Thermal design for enhanced temperature uniformity on spark plasma sintering device

Spark plasma sintering (SPS) is a widely used technique for sintering thermoelectric devices. In this process, the heat generated by Joule heating is primarily transferred to the die surface through radiative heat transfer, causing temperature non-uniformity within the specimen. These discrepancies in temperature distribution cause localized changes in the properties of the thermoelectric device, which presents significant engineering challenges in managing heat transfer during the sintering process. This study proposes a thermal design approach to reduce the temperature gradient within the specimen in the existing SPS device. The idea of the auxiliary heating system was evaluated using numerical simulation validated with experimental comparison. Design variables, heating power (an operating parameter) and heater depth (a geometric parameter), were chosen to balance the amount of Joule heating to the heat produced by the auxiliary heating system. The optimization process with sensitivity analysis led to the selection of an auxiliary heating system capable of reducing the temperature gradient within 61.1 K/m. This achievement allows for the sintering of thermoelectric devices with enhanced thermoelectric performance.