The focus of my research is a systematic study of grain boundaries and interfaces relating their geometry, structure, chemistry, and energetics with their electrical properties.

Grain boundaries, despite their importance in technological materials, are among the least understood areas in materials science because of their complexity. There are working devices, for example: high temperature superconducting quantum interference devices (squids) likely to be used in the first magnetic cardiograms, zinc oxide varistors in surge protectors, and positive temperature coefficient (PTC) materials in temperature activated switches. They all use novel electrical transport properties of grain boundaries. Since five geometric parameters are generally needed to specify a boundary, not all grain boundaries are alike even in the same materials. Therefore, contradicting results involving electrical measurements on boundaries are not uncommon in the literature. A significant part of our research is to identify boundary types that have similar electrical responses to facilitate the usage of boundaries in devices.

In addition to isolating a particular boundary to observe its structure by high resolution electron microscopy, and relate that to its electrical properties measured, we are also examining an assembly of boundaries and the combined effects on percolation paths and electrical transport. Computational methods in predicting the types of boundaries remained and the general orientation texture after grain growth are being developed.

In an overall theme, our research is aimed at searching for the basic understanding of boundaries and interfaces and applying the knowledge for better engineered electrical properties of materials for applications and new devices.