Hydration behavior of Na-smectite crystals synthesized at high pressure and high temperature

Abstract--Hydration behavior of Na-smectite crystals ynthesized ata pressure of 5.5 GPa and temper-atures of 1400"-1500 ~ was examined by X-ray powder diffraction at various relative humidities (RH) in the range of 0-100%. The basal spacing of the Na-smectite crystal increased stepwise with increase in RH. The reflections observed were only normal reflections of a single or dual hydration states of smectite. No irrational, intermediate, or asymmetrical reflections were observed. The simple hydration behavior, not known for natural smectite with fine particle sizes and low crystallinity, indicates that he Na-smectite crystals are as perfect as common inorganic rystals with an ordered structure. Key Words--High-pressure experiment, Hydration, Relative humidity, Smectite crystal