Effect of carbothermal reduction on microstructure, oxygen concentration, and thermal conductivity of Si <sub>3</sub> N <sub>4</sub> ceramics
Binbin Fan, Tianci Wang, Bohan Wang, Dengke Zhao, Shuo Zhao, Shijia Zhang, Fei Li, Zunlan Hu, Zhipeng Xie, Kexin Chen, Guanghua Liu
Abstract
Abstract This study elucidates the role of carbothermal reduction in tailoring the microstructure, oxygen concentration, and thermal conductivity of Si₃N₄ ceramics synthesized via two‐step gas pressure sintering. Carbon incorporation promoted the evolution of elongated β‐Si₃N₄ grains and altered the nature of intergranular phases. Electron energy loss spectroscopy (EELS) revealed substantial lattice oxygen depletion in C‐doped specimens, alongside a pronounced diffusion gradient from grain interiors to boundaries in undoped samples—indicative of oxygen redistribution driven by concentration gradients. These modifications, combined with thinner grain boundary films and a reduced volume fraction of secondary phases, substantially boosted heat conduction. As a result, the thermal conductivity of the C‐doped ceramic reached 97 W·m⁻¹·K⁻¹, representing a 54% enhancement over its undoped counterpart. This work underscores the efficacy of carbothermal reduction as a microstructural and chemical engineering approach to advance the thermal performance of Si₃N₄ ceramics for next‐generation thermal management technologies.