Bernhardt J. Wuensch

Professor of Ceramics

SB Physics, MIT 1955
SM Physics, MIT, 1957
PhD Crystallography, MIT, 1963

Room 13-4037, 77 Mass. Ave., Cambridge, MA  02139
617-253-6889 (phone) 617-253-5827 (fax)
wuensch@mit.edu

Prof. Wuensch's group is performing research on single crystal or powder samples using neutron or X-ray diffraction to obtain precise values for atomic coordinates in crystals, site occupancy factors, and parameters that characterize both harmonic and anharmonic components of thermal vibration. Ordering and superstructure formation, partitioning of ions among sites in solid solutions, structural changes during phase transformations, and the thermal motion and diffusion paths of mobile ions in fast-ion conductors are examples of the sorts of problems on which they are working. Other research concerns point defects in oxides and diffusion along grain boundaries or as a function of direction in single crystals. Both stable and radioactive isotopes are employed as tracers. Their distribution is established with probes such as secondary ion mass spectrometry or electron microprobe analysis. It is necessary in most of the group's work to synthesize unique powders or single-crystals that are suitable for study. Crystal growth is frequently the main focus of a problem and a variety of methods are utilized: growth from solution or melts, chemical vapor transport, and high-pressure hydrothermal reaction. 

Selected Publications

Fast-Ion Conducting Y₂ (Zr_y Ti_1-y)₂O₇ Pyrochlores: Neutron Rietveld Analysis of Disorder Induced by Zr Substitution", J. Solid State Chem. 117 (1): 108-121 (1995) (with others). 

"Toward Determination of Reliable Grain Boundary Diffusion Coefficients for Oxides," Ceramic Trans. 71: 101-116 (1996) (with others). 

"Structure of Na₃NdSi₆O₁₅ ·2H₂O--A Layered Silicate with Paths for Possible Fast-Ion Conduction," Acta Crystallogr.B53 (1): 7-17 (1997) (with others). 

Teaching Involvements

Fall 2006 3.035-3.04 Special Problems in Materials Science
Fall 2006 3.60 Symmetry, Structure, and Tensor Properties
Fall 2006 3.072 Symmetry, Structure, and Tensor Properties: Mils. Lec
Spring 2007 3.035-3.04 Special Problems in Materials Science
Spring 2007 3.073 Diffraction and Structure
Spring 2007 3.271 Diffraction and Structure