Field-Assisted Sintering Technology (FAST) or Spark Plasma Sintering (SPS) is a low-voltage, direct current (DC) pulsed current-activated, pressure-assisted sintering and synthesis technique. This method has been widely applied in materials processing due to its ability to synthesize new compounds and densify materials in one step. The process involves a mechanical loading system that acts as a high-power electrical circuit, placed in a controlled atmosphere. Low voltages (typically below 10 V) produce high currents (1-10 kA), leading to efficient Joule heating. The heating rates can be as high as 1000 °C/min, and cooling rates up to 150 °C/min are possible. The simultaneous application of uniaxial mechanical pressure enhances densification, and the process can be conducted under vacuum or protective gas at atmospheric pressure. The working principle of FAST/SPS involves mechanical, thermal, and electrical effects. Mechanical effects include the quasi-static compressive stress applied, which improves particle contact and enhances densification mechanisms. Thermal effects are significant due to the high heating rates, which can enhance densification while retarding microstructure coarsening. Electrical effects, such as percolation, Peltier effect, and electrochemical reactions, play a role in the microstructure formation. The role of the atmosphere is also crucial. The composition and partial pressure of the sintering atmosphere influence defect structure, diffusivity, and phase stability. Reducing atmospheres can enhance surface diffusion and reduce grain growth, while inert gases can prevent reactions with the sample. Materials developed using FAST/SPS include refractory metals, intermetallics, ultra-high-temperature ceramics (UHTC), transparent ceramics, and nanostructured materials. Refractory metals like tungsten and tantalum benefit from the high heating rates and short dwell times, leading to better control of the final microstructure. UHTC materials, such as borides, carbides, and nitrides, are challenging to sinter due to their high covalent bonding and low self-diffusion coefficients, but FAST/SPS allows for controlled densification and improved microstructure. Transparent ceramics, like yttrium-aluminum-garnet (YAG), benefit from the one-step process and short cycle times. Nanostructured materials, such as zirconia and titania, can achieve average crystallite sizes below 50 nm, enhancing their mechanical and functional properties. Overall, FAST/SPS offers significant advantages in terms of material processing, including improved densification rates, reduced grain growth, and enhanced microstructure control, making it a valuable technique for a wide range of materials and applications.Field-Assisted Sintering Technology (FAST) or Spark Plasma Sintering (SPS) is a low-voltage, direct current (DC) pulsed current-activated, pressure-assisted sintering and synthesis technique. This method has been widely applied in materials processing due to its ability to synthesize new compounds and densify materials in one step. The process involves a mechanical loading system that acts as a high-power electrical circuit, placed in a controlled atmosphere. Low voltages (typically below 10 V) produce high currents (1-10 kA), leading to efficient Joule heating. The heating rates can be as high as 1000 °C/min, and cooling rates up to 150 °C/min are possible. The simultaneous application of uniaxial mechanical pressure enhances densification, and the process can be conducted under vacuum or protective gas at atmospheric pressure. The working principle of FAST/SPS involves mechanical, thermal, and electrical effects. Mechanical effects include the quasi-static compressive stress applied, which improves particle contact and enhances densification mechanisms. Thermal effects are significant due to the high heating rates, which can enhance densification while retarding microstructure coarsening. Electrical effects, such as percolation, Peltier effect, and electrochemical reactions, play a role in the microstructure formation. The role of the atmosphere is also crucial. The composition and partial pressure of the sintering atmosphere influence defect structure, diffusivity, and phase stability. Reducing atmospheres can enhance surface diffusion and reduce grain growth, while inert gases can prevent reactions with the sample. Materials developed using FAST/SPS include refractory metals, intermetallics, ultra-high-temperature ceramics (UHTC), transparent ceramics, and nanostructured materials. Refractory metals like tungsten and tantalum benefit from the high heating rates and short dwell times, leading to better control of the final microstructure. UHTC materials, such as borides, carbides, and nitrides, are challenging to sinter due to their high covalent bonding and low self-diffusion coefficients, but FAST/SPS allows for controlled densification and improved microstructure. Transparent ceramics, like yttrium-aluminum-garnet (YAG), benefit from the one-step process and short cycle times. Nanostructured materials, such as zirconia and titania, can achieve average crystallite sizes below 50 nm, enhancing their mechanical and functional properties. Overall, FAST/SPS offers significant advantages in terms of material processing, including improved densification rates, reduced grain growth, and enhanced microstructure control, making it a valuable technique for a wide range of materials and applications.