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Superionic Behavior and Phase Transition in a Vanthoffite Mineral

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journal contribution
posted on 11.05.2017, 11:49 by Vaishali Sharma, Diptikanta Swain, Tayur N. Guru Row
Crystals of a Vanthoffite mineral, Na6Mn­(SO4)4, grown from an aqueous solution, belong to a monoclinic system, P21/c, Z = 2, at ambient temperature. Thermal analysis indicates a phase transition at 455 °C, which was substantiated by in situ variable-temperature powder X-ray diffraction. The structure is orthorhombic (Pmmm) after the phase transition and reverts to the monoclinic system upon cooling. Variable-temperature ionic conductivity measurements show a significantly higher value (∼10–2 S cm–1) beyond the phase transition temperature.