Cation Defect Mediated Phase Transition in Potassium Tungsten Bronze.
Pei Li1, Renhui Jiang1, Ligong Zhao1
1School of Physics and Technology, Center for Electron Microscopy, MOE Key Laboratory of Artificial Micro- and Nano-structures, and Institute for Advanced Studies, Wuhan University, Wuhan 430072, China.
Inorganic Chemistry
|November 15, 2021
Summary
Heating potassium tungsten bronze (KWO3) reveals phase instability. Cationic defects drive transitions from monoclinic to hexagonal and cubic phases, with an unexpected tetragonal phase forming due to K+ diffusion blockage.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Nanotechnology
Background:
- Potassium tungsten bronze (KWO3) exhibits complex phase behavior under thermal stress.
- Understanding these phase transitions is crucial for high-temperature applications.
Purpose of the Study:
- To investigate the phase instability in KWO3 upon heating.
- To elucidate the atomistic pathway of phase transitions induced by cationic defects.
Main Methods:
- In situ transmission electron microscopy (TEM) was employed to observe phase transformations in real-time.
- Analysis focused on the role of potassium (K) and tungsten (W) vacancies.
Main Results:
- Direct observation of the phase transition pathway: monoclinic K0.20WO3 → hexagonal KWO3 → cubic WO3.
- Identification of cationic defects (K and W vacancies) as key drivers of these transitions.
- Discovery of a K+-rich tetragonal KWO3 phase, potentially due to K+ diffusion blockage at grain boundaries.
Conclusions:
- Cationic defects critically mediate crystal structure changes in KWO3 under heating.
- The findings provide insights for designing KWO3 materials for demanding high-temperature environments.
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