Abstract
High-resolution electron microscopy reveals the microdomain structure of Ag-ion-exchanged LiTaO3. At least three distinct pervoskite-related structures (Li1-xAgxTaO3; 0 ≤ x ≤ 1) (space groups Pnma, Im3 and R3c) coexist with each other, or with LiTaO3 and AgTaO3, depending on the duration of ion-exchange in molten AgNO3. The images also reveal that the exchange takes place via medium of chemically-induced microtwinning, whereby the Ag atoms may replace Li and occupy sites of larger coordination polyhedra at the twin planes. This mechanism is preferred kinetically over a strictly regimented, coherent, topotactic dilatory-type transformation.

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