Micromechanical Property Evaluation Of REBCO Coated Conductors Using Microcantilever Beam Method

Abstract

REBCO coated conductor (CC) has been applied to high field magnets due to its high critical current density (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) and high tensile strength. In order to further improve in-field critical current density (Jc), we have developed EuBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Oy (EuBCO) CCs doped with BaHfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (BHO) as artificial pinning centers (APCs). Although it is important for conductor development to understand the difference in mechanical properties depending on the REBCO materials, it was difficult to directly measure the strength and fracture toughness of the superconducting layer in the CCs. As a new approach, we introduced the microcantilever beam method to evaluate the micromechanical properties of the superconducting layer. The microcantilever beam specimens (~μm) were formed in the superconducting layer by focused ion beam (FIB) processing. Their strengths were measured by bending tests using a nanoindenter. We report on details of the test method and a comparison of the strength of the CCs.