A Spark Plasma Sintering (SPS) Furnace, also known as Field Assisted Sintering Technique (FAST), is a high-speed consolidation technology that uses a combination of uniaxial pressure and high-intensity, low-voltage pulsed direct current (DC) to densify materials.

For battery R&D, SPS is a critical "mechanical necessity." It allows you to achieve near-theoretical density in minutes, whereas conventional muffle furnaces require hours. This speed is vital for suppressing the evaporation of volatile elements like Sodium and Lithium.

Unlike conventional sintering which relies on external radiant heat, SPS utilizes internal Joule heating. (1) Joule Heating: The pulsed current passes directly through the conductive graphite die and, if the sample is conductive, through the sample itself. This creates rapid heating rates (up to 600℃/min). (2) Plasma Effect (Debated): Historically, it was believed that "sparks" or "plasma" were generated between powder particles, stripping away surface oxides. While recent 2026 studies (e.g., from Tohoku University) suggest the densification is primarily driven by pressure and rapid heat, the term "SPS" remains the industry standard. (3) Uniaxial Pressure: High pressure (10–100 MPa) is applied during heating, which physically collapses pores and promotes plastic deformation at lower temperatures than pressureless sintering.  

References:

J. Wu, et al., Microwave sintering and in-situ transmission electron microscopy heating study of Li1·2(Mn0·53Co0.27)O2 with improved electrochemical performance, Journal of Power Sources, 2016, 326, 104-111.

X. Wang, et al., Low temperature and rapid microwave sintering of Na3Zr2Si2PO12 solid electrolytes for Na-Ion batteries, Journal of Power Sources, 2021, 481, 228924

K. I. Rybakov, et al., Microwave Sintering: Fundamentals and Modeling, J. Am. Ceramic Soc., 2013, 96, 1003-1020.