Influence of DC and AC current in the SPS sintering process on homogeneity of thermoelectric properties of Cu2S and Cu2Se

Cu2Se and Cu2S belong in recent years to the most intensively studied thermoelectric materials, due to a very high values of the thermoelectric figure of merit ZT parameter. The main reason limiting their applicability is their degradation under the influence of flowing electrical current. The most commonly used sintering technique in the case of thermoelectric materials is the spark plasma sintering SPS method, which uses a DC current and is also used in the sintering process in many other groups of ceramic, semiconductor and nanocrystalline materials. In this work, Cu2S and Cu2Se powders were sintered using the constructed SPS apparatus equipped with two independent power sources, i.e., with direct current (DC) and alternating current (AC). The paper shows that the degradation of superionic thermoelectric materials can, unfortunately, occur during the sintering process as a result of the DC current flow. At the same time, the use of AC current allows the preservation of all the ad-vantages of the SPS technique, such as, e.g. high speed of the process, but additionally shows that the migration of ions does not appear and thus the use of AC current seems to be more appropriate approach in the case of sintering various superionic materials.