High-Pressure Spectroscopic Study of Hydrous and Anhydrous Cs-Exchanged Natrolites

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• 作者：Dan Liu ; Donghoon Seoung ; Yongmoon Lee ; Zhenxian Liu ; Jong-Won Lee ; Ji-Ho Yoon ; Yongjae Lee
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：January 26, 2012
• 年：2012
• 卷：116
• 期：3
• 页码：2159-2164
• 全文大小：1009K
• 年卷期：v.116,no.3(January 26, 2012)
• ISSN：1932-7455

文摘

Structural phase transitions in hydrous Cs-exchanged natrolite (Cs-NAT-hyd) and anhydrous Cs-exchanged natrolite (Cs-NAT-anh) have been investigated as a function of pressure and temperature using micro-Raman scattering and synchrotron infrared (IR) spectroscopy with pure water as the penetrating pressure medium. The spectroscopic results indicate that Cs-NAT-hyd undergoes a reversible phase transition around 4.72 GPa accompanied by the discontinuous frequency shifts of the breathing vibrational modes of the four-ring and helical eight-ring units of the natrolite framework. On the other hand, we observe that Cs-NAT-anh becomes rehydrated at 0.76 GPa after heating to 100 掳C and then transforms into two distinctive phases at 2.24 and 3.41 GPa after temperature treatments at 165 and 180 掳C, respectively. Both of these high-pressure phases are characterized by the absence of the helical eight-ring breathing modes, which suggests the collapse of the natrolite channel and formation of dense high-pressure polymorphs. Together with the fact that these high-pressure phases are recoverable to ambient conditions, our results imply a novel means for radionuclide storage utilizing pressure and a porous material.