Field-assisted sintering technology (FAST)/Spark plasma sintering (SPS) is a low-voltage, direct current (DC) pulsed current-activated, pressure-assisted sintering and synthesis technique widely used for materials processing. It combines mechanical pressure with electrical effects to densify materials and synthesize compounds. The process involves a mechanical loading system and a high-power electrical circuit in a controlled atmosphere, enabling efficient Joule heating and rapid densification. The electrical conductivity of the sample and tool determines the current flow and heating patterns. Conductive samples allow direct current flow through the material, while non-conductive samples rely on Joule heating via conductive tools. The process can be applied under vacuum or protective gas, with high heating rates up to 1000°C/min and cooling rates up to 400°C/min. Mechanical pressure enhances densification, with maximal loads up to 250 kN. The process is controlled by temperature measurement, with the ability to achieve temperatures up to 2400°C using standard graphite tools. Mechanical effects in FAST/SPS improve particle contact, enhance existing densification mechanisms, and activate new ones like plastic deformation. Thermal effects include high heating rates, which can enhance densification while retarding microstructure coarsening. Electrical effects involve current flow through the sample, leading to percolation effects, Peltier heating, and electrochemical reactions. These effects influence microstructure formation, with current paths creating localized heating and densification. Atmosphere plays a crucial role in controlling defect structure, diffusivity, and phase stability. Reducing atmospheres can enhance surface diffusion and reduce oxide formation, while vacuum minimizes contamination. Materials developed using FAST/SPS include refractory metals like tungsten and its alloys, intermetallics such as NiAl and FeAl, ultra-high-temperature ceramics (UHTCs) like ZrB₂ and HfB₂, and transparent ceramics like YAG and ZrO₂. Nanostructured materials are also produced, with grain sizes below 50 nm, offering improved mechanical and functional properties. FAST/SPS enables better control of microstructure and densification, with applications in aerospace, energy, and optoelectronics. Challenges remain in achieving full densification and minimizing grain growth, particularly for materials with high oxygen contamination. The technique is increasingly used for its efficiency, scalability, and ability to produce high-performance materials with tailored properties.Field-assisted sintering technology (FAST)/Spark plasma sintering (SPS) is a low-voltage, direct current (DC) pulsed current-activated, pressure-assisted sintering and synthesis technique widely used for materials processing. It combines mechanical pressure with electrical effects to densify materials and synthesize compounds. The process involves a mechanical loading system and a high-power electrical circuit in a controlled atmosphere, enabling efficient Joule heating and rapid densification. The electrical conductivity of the sample and tool determines the current flow and heating patterns. Conductive samples allow direct current flow through the material, while non-conductive samples rely on Joule heating via conductive tools. The process can be applied under vacuum or protective gas, with high heating rates up to 1000°C/min and cooling rates up to 400°C/min. Mechanical pressure enhances densification, with maximal loads up to 250 kN. The process is controlled by temperature measurement, with the ability to achieve temperatures up to 2400°C using standard graphite tools. Mechanical effects in FAST/SPS improve particle contact, enhance existing densification mechanisms, and activate new ones like plastic deformation. Thermal effects include high heating rates, which can enhance densification while retarding microstructure coarsening. Electrical effects involve current flow through the sample, leading to percolation effects, Peltier heating, and electrochemical reactions. These effects influence microstructure formation, with current paths creating localized heating and densification. Atmosphere plays a crucial role in controlling defect structure, diffusivity, and phase stability. Reducing atmospheres can enhance surface diffusion and reduce oxide formation, while vacuum minimizes contamination. Materials developed using FAST/SPS include refractory metals like tungsten and its alloys, intermetallics such as NiAl and FeAl, ultra-high-temperature ceramics (UHTCs) like ZrB₂ and HfB₂, and transparent ceramics like YAG and ZrO₂. Nanostructured materials are also produced, with grain sizes below 50 nm, offering improved mechanical and functional properties. FAST/SPS enables better control of microstructure and densification, with applications in aerospace, energy, and optoelectronics. Challenges remain in achieving full densification and minimizing grain growth, particularly for materials with high oxygen contamination. The technique is increasingly used for its efficiency, scalability, and ability to produce high-performance materials with tailored properties.