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Solid-gas reactions of complex oxides inside an environmental high-resolution transmission electron microscope
M J Sayagués1, F Krumeich, J L Hutchison
1Instituto de Ciencia de Materiales de Sevilla, C.S.I.C. c/ Américo Vespucio, s/n Isla de la Cartuja, 41092, Sevilla, Spain.
Micron (Oxford, England : 1993)
|February 13, 2001
Summary
This study explores solid-gas reactions in a controlled environment transmission electron microscope (CETEM), revealing novel niobium oxide and niobium tungsten oxide structures. The in situ technique enables atomic-level observation of structural modifications induced by plasma, leading to new synthesis pathways.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Electron Microscopy
Background:
- Conventional solid-state synthesis methods have limitations in producing novel material structures.
- In situ transmission electron microscopy offers atomic-level observation of dynamic processes.
- Plasma-induced reactions can lead to unique structural modifications.
Purpose of the Study:
- To investigate solid-gas reactions of niobium oxides and niobium tungsten oxides under plasma conditions.
- To synthesize novel oxide structures not accessible through conventional methods.
- To elucidate the mechanisms of plasma-induced structural transformations.
Main Methods:
- Utilizing a controlled environment transmission electron microscope (CETEM) with a gas reaction cell (GRC).
- Subjecting non-stoichiometric niobium oxides and niobium tungsten oxides to various gases (O2, H2, He) under plasma.
- Performing in situ atomic-level observation and analysis of reaction products.
Main Results:
- Novel crystal structures of niobium oxides (e.g., Nb(10)O(25)) and niobium tungsten oxides (e.g., (Nb,W)(24)O(64)) were synthesized.
- Detailed three-step oxidation mechanism of monoclinic Nb(12)O(29) was elucidated, involving intermediate phases Nb(11)O(27) and Nb(22)O(54).
- Reversibility of oxidation/reduction reactions and structural destruction by H2 treatment were observed for Nb(12)O(29).
- Niobium tungsten oxides decomposed into WO(3-x) and a novel TTB-type superstructure (Nb,W)(24)O(64).
- Disordered bronze-type structures with segregated WO(3) domains formed from specific niobium tungsten oxides under oxygen plasma.
Conclusions:
- In situ plasma-assisted reactions in CETEM provide a powerful route for synthesizing novel oxide materials.
- The study reveals new insights into the reaction mechanisms and structural transformations of niobium-based oxides.
- This technique opens avenues for exploring and creating complex inorganic materials.