DEINTERCALATION OF AN ALKALI METAL FROM A 2D KAGOMÉ METAL
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Date
2021-08-11
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Johns Hopkins University
Abstract
Kagomé metals are a recently discovered class of quantum material that have the potential to underlie more efficient and novel computing devices, if appropriately tunable and harnessable. A prototypical kagomé metal, the structure of KV3Sb5 was previously discovered to be in the P6/mmm space group and to display a kagomé net of vanadium atoms with potassium ions intercalated between slabs of V-Sb. KV3Sb5 shows potential for accessible Fermi Energy (EF) tuning due to possible ease of deintercalation of potassium from the compound. Previous work has demonstrated uncontrolled deintercalation by etching in hot HNO3 as well as treatment with water. In this work, controlled deintercalation of potassium via [I2 + I-] in acetonitrile (ACN) was explored. Using the change in lattice parameter ratios (c/a) as a proxy, the effect of initial electrochemical potential of the ACN solution on potassium occupancy is demonstrated. The occupancy was shown to depend on the initial electrochemical potential of the solution, but with other contributing factors. Further, it was observed that the electrochemical potential of the solution did have an effect on structural decomposition of KV3Sb5. The extent of decomposition was explored and was found have a linear dependence on initial electrochemical potential of the ACN solution used for deintercalation. AC susceptibility measurements of samples post-deintercalation show a change in behavior at ≈ 2K with a decrease in potassium occupancy and degree of decomposition. These results demonstrate the difficulty of precisely controlling alkali metal content while avoiding secondary products during the synthesis of kinetically stable phases, and provide guidance of the challenges that must be overcome to make controllable chemical tuning of kagomé metals, a prerequisite for their use in functional devices, a reality.
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Kagomé metal