Acoustic shock-wave induced structural phase transition (ordered-to-disordered) associated dielectric transition (space charge-to-dipolar polarization): A case study of structure–property relationship in lithium sulfate monohydrate single crystal

Abstract

The purpose of this study is to investigate the structure–property correlations of Li2SO4 · H2O to better understand the function of the disordered phase with respect to its dielectric and thermal properties. The lattice Raman spectral results show that the order of the molecular units during the ordered-to-disordered phase transition is primarily contributed by H2O > SO4 > Li2+. This indicates that the rearrangement of the H2O and SO4 molecular units is primarily responsible for the change in functional properties. In contrast to the ordered phase, the disordered phase exhibits abnormal dielectric behavior, as evidenced by the impedance spectral data, which indicate increased electrical conductivity and a larger dielectric constant at higher frequencies, primarily due to the rearrangement of H2O units and the rotational disorder of SO4 units. The title compound's dehydration and decomposition processes provide compelling evidence that it is possible to understand the ordered–disordered phase transition, which causes dehydration to take longer in the disordered state. On account of the uneven thermal decomposition process, the endothermic peak, which represents the β–α Li2SO4 conversion, exhibits peak splitting at ∼575 °C. The observed anomalous dielectric behavior (e.g., higher dielectric constant at higher frequency, @ 1 MHz) is likely for the first time to date, based on the current findings and the 80 years of literature already available on the title crystal. The disordered phase of Li2SO4 · H2O may be an excellent fit for electrolyte applications in solid-state batteries because of its remarkable dielectric characteristics.