Thermal Expansion, Microstructure and Mechanical Properties of Rapid Microwave Sintering Mn3Cu0.5Ge0.5N0.9C0.1 in Nitrogen Atmosphere

Microwave sintering enabled the efficient fabrication of bulk Mn3Cu0.5Ge0.5N0.9C0.1 NTE materials in 3–5 h, versus 2 to 8 days for conventional methods. The microwave approach demonstrated high efficiency and energy savings. By adjusting temperature and dwell time, the NTE operating range can be shifted to lower temperatures. Under the optimized condition of 800 °C for 4 h, the resulting bulk material achieved an NTE coefficient of −20.56 × 10−6 K−1 over a temperature interval ΔT of 88 K (from 159 K to 247 K), along with favorable densification and high hardness. The demonstrated processing efficiency, microstructural control, and tunable NTE properties establish a solid foundation for potential industrial scale-up.