Numerical analysis of the influence of buffer layer thickness on the residual stresses in YBCO/La2Zr2O7/Ni superconducting materials

The present paper addresses a numerical investigation of the influence of buffer layer thickness on the residual stress in YBCO/La2Zr2O7/Ni architectured materials under cryogenic conditions by using classical lamination theory (CLT) and finite element method (FEM) for coated conductor applications. YBCO/La2Zr2O7 multilayer films were fabricated on Ni tape substrate using reel-to-reel sol–gel and pulse laser deposition (PLD) systems. The microstructural evolution of high temperature superconducting YBCO film and buffer layers with La2Zr2O7 configuration grown on textured Ni tape substrates was investigated by using a scanning electron microscope (SEM). Thermal stress analysis of YBCO/La2Zr2O7/Ni multilayer sample was performed by using CLT in the temperature range of 298–175 K in liquid helium media. The YBCO/La2Zr2O7/Ni sample strip was solved by using FEM for linear or nonlinear cases in the temperature range of 298–3 K in liquid helium media. SEM observations revealed that crack-free, pinhole-free, continuous superconducting film and buffer layer were obtained by sol–gel and PLD systems. In addition to microstructural observations, it was found that the largest compressive stresses and failure occur in La2Zr2O7 buffer layer due to its smallest thermal expansion coefficient. The thickness of La2Zr2O7 buffer layer affects the failure. The stress component of σx is the smallest in Ni tape substrate due to its largest thickness.