Sintering, high-temperature stability, and thermal conductivity of (Zr, Nb, Hf, Ta)(C, N) high-entropy carbonitrides

Abstract

High-entropy carbonitrides (HECNs), a new class of high-performance ceramics, hold great potential for high-temperature structural materials and thermal protection systems due to their excellent thermal stability and properties. For its better application, it is important to optimize the sintering temperature of HECNs and deeply investigate its thermal conductivity behavior. This study systematically investigates the thermodynamic stability, formation ability, and thermal properties of (ZrHfNbTa)C_xN_1-x through first-principles calculations and experimental validation. Thermodynamic calculations reveal that nitrogen incorporation reduces the sintering temperature required to achieve a stable high-entropy solid solution. Experimental validation by spark plasma sintering (SPS) shows that the sintering temperature can be reduced from 1950 °C to 1700 °C. Ab initio molecular dynamics (AIMD) simulations demonstrate that HECNs retain structural integrity at 1773 K. Thermal conductivity tests show an increase with temperature, but a decrease with higher nitrogen content, which is mainly caused by the increased scattering of phonons resulting from lattice distortions. The Debye-Callaway model fitting further elucidates the underlying thermal conductivity mechanisms. In summary, nitrogen incorporation enhances the thermodynamic stability and reduces thermal conductivity of HECN ceramics, providing valuable theoretical and experimental support for their application in high-temperature structural materials and thermal protection systems.