YBa2Cu3O7-x（YBCO） films with co-doping BaTiO3（BTO） and Y2O3 nanostructures were prepared by metal organic deposition using trifluoroacetates（TFA-MOD）. The properties of the BTO/Y2O3co-doped YBCO films with different excess yttrium have been systematically studied by x-ray diffraction（XRD）, Raman spectra, and scanning electron microscope（SEM）. The optimized content of yttrium excess in the BTO/Y2O3co-doped YBCO films is 10 mol.%, and the critical current density is as high as - 17 mA/cm^2（self-field, 65 K） by the magnetic signal. In addition, the Y2Cu2O5 was formed when the content of yttrium excess increases to 24 mol.%, which may result in the deterioration of the superconducting properties and the microstructure. The unique combination of the different types of nanostructures of BTO and Y2O3 in the doped YBCO films, compared with the pure YBCO films and BTO doped YBCO films, enhances the critical current density（JC） not only at the self-magnetic field, but also in the applied magnetic field.
YBaCuO(YBCO) films with co-doping of Ba Ti O(BTO) and YOnanostructures were successfully fabricated on La Al O(LAO) substrate by metal organic deposition using trifluoroacetates(TFA-MOD). The focus of this study was to optimize the process conditions during the firing heat treatment of high critical current density(J C)-co-doped YBCO films. The effect of the firing temperatures on both the surface morphology and the superconducting properties for the doped YBCO films was systematically studied. According to the X-ray diffraction(XRD) and scanning electron microscopy(SEM) results,the films prepared at 820 and 850 °C show poor electrical performance due to impurity phases and large pores. In contrast, the dense YBCO films prepared at 830 and840 °C with the critical current densities of 10 MA-cm(77 K, 0 T) are obtained.
YBa2Cu3O7-x （YBCO） films with embedded BaZrO3 and BaTiO3 nanoparticles were fabricated by metalorganic deposition using trifluoroacetates （TFA-MOD）. Both X-ray diffraction and transmission electron microscopy revealed that these BaZrO3 and BaTiO3 nanoparticles had random orientations and were distributed stochastically in the YBCO matrix. The unique combined microstructure enhances the critical current density （Jc） of the BaZrO3/BaTiO3 doped-YBCO films, while keeping the critical transition temperature （Tc） close to that in the pure YBCO films. These results indicate that BaZrO3 and BaTiO3 nanoparticles provide strong flux pinning in YBCO films.
Aluminum-doped zinc oxide （ZnO：AI） films were deposited by direct current magnetron sputtering in incorporating hydrogen in sputtering gas at room temper- ature. The influences of hydrogen content in sputtering gas on the structural, optical, and electrical properties of ZnO：A1 films were systematically investigated. It is found that hydrogen incorporated into ZnO lattice forms shallow donors in ZnO：A1 films and plays an important role in the properties of ZnO：A1 films. The electrical conductivity and infrared （IR） reflectance are improved due to the increase of electron carrier concentration, and the average trans- mittance decreases, which is ascribed to the strong scat- tering from the hydrogen incorporated and oxygen vacancies in ZnO：A1 films. In this study, the resistivity of 5.5 × 10-4 Ω.cm is obtained, the average transmittance of the wavelength in the range of 400-900 nm is almost 86 %, and the IR reflectance reaches 75 % at 2,500 nm, which is higher than that of reported TCO films. The band gap determined by optical absorption is a result of com- petition between Burstein-Moss effect and many-body perturbation effect. However, the hydrogen content in sputtering gas is above 10 %, and the optical band gap shift is independent of hydrogen content in sputtering gas.
Fei QuTeng ZhangHong-Wei GuQing-Quan QiuFa-Zhu DingXing-Yu PengHong-Yan Wang
In this study, BaTiO3 （BTO）-doped YBCO films are prepared on LaA103 （100） single-crystal substrates by metal- organic decomposition （MOD） using trifluoroacetate （TFA） precursor solutions. The critical current density （Jc） of BTO/YBCO film is as high as 10 MA/cm2 （77 K, 0 T）. The BTO peak is found in the X-ray diffraction （XRD） pattern of a final YBCO superconductivity film. Moreover, a comprehensive study of the precursor evolution is conducted mainly by X-ray analysis and μ-Raman spectroscopy. It is found that the TFA begins to decompose at the beginning of the thermal process, and then further decomposes as temperature increases, and at 700 ℃ BTO nanoparticles begin to appear. It sug- gests that the YBCO film embedded with BTO nanoparticles, whose critical current density （Jc） is enhanced, is successfully prepared by an easily scalable chemical solution deposition technique.
We report the thickness dependence of critical current density （Jc） in YBa2Cu3O7-x （YBCO） films with BaZrO3 （BZO） and Y2O3 additions grown on single crystal LaAlO3 substrates by metalorganic deposition using trifluoroacetates （TFA-MOD）. Comparing with pttre YBCO films, the Jc of BZO/Y2O3-doped YBCO films was significantly enhanced. It was also found that with the increase of the thickness of YBCO film from 0.25 μm to 1.5 μm, the Ic of BZO/Y2O3-doped YBCO film increased from 130 A/cm to 250 A/cm and yet Jc of YBCO film decreased from 6.5 MA/cm2 to 2.5 M A/cm2. The thick BZO/Y2O3-doped MOD-YBCO film showed lower Jc, which is mainly attributed to the formation of a-axis grains and pores.
