Thermal and Electrical Transport Properties of Spark Plasma-Sintered HfB2 and ZrB2 Ceramics

The thermal and electrical transport properties of various spark plasma-sintered HfB2- and ZrB2-based polycrystalline ceramics were investigated experimentally over the 298-700 K temperature range. Measurements of thermal diffusivity, electrical resistivity, and Hall coefficient are reported, as well as the derived properties of thermal conductivity, charge carrier density, and charge carrier mobility. Hall coefficients were negative confirming electrons as the dominant charge carrier, with carrier densities and mobilities in the 3-5 x 10(21) cm(-3) and 100-250 cm(2). (V. s)(-1) ranges, respectively. Electrical resistivities were lower, and temperature coefficients of resistivity higher, than those typically reported for HfB2 and ZrB2 materials manufactured by the conventional hot pressing. A Wiedemann-Franz analysis confirms the dominance of electronic contributions to heat transport. The thermal conductivity was found to decrease with increasing temperature for all materials. Results are discussed in terms of sample morphology and compared with data previously reported in the scientific literature.