Argonne National Laboratory

Materials Science

Theme II: Ionic Correlations and Lattice Strain

We study the impacts of ionic disorder and lattice strain upon properties in energy and strongly correlated electron materials.

Ionic Correlations in Fast Ion Conductors

The behavior of a broad range of energy technologies, including batteries, fuel cells, thermoelectricity devices, and relaxors is intrinsically coupled to ionic disorder. Our objective is to determine how short-range correlations affect fast ion conductivity. A detailed understanding of correlated diffusion is crucial for the rational design of new materials. To gain a deeper understanding, we utilize single-crystal diffuse and quasi-elastic neutron scattering in different fast ion conductors.

The structure of NaxV2O5 consists of V-O polyhedra that allow Na ions to occupy positions forming double-legged ladders (green spheres). The 3D-ΔPDF (top right) for diffuse scattering (bottom) shows that the Na ions form ordered zig-zag chains at low temperature, impacting their mobility (Nat. Mater.).

Lattice Strain in Strongly Correlated Oxides

Lattice correlations and elastic strain can impact phenomena, such as ferroelectric and quantum paraelectric states, metal-insulator transitions, or charge-ice states. These phenomena have mainly been attributed to strong electron correlations. We are utilizing single-crystal diffuse and inelastic neutron scattering to determine the presence of short-range lattice and nematic correlations and how they relate to materials properties in such systems.

Single-crystal diffuse X-ray scattering measurements from two samples of MoxVO2, both showing a sharp transition in the transport properties, reveal that short-range structural correlations are as important as long-range order in driving the transport properties (Phys. Rev. Lett.).