Improved textured La2Zr2O7 buffer layers on bi-axially textured Ni–W substrates using CeO2 seed layers for YBa2Cu3O7 − x coated conductors

• La2Zr2O7 (LZO) films were firstly fabricated by magnetron sputtering.
• We firstly used the buffer architecture LZO/CeO2 (seed).
• We firstly fabricated YBa2Cu3O7 + x films directly on LZO films.

La2Zr2O7 (LZO) buffer layers were deposited on bi-axially textured Ni–W substrates with CeO2 seed layer by radio-frequency magnetron sputtering for the large-scale application of YBa2Cu3O7 − x (YBCO) coated conductors. The microstructure and surface morphology of LZO buffer layers were studied by X-ray diffraction, optical microscopy, field emission scanning electron microscopy and atomic force microscopy. The influences of substrate temperature and oxygen partial pressure on the microstructure and surface morphology of LZO buffer layers were discussed. It was found that epitaxial LZO films were preferentially c-axis oriented without microcracks, with no degradation of crystallographic texture and with high surface crystallinity. Crack-free and strong c-axis aligned LZO films with no random orientation were obtained at relatively low substrate temperatures of 600–800 °C and in flowing 40 Pa gas mixtures of Ar–O2 with an effective oxygen partial pressure of 0.1–20 Pa. In addition, LZO films grown in low oxygen partial pressure have a smoother surface than films in higher oxygen partial pressure. Then, we fabricated YBCO coated conductors on the high-quality LZO buffer layers by pulsed laser deposition. The critical current density Jc = 2.25 MA/cm2 and critical current Ic = 180 A/cm of 0.8-μm-thick YBCO film at 77 K, self field were obtained. The magnetic field and angular dependences of critical current per width were discussed. Highly textured LZO films grown on CeO2 seed layer were suitable as a buffer layer for the growth of YBCO coated conductors with high currents.