Berlin 2024 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 32: Crystal Structure Defects / Real Structure / Microstructure II

KFM 32.2: Vortrag

Freitag, 22. März 2024, 09:50–10:10, E 124

Hidden structural transition upon dehydration of Prussian Blue analogues (PBAs) — •Yevheniia Kholina and Arkadiy Simonov — ETH Zurich, Switzerland, Department of Materials, Laboratory for Disordered Materials

Prussian blue analogues (PBAs) are a diverse family of transition metal cyanide materials with chemical formula M[M’(CN)₆]_1−x·_y·nH₂O, which we abbreviate here as M[M’] (M and M’=transition metal ions, =vacancy). These materials are known for their highly connected porous network, enabled by structural vacancies of M’(CN)₆ with sufficiently large channels to transport or store small molecules and ions. Currently, these systems are actively investigated for application as hydrogen storage media, humidity sensors, and alkali ion sieves. One step that is often overlooked in the research is drying. PBAs are typically grown from water solutions and water has to be removed by heating the sample either in a vacuum or in a dry atmosphere. Since drying doesn’t change the average structure, it is generally assumed that this step doesn’t alter the porous network of PBAs. We demonstrate that the dehydration step in fact causes a hidden structural transition that involves irreversible rearrangements of vacancies. Such rearrangements modify the pore-network characteristic, like the fraction of accessible volume and conductance of matter through the channels. We collect diffuse scattering from Mn[Co] single crystals and use 3D-ΔPDF analysis to characterize their local structure and monitor structural changes upon water removal.