High-resolution electron microscopy of high-T c polycrystalline Nb3Ge fabrics

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Abstract
The fabric of high‐Tc Nb3Ge superconducting material synthesized by coevaporation in the vacuum has been investigated using 200‐kV high‐resolution electron microscopy. The grain texture deduced from the high‐resolution structure images, which consist of groups of small coaxial Nb3Ge grains (A15 structure) which have one cubic axis [001] in common, is observed and analyzed using the high‐resolution structure images. The coaxial grains are related by a rotation of approximately ±30° around the [001] axis. Crystallites of Nb5Ge3 composition having either a D88 structure or D8m structure are distributed at random in the fabric and are coherent with the adjacent Nb3Ge grains. The statistical distribution of grain sizes of each compound is reported. The average grain size of Nb5Ge3 compounds is smaller than half the average size of the Nb3Ge grains.