Nanosized rare-earth hexaborides: Low-temperature preparation and microstructural analysis

•A synthesis of nanosized rare-earth-hexaboride (REB6) was developed.•Rare-earth hexaborides could be used as overdopants in MgB2 superconductors.•All compounds were characterized by XRPD and SEM methods.•A microstructural analysis (DFA) afforded the nanocrystal size distributions.

A versatile, rapid and easy synthesis of pure rare-earth-(RE) hexaboride powders was developed, without resorting to hazardous precursors or generating undesired, ineliminable, side products. To this purpose, we employed a metathesis reaction, typically starting from a mixture of a hydrated rare earth trichloride and MgB2, kept at 650 °C for 1 h under vacuum. This methodology affords nanosized RE hexaborides, with average crystallite (domain) sizes down to a few nanometers, useful for tailoring the functional performances of the MgB2 superconducting phase produced by the reactive liquid infiltration method. For the powders showing the lowest average domain sizes (YbB6 and EuB6), an unconventional microstructural analysis, based on Total Scattering methods and on the Debye Function Approach, was also performed, which provided the complete nanocrystal size distributions.

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