Microstructure Characterization of Nb₃Sn Wires With Nanoprecipitate Artificial Pinning Centers Using Synchrotron High-Energy X-Rays

Synchrotron high-energy X-rays were used in an attempt to estimate nanoprecipitate size and size distribution in Nb3Sn powder-in-tube wires with ZrO2 or HfO2 artificial pinning centers via small angle X-ray scattering (SAXS). The effect of sample preparation was studied but measurements for as-received and for partially etched wires were not successful. Extracted sub-elements appeared to show more scattering contrast due to the lower number of phases, but no particle size could be extracted in this first attempt. Analysis of TEM data from the literature showed large particle size distribution (PSD) for different heat treatment conditions, suggesting that PSD could likely never be measured with SAXS due to a smeared signal. Experimental challenges with in-situ measurements revealed the sensitivity of infra-red furnaces and to changes in sample emissivity. The use of in-situ wide angle X-ray scattering data was successful in estimating the wire temperatures from the lattice parameter of copper and could be used in future heat treatment studies to better understand tin oxide dissolution.