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Updated: Dec 20, 2025

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
Minerals to Functional Materials: Characterization of Structural Phase Transitions and Raman Analysis of a Superionic
Ajana Dutta1, Diptikanta Swain1, Janaky Sunil2
1Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, Karnataka, India.
Abstract:
In search of promising Na+ ion conductors, we have detected a superionic phase in a Vantoffite mineral, Na6Co(SO4)4, at 570 °C, thus enhancing the use of minerals to produce futuristic solid state electrolytes. Na6Co(SO4)4 crystallizes concomitantly to produce di- and tetrahydrate forms from an aqueous solution. Both the crystal forms belong to a triclinic system, space group P1. The mineral transforms to a dehydrated phase as established by in situ single crystal X-ray diffraction at 217 °C and is shown to be isostructural with its Mn analogue. Even though thermal analysis indicates a single structural phase transition at 450 °C, the features associated with in situ powder X-ray diffraction as well as in situ Raman spectroscopy signify a second phase transition ≈540 °C and the behavior of ionic conductivity leads to a superionic phase (σ ≈ 10-2 S/cm at 570 °C). These observations are significant for the development and understanding of mineral based solid electrolytes.
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