can form at low temperatures such as 730 ℃ during the initial heating ramp. With a high heating rate of 20 K/min and a low oxygen pressure of 100 ppm, the optimum growth temperature is around 780℃, at which the films show a Jc value of 2.88 MMcm2. Further decrease of the heating rate may produce the highquality YBCO Film with a higher Jc of 3.65 MA/cm2. The temperature dependence of resistances in various magnetic fields up to 9 T shows that the present TFAMOD YBCO and HoBCO films have similar superonducting transition temperature and magnetotransport properties.展开更多
Epitaxial YBCO superconducting films were deposited on the single crystal LaAlO3 （001） substrate by metal organic deposition method. All YBCO films were fired at 820 ℃ in humidity range of 2.6%-19.7% atmosphere. Mi...Epitaxial YBCO superconducting films were deposited on the single crystal LaAlO3 （001） substrate by metal organic deposition method. All YBCO films were fired at 820 ℃ in humidity range of 2.6%-19.7% atmosphere. Microstructure of YBCO thin films was analyzed by means of X-ray diffraction （XRD） and scanning electron microscopy （SEM）. Superconducting properties of YBCO films were measured by four-probe method. XRD results showed that the second phase （such as BaF2）and a-axis-oriented grains existed in the films prepared at 2.6% humidity condition; a-axis-oriented grains increased in the film prepared at higher than 4.2% humidity condition; almost pure c-axias-oriented grains existed in the films fired at 4.2% humidity condition. Morphologies of the YBCO films showed that all films had a smooth and crack-free surface. YBCO film prepared at 4.2% humidity condition showed Jc value of 3.3 MA/cm^2 at 77 K in self-field.展开更多
Epitaxial YBCO films were deposited on （100） LaAlO3 single-crystal substrates by metalorganic deposition of metal trifluoroacetate precursors with different concentrations. All the YBCO films have Tc around 91 K and...Epitaxial YBCO films were deposited on （100） LaAlO3 single-crystal substrates by metalorganic deposition of metal trifluoroacetate precursors with different concentrations. All the YBCO films have Tc around 91 K and Jc excess 2 MA/cm^2 at 77 K in zero field. XRD θ-2θscans show all the films have c-axis normal orientation. The FWHM （full width at half-maximum intensity） values of X-ray ω-scans of （005） reflection are 0.379°, 0.283°, and 0.543° for the YBCO thin films deposited with precursor solution concentrations of 1.52, 1.0, and 0.75 mol/L, respectively. With the concentration of the precursors decreasing, the thickness of the films decreases linearly. SEM micrographs show that porosities in the films become bigger with the precursor solution concentration decreasing. The big porosities in the film with the lowest concentration precursor deteriorate the superconducting property and make it have a wider superconducting transition and a lower Jc.展开更多
YBCO high temperature coated conductors are the most promising candidate for large scale superconducting transmission cables and fault current limiters.A modified TFA-MOD method was applied to prepare YBCO layer on Ro...YBCO high temperature coated conductors are the most promising candidate for large scale superconducting transmission cables and fault current limiters.A modified TFA-MOD method was applied to prepare YBCO layer on Rolling Assisted Biaxially Textured Substrate(RABiTS)with textured Y 2 O 3/YSZ/CeO 2 buffer layers,resulting in reduced time and cost of fabrication.By using Cu naphthenate instead of Cu(TFA)2,the pyrolysis time of the YBCO precursors was reduced significantly.YBCO films with thickness of 2μm were fabricated with multiple-coating and annealed at high temperature for 2 h.X-ray diffraction analysis revealed that the films were c-axis oriented.The preliminary results of YBCO films yielded 0.2 MA/cm 2 at 77 K and self field.It is believed current carrying ability of YBCO films could be further improved by reducing the reaction rate at the interface between the buffer layer and superconducting layer.展开更多
基金This work was supported by the National Natural Science Foundation of China under Grant No. 50672057, 50702033 and 10774098the National Science Foundation of China (973 Projects) under Grant No. 2006CB601005+1 种基金the Science and Technology Commission of Shanghai Municipality under Grant No. 0752nm017the Project Based Personnel Exchange Program between China and Germany under Grant No. [2006] 3139.
文摘Several types of REBa2Cu3O7-x （REBCO, RE=Y, Ho etc.） films are prepared on single crystal substrate LaAIO3 by TFA-MOD method. The phase transformation and optimized growth conditions in the crystallization are studied. Compared with SmBCO and GdBCO, high quality YBCO and HoBCO films are relatively easy to produce. It is revealed that the YBCO grains can form at low temperatures such as 730 ℃ during the initial heating ramp. With a high heating rate of 20 K/min and a low oxygen pressure of 100 ppm, the optimum growth temperature is around 780℃, at which the films show a Jc value of 2.88 MMcm2. Further decrease of the heating rate may produce the highquality YBCO Film with a higher Jc of 3.65 MA/cm2. The temperature dependence of resistances in various magnetic fields up to 9 T shows that the present TFAMOD YBCO and HoBCO films have similar superonducting transition temperature and magnetotransport properties.
基金supported by the National 863 Program of Ministry of Science and Technology of China (2007AA03Z216)
文摘Epitaxial YBCO superconducting films were deposited on the single crystal LaAlO3 （001） substrate by metal organic deposition method. All YBCO films were fired at 820 ℃ in humidity range of 2.6%-19.7% atmosphere. Microstructure of YBCO thin films was analyzed by means of X-ray diffraction （XRD） and scanning electron microscopy （SEM）. Superconducting properties of YBCO films were measured by four-probe method. XRD results showed that the second phase （such as BaF2）and a-axis-oriented grains existed in the films prepared at 2.6% humidity condition; a-axis-oriented grains increased in the film prepared at higher than 4.2% humidity condition; almost pure c-axias-oriented grains existed in the films fired at 4.2% humidity condition. Morphologies of the YBCO films showed that all films had a smooth and crack-free surface. YBCO film prepared at 4.2% humidity condition showed Jc value of 3.3 MA/cm^2 at 77 K in self-field.
文摘Epitaxial YBCO films were deposited on （100） LaAlO3 single-crystal substrates by metalorganic deposition of metal trifluoroacetate precursors with different concentrations. All the YBCO films have Tc around 91 K and Jc excess 2 MA/cm^2 at 77 K in zero field. XRD θ-2θscans show all the films have c-axis normal orientation. The FWHM （full width at half-maximum intensity） values of X-ray ω-scans of （005） reflection are 0.379°, 0.283°, and 0.543° for the YBCO thin films deposited with precursor solution concentrations of 1.52, 1.0, and 0.75 mol/L, respectively. With the concentration of the precursors decreasing, the thickness of the films decreases linearly. SEM micrographs show that porosities in the films become bigger with the precursor solution concentration decreasing. The big porosities in the film with the lowest concentration precursor deteriorate the superconducting property and make it have a wider superconducting transition and a lower Jc.
基金National Science Foundation of China(51002024)"863"High-Tech Project(2007AA03Z201)
文摘YBCO high temperature coated conductors are the most promising candidate for large scale superconducting transmission cables and fault current limiters.A modified TFA-MOD method was applied to prepare YBCO layer on Rolling Assisted Biaxially Textured Substrate(RABiTS)with textured Y 2 O 3/YSZ/CeO 2 buffer layers,resulting in reduced time and cost of fabrication.By using Cu naphthenate instead of Cu(TFA)2,the pyrolysis time of the YBCO precursors was reduced significantly.YBCO films with thickness of 2μm were fabricated with multiple-coating and annealed at high temperature for 2 h.X-ray diffraction analysis revealed that the films were c-axis oriented.The preliminary results of YBCO films yielded 0.2 MA/cm 2 at 77 K and self field.It is believed current carrying ability of YBCO films could be further improved by reducing the reaction rate at the interface between the buffer layer and superconducting layer.
