APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022;
Chicago
Session T00: Poster Session III (1pm- 4pm CST)
1:00 PM,
Thursday, March 17, 2022
Room: McCormick Place Exhibit Hall F1
Abstract: T00.00354 : Solid electrolyte behaviour in K3H(SeO4)2 studied by defect interaction.
Abstract
Presenter:
Oscar S Hernandez-Daguer
(Mount Holyoke College)
Author:
Oscar S Hernandez-Daguer
(Mount Holyoke College)
Collaborations:
O.S. Hernandez-Daguer, D. Peña-Lara
This paper explores and proposes a structure-conductivity correlation in the K3H(SeO4)2 (TKHSe) crystal. The thermal transformation which appears around Tp = 388 K is endothermic in addition to showing a slight weight loss. The enthalpy (ΔH) and weight loss changes on successive heating and cooling runs through Tp slightly decrease, showing that Tp marks the onset of a slow thermal dehydration of TKHSe. The step change in the dc- ionic conductivity of three orders of magnitude is also reduced slightly on successive heating and cooling runs. Our results then show that the observed ΔH at Tp is due to a first-order phase transition of the order-disorder type with that occurs simultaneously with a slow dehydration process. Moreover, the observed decrease of the magnitude of conductivity on successive thermal runs is a consequence of decomposition at the surface of the TKHSe grains, but the jump in conductivity is only a consequence of the order-disorder transition in the TKHSe phase that remains inside the grains. The observed first-order phase transition that leads to the fast-ion conducting phase in TKHSe above Tp is studied by a trial free energy density. By properly adjusting the model parameters, an abrupt change of disordering mobile ion concentration, c'(T), is predicted at a transition temperature, Tp. The temperature dependence of the dc-conductivity, σ, is well fitted to the c´(T) equilibrium configuration obtained from the trial free energy function. Using a trial free energy density model was possible to fit the Phase II and the jump in conductivity curves for K3H(SeO4)2. This fact shows the conductivity phenomena in this compound is due to solid-solid phase transition. And why the most known models, just can't explain, based on the crystal structure satisfactorily the high proton conductivity phase. Whereby we propose; more than one mechanism or interaction is required to fully explain the conductivity phenomena in phase I and II in the K3H(SeO4)2.