Research Interests

Negative Thermal Expansion (NTE) Materials: Most materials expand as they are heated, but there is a small and growing group of compounds that shrink on heating (display negative thermal expansion). Such materials are of potential use in composites as blending both negative and positive thermal expansion compounds provides a way of tailoring the thermal expansion characteristics of the resulting material. Being able to tailor the thermal expansion characteristics is useful as there are many applications where either zero thermal expansion is desirable (e.g. optical devices where accurate positioning is crucial) or there is a need to match the thermal expansion coefficients of two parts that are bonded together. We have developed a synthetic method for the preparation of a new NTE material cubic ZrMo₂O₈ and we are currently investigating both the details of it physical properties and methods for tailoring the thermal expansion characteristics of this material and some of its relatives.

Clathrate Thermoelectric Materials: Thermoelectric devices can be used to provide electrical power from a temperature difference or to produce a temperature difference when supplied with electrical power. There is considerable interest in developing new materials that would facilitate the replacement of current refrigeration technology with efficient all solid-state thermoelectric devices. One attractive candidate family of materials are the so called clathrates. They have 3D covalently bonded frameworks of atoms such as Si, Ge or Sn with species such as Cs, Rb, K, Na, Sr, or Eu vibrating inside cavities in the framework. The disorder associated with the vibrational motion of the species in the cavities and any disorder in the framework that is introduced by doping has a large impact on their thermoelectric properties. We are currently exploring the occurrence and importance of disorder in clathrate thermoelectric materials in collaboration with researchers at Renslaer Polytechnic Institute and Marlow Industries.

New Applications of Synchrotron X-ray Methods: We are interested in further developing the use of synchrotron X-ray diffraction methods for the characterization of materials. The extremely high intensity and high-energy x-ray beams that are available from third generation synchrotron sources provide unique opportunities for examining materials. We are currently working with faculty from the materials science and civil engineering programs at Georgia Tech to develop methods for the non-destructive evaluation of corrosion in concrete and related systems.