Epitaxial vanadium nanolayers to suppress interfacial reactions during deposition of titanium-bearing Heusler alloys on MgO(001)

Description of the dataset (a brief outline of the nature and purpose of the dataset)

An in-situ approach for preparing atom probe tomography specimens by xenon plasma-focused ion beam

A method for the rapid preparation of atom probe tomography (APT) needles using a xenon plasma-focussed ion beam (FIB) instrument is presented and demonstrated on a test sample of Ti-6Al-4V alloy. The method requires significantly less operator input than the standard lift-out protocol, is site-specific and produces needles with minimal ion-beam damage; electron microscopy indicated the needle's surface amorphised/oxidised region to be less than 2 nm thick. The resulting needles were routinely analysable by APT, confirming the expected microstructure and showing negligible Xe contamination

A correlative study of interfacial segregation in a Cu-doped TiNiSn thermoelectric half-Heusler alloy

Funding: The LEAP 5000XR at Oxford is supported by EPSRC grant EP/M022803/1. The P-FIB UXe DualBeam FIB/SEM at Glasgow is supported by EPSRC grant EP/P001483/1, and the EPSRC is also acknowledged for funding the work on nanostructured half-Heuslers for thermoelectric waste heat recovery (grants EP/N01717X/1 and EP/N017218/1) and a studentship (grant EP/N509668/1).The performance of thermoelectric materials depends on both their atomic-scale chemistry and the nature of microstructural details such as grain boundaries and inclusions. Here, the elemental distribution throughout a TiNiCu0.1Sn thermoelectric material has been examined in a correlative study deploying atom-probe tomography (APT) and electron microscopies and spectroscopies. Elemental mapping and electron diffraction reveal two distinct types of grain boundary that are either topologically rough and meandering in profile or more regular and geometric. Transmission electron microscopy studies indicate that the Cu dopant segregates at both grain boundary types, attributed to extrusion from the bulk during hot-pressing. The geometric boundaries are found to have a degree of crystallographic coherence between neighboring grains; the rough boundaries are decorated with oxide impurity precipitates. APT was used to study the three-dimensional character of rough grain boundaries and reveals that Cu is present as discrete, elongated nanoprecipitates cosegregating alongside larger substoichiometric titanium oxide precipitates. Away from the grain boundary, the alloy microstructure is relatively homogeneous, and the atom-probe results suggest a statistical and uniform distribution of Cu with no evidence for segregation within grains. The extrusion suggests a solubility limit for Cu in the bulk material, with the potential to influence carrier and phonon transport properties across grain boundaries. These results underline the importance of fully understanding localized variations in chemistry that influence the functionality of materials, particularly at grain boundaries.Publisher PDFPeer reviewe