Robert W. Balluffi

Professor Emeritus of Physical Metallurgy

SB Metallurgy, MIT, 1947 
ScD Metallurgy, MIT, 1950

Prof. Balluffi researches the structure and electronic properties of grain boundaries in ZnO. When these boundaries are doped with Bi or Pr and Co or Ni localized electron states are generated at the boundaries. These produce depleted zones and potential barriers at the boundaries leading to material with non-linear I-V properties which is useful for making commercial varistors. The goal of the research is to develop a fundamental understanding of the detailed processes in the boundaries which produce these effects. Bicrystals of pure ZnO containing grain boundaries of controlled geometry are being epitaxially grown on sapphire substrates by a vapor transport technique. Their atomic structures are then being determined by high resolution electron microscopy and computer simulation. These boundaries will then be doped with the above impurities and their structures will be determined as above. In addition, the electronic structures of the boundaries will be calculated, and the relevant electronic properties of the boundaries will be measured. This information should allow the deduction of the source of the varistor behavior.

Selected Publications

Kinetics of Materials, John Wiley and Sons, September 2005 (with Profs. Samuel M. Allen and W. Craig Carter).

"Random Walk Model Model for Self-Diffusivities and Correlation Factors in Periodic Grain Boundaries", Acta Metall. Mater. 42, 1 (1994) (with Q. Ma).

"X-ray Diffraction and Computer Simulation Studies of the Structure of [001] Twist Boundaries in Au-Ag Alloys", Acta Metall. Mater. 42, 3331 (1994) (with I. Majid, C. A. Counterman and P. D. Bristowe).

"Diffusion Induced Grain Boundary Migration and Its Effect on Measuring Chemical Grain Boundary Diffusivities at Low Temperatures". Scripta Metall. Mater. 33, 7 (1995) (with J. Sommer and Y. M. Chiang).