Thermal and electrical properties of single‐phase high entropy carbide ceramics

Abstract Thermal and electrical properties were investigated for five nominally phase‐pure high entropy carbide ceramics. The compositions (Hf 0.2 Nb 0.2 Ta 0.2 Ti 0.2 Zr 0.2 )C, (Cr 0.2 Hf 0.2 Ta 0.2 Ti 0.2 Zr 0.2 )C, (Hf 0.2 Mo 0.2 Ta 0.2 Ti 0.2 Zr 0.2 )C, (Hf 0.2 Ta 0.2 Ti 0.2 W 0.2 Zr 0.2 )C, and (Hf 0.2 Mo 0.2 Ti 0.2 W 0.2 Zr 0.2 )C were synthesized by carbothermal reduction of oxides. The thermal diffusivity and heat capacity were measured from room temperature to 1800°C. The room temperature thermal conductivity ranged from 5.1 W/mK for (Hf 0.2 Mo 0.2 Ti 0.2 W 0.2 Zr 0.2 )C to 9.0 W/mK for (Cr 0.2 Hf 0.2 Ta 0.2 Ti 0.2 Zr 0.2 )C. The thermal conductivity increased over the temperature range with maximum conductivities of 19.6 W/mK measured for (Hf 0.2 Mo 0.2 Ta 0.2 Ti 0.2 Zr 0.2 )C to 29.7 W/mK for (Cr 0.2 Hf 0.2 Ta 0.2 Ti 0.2 Zr 0.2 )C at 1800°C. The electron contribution to thermal conductivity calculated from measured electrical resistivity varied from 41% to 52% of the total thermal conductivity. The tungsten and molybdenum containing compositions had higher phonon contributions while the niobium and chromium containing compositions had nearly equal electron and phonon contributions to thermal conductivity.