Single buffer layers of either Gd2Zr2O7 (GZO) or La2Zr2O7 (LZO) with different thickness on highly textured Ni-W tapes were compared with respective to the application of YBa2Cu3O7-δ coated conductors. The superconducting performances are improved as the buffer thickness of GZO or LZO increases up to a critical value, such as 310 and 240 nm, respectively. This suggests that a thin buffer layer is insufficient to prevent the Ni diffusion. If the buffer thickness increases further, the superconducting properties degrade, probably due to changes in the microstructure and degradation of the buffer texture. Comparing with LZO, the texture of GZO is hardly dependent on its thickness, due to smaller mismatch for its lattice with that of Ni-W. For both single buffered coated conductors, the superconducting transition temperatures are around 92 K with a transition width less than 1 K. Inductive measurement reveals that the critical current density (Jc) at 77 K in self-field, reaches 1.2 MA/cm2 and 0.77 MA/cm2 for GZO, and LZO, respectively. This implies that the single buffers of GZO and LZO are comparable to standard buffer architectures such as CeO2/YSZ/Y2O3 or CeO2/LZO, being promising for the process simplification and cost reduction.
Ying Liliang, Lu Yuming, Liu Zhiyong, Fan Feng, Gao Bo, Cai Chuanbing Shanghai University, Shanghai 200444, China
Iron-based superconductors namely Sr(Fe1.8Co0.2)As1.8 (FeAs1.8) and Sr(Fe1.8Co0.2)As1.85 (FeAs1.85) with As deficiency are prepared by solid-state reaction. X-ray diffraction reveals that the polycrystalline phase forms in the studied samples, identical to typical SrFe2As2 (122) matrix. Resistive and magnetic measurements show that the superconducting transition temperatures (Tc) are about 19 K for both FeAs1.8 and FeAs1.85. Compared with the performances of typical iron-based 122 superconductors arising from Co doping, the present samples show the suppressed superconductivity. Moreover, the antiferromagnetic (AFM) phase correlated with spin-density-wave (SDW) is reduced as well. The AFM transition temperature decreases to 122 K for FeAs1.85, while such a phase transition is absent at all for FeAs1.8, one sample with less As, implying that the existence of SDW and antiferromagnetism is more sensitive to As content.
Liu Zhiyong1, Lu Yuming1, Liu Jinlei1, Qu Chunqing1,2,3, Chen Changzhao1, Cai Chuanbing1, Huang Fuqiang3, Xie Xiaoming2 1 Shanghai University, Shanghai 200444, China
