AVS 50th International Symposium
    Electronic Materials and Devices Tuesday Sessions
       Session EM+SC-TuP

Paper EM+SC-TuP13
Electrical, Thermal, and Elastic Properties of MAX Phase Materials

Tuesday, November 4, 2003, 5:30 pm, Room Hall A-C

Session: Poster Session
Presenter: J.D. Hettinger, Rowan University
Authors: S.E. Lofland, Rowan University
P. Finkel, Rowan University
J.D. Hettinger, Rowan University
M.W. Barsoum, Drexel University
A. Ganguly, Drexel University
S. Gupta, Drexel University
K. Harrell, Rowan University
J. Palma, Rowan University
B. Seaman, Rowan University
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We have characterized physical properties of several materials in the MAX phase family.@footnote 1@ These materials derive their name from the basic chemical formula M@sub n@AX@sub n-1@, where M is an early transition metal, A is an A-group element, and X is either N or C. These highly conductive ceramics are readily machinable and possess very desirable structural properties.@footnote 1@ From a systematic study of the transport properties, we find most of these materials require two conduction bands, one consisting of holes and the other of electrons, to explain the electrical conductivity, Hall coefficient, and magnetoresistance. A Wiedemann-Franz analysis of the thermal conductivity suggests that, in most of the materials investigated, the mean-free-path of the entropy carriers is the same as that for the charge carriers. The Lorenz number at room temperature indicates that the thermal conductivity is mostly electronic in nature. We have also performed heat capacity and speed of sound measurements on many of the MAX phase materials allowing the extraction of the elastic moduli and Debye temperatures. We find very good agreement between the Debye temperature as determined from specific heat and that determined from elastic measurements. We find that the electronic term in the specific heat depends strongly on the transition metal element and very weakly on the A-group element. In general we find that the transition metal element impacts the electrical properties more dramatically than the A-group element. In contrast, the A-group element seems to more strongly impact the elastic properties of the materials. The justification for these statements will be presented. This work was supported by the New Jersey Commission on Higher Education, the NSF under grants DMR-0072067 and DMR-0114073 and Rowan University. @FootnoteText@@footnote 1@M. W. Barsoum, Prog. Solid State Chem. 28, 201(2000).