A novel electrical testing assembly was designed, fabricated, and validated to allow elevated temperature electrical resistivity measurements using the van der Pauw method up to 2173 K. The assembly consisted of h-BN insulators, ZrB2-based fixture components, and W signal wires. The assembly was installed in a refractory metal element furnace for temperature control and an oxygen gettering system was utilized to control the oxygen activity of the process gas. The system was validated using high-purity Mo as a reference standard, demonstrating good agreement with accepted electrical resistivity values for Mo. The system was utilized to measure the electrical resistivity of a ZrB2 ceramic that was produced from commercially available ZrB2 powder using C and ZrH2 as sintering aids and densified by hot-pressing at 2423 K. The resulting ZrB2 ceramic was ~96% dense with ~0.2 wt.% ZrO2 secondary phase and a grain size of ~40 µm. Electrical resistivity of ZrB2 was measured from room temperature to 2133 K. The electrical resistivity of the ZrB2 exhibited distinct linear behavior with respect to temperature, increasing from 7.3 µΩ-cm at 298 K to 35.7 µΩ-cm at 1223 K (~0.031 µΩ-cm/K), and then further increasing to 76.0 µΩ-cm at 2133 K (~0.044 µΩ-cm/K). To the knowledge of the authors, these measurements were performed at the highest temperatures ever reported using this method.
- Electrical Resistivity,
- UHTC,
- Zirconium Diboride
Available at: http://works.bepress.com/greg-hilmas/242/