Use of neutron diffraction to determine grain-size effects on strain in YBa{sub 2}CU{sub 3}O{sub 7-x}

Abstract

Anisotropic expansion and contraction of YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) grains during fabrication could lead to internal stresses that may be relieved by microcracking, resulting in low strength and critical current density. Neutron diffraction techniques have been used to examine the internal strain distribution as a function of grain size in YBCO samples. The full width at half maximum (FWHM) of the Gaussian shaped diffraction peaks is used for strain distribution analysis. The FWHM of the strain distribution for coarse-grain YBCO is found to be about 0.05%, while that for fine-grain material is significantly higher at about 0.3%. Results of this study suggest that the strains are relieved by microcracking in coarse-grain YBCO.