Thermal «memory effect» in quintinite polytypes-2H, -3R and-lM
Panikorovskii T. L., Zhitova E. S., Krivovichev S. V., Zolotarev A. A., jr., Britvin S. N., Yakovenchuk V. N., Krzhizhanovskaya M. G.
Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2015. V. 144. N 2. P. 109-119
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Language: Russian
Abstract
Thermal behavior and character of a «memory effect» in 2H, 3R and 1M polytypes of quintinite from phoscorites of the Kovdor massif (Kola Peninsula, Russia) have been studied by methods of the high temperature X-ray powder diffraction, single crystal X-ray diffraction, infrared spectroscopy and differential scanning calorimetry. There have been revealed several consequent stages in the quintinite transformation under furnacing: dehydration from molecular water and the «collapsing» of metal-hydroxide layers at the heating up to 200 °C; formation of the 1H polytype at 250 °C; transition of the 1H polytype into the phase with a periclase structure at 375 °C. In so doing, after dehydration and formation of 1H polytype, the crystal structures of 2H and/or 1M (3R) polytypes of quintinite becomes completely self-restored under atmospheric conditions. This «memory effect» in quintinite-2H, -3R and -1M is provided by dependence of the inter-layer space in its structure on the structural organization of cations inside hydroxide layers.
Key words: quintinite-2H, quintinite-1M, quintinite-3R, «memory effect», natural layered double hydroxides, phase transitions, 1H polytype.
