Obtaining a copper selenide base material by powder metallurgy methods

Copper selenide is a promising material for power generation in medium−temperature range 600—1000 K. A number of features of the Cu—Se system, i.e. the existence of a phase transition in Cu2Se compound, the high speed of Cu ion diffusion and the high vapor pressure of Se at high temperatures, necessitate massive experimental investigations aimed to develop and optimize a method for obtaining a copper selenide base bulk material. In this work the effect of mechanochemical synthesis mode and subsequent compaction method on the thermoelectric properties and structure of copper selenide were studied. The source material was obtained by mechanochemical synthesis. The hot pressing and spark plasma sintering methods were used for obtaining the bulk samples. The structure and phase composition were studied by X−ray diffraction and scanning electron microscopy. We show that increasing the time of mechanochemical synthesis to 5 hours leads to copper depletion of the powders and the formation of nonstoichiometric phase Cu1,83Se which persists after spark plasma sintering. Comparison of the structure and properties of the material obtained by spark plasma sintering and hot pressing showed that the material obtained by hot pressing has a greater degree of the grain defects. The highest thermoelectric efficiency ZT = 1.8 at 600 °C was observed in the material obtained by spark plasma sintering. We show that the main factor affecting the value of the thermoelectric efficiency ZT of the studied materials is the low thermal conductivity. The difference in thethermal conductivities of the materials obtained by different methods is attributed to the electronic component of thermal conductivity.

thermoelectric material, copper selenide, mechanochemical synthesis, spark plasma sintering, hot pressing, nanocomposite materials, thermoelectric properties

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