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
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 R...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 2 μm 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
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 films doped with different contents of gadolinium(Gd) were prepared by the low-fluorine(low-F)trifluoroacetate metal-organic deposition(MOD) method.The effects of flow rate and holding time of the firing(crystall...YBCO films doped with different contents of gadolinium(Gd) were prepared by the low-fluorine(low-F)trifluoroacetate metal-organic deposition(MOD) method.The effects of flow rate and holding time of the firing(crystallization) stage on the superconducting properties of YxGd1-xBa2 Cu3 O7-δ(YGdBCO) films were investigated.The phase formation and texture were characterized by the X-ray diffraction(XRD),which indicate that severe degradation of the microstructure will be induced with the inappropriate flow rate.The surface morphology and element distribution were investigated by the scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS).The results show that increasing the holding time of the firing stage is effective for the further decomposition of residual impurity phase on the surface.The mechanisms of the phase and surface evolution are also discussed.Finally,a high critical current density(Jc) value of 5.4 MA/cm2 was achieved in the Y0.9Gd0.1BCO film fabricated by the cooperative control of the flow rate and holding time of the firing stage,which are contributed to the formation of excellent texture,homogeneous microstructure and dense surface of the YGdBCO films.展开更多
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.
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 2 μm 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.
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Project supported by the National Natural Science Foundation of China (51577180,U1832131,51721005,51477168)the Youth Innovation Promotion Association of the Chinese Academy of Sciences (2016128)。
文摘YBCO films doped with different contents of gadolinium(Gd) were prepared by the low-fluorine(low-F)trifluoroacetate metal-organic deposition(MOD) method.The effects of flow rate and holding time of the firing(crystallization) stage on the superconducting properties of YxGd1-xBa2 Cu3 O7-δ(YGdBCO) films were investigated.The phase formation and texture were characterized by the X-ray diffraction(XRD),which indicate that severe degradation of the microstructure will be induced with the inappropriate flow rate.The surface morphology and element distribution were investigated by the scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS).The results show that increasing the holding time of the firing stage is effective for the further decomposition of residual impurity phase on the surface.The mechanisms of the phase and surface evolution are also discussed.Finally,a high critical current density(Jc) value of 5.4 MA/cm2 was achieved in the Y0.9Gd0.1BCO film fabricated by the cooperative control of the flow rate and holding time of the firing stage,which are contributed to the formation of excellent texture,homogeneous microstructure and dense surface of the YGdBCO films.
