Ordered and twinned structure in hexagonal-based potassium tungsten bronze nanosheets

Non-stoichiometric hexagonal-based potassium tungsten bronze (K_xWO₃) nanosheets were synthesized by oxidizing tungsten foil in potassium hydroxide. The tungsten bronze nanosheets exhibited an ordered monoclinic superstructure as revealed by X-ray diffraction patterns. Further detailed structural investigation by employing electron microscopy techniques showed the coexistence of 120° rotation twinning variants in the superstructure phase, which may result from the rotation symmetry reduction induced by the ordered arrangements of K vacancies during crystal growth.