Field-assisted sintering technology/Spark plasma sintering is a low voltage, direct current (DC) pulsed current activated, pressure-assisted sintering, and synthesis technique, which has been widely applied for materials processing in the recent years. After a description of its working principles and historical background, mechanical, thermal, electrical effects in FAST/SPS are presented along with the role of atmosphere. A selection of successful materials development including refractory materials, nanocrystalline functional ceramics, graded, and non-equilibrium materials is then discussed. Finally, technological aspects (advanced tool concepts, temperature measurement, finite element simulations) are covered.

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Dense Ca 3 Co 4 O 9 -Na x CoO 2 -Bi 2 Ca 2 Co 2 O 9 (CCO-NCO-BCCO) nanocomposites were produced from sol-gel derived powder by three methods: Spark plasma sintering, hot-pressing and pressureless sintering under O 2 atmosphere. The SPS processed product showed a thermoelectric power factor of 6.6 µW • cm -1 • K -2 at 1073 K in air. A dense nanocomposite with all-scale hierarchical architecture and enhanced thermoelectric properties is only obtained from pressureless sintering under O 2 atmosphere. The resulting nanocomposite enables the simultaneous increase in isothermal electrical conductivity σ and Seebeck coefficient α, and it delivers a thermoelectric power factor of 8.2 µW • cm -1 • K -2 at 1073 K in air. The impact of materials with enhanced electrical conductivity and power factor on the electrical power output of thermoelectric generators was verified in prototypes. A high electrical power output and power density of 22.7 mW and 113.5 mW•cm -2 , respectively, were obtained, when a hot-side temperature of 1073 K and a temperature difference of 251 K were applied. Different p-and n-type materials were used to verify the effect of the thermoelectric figure of merit zT and power factor on the performance of thermoelectric generators.

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