The Electron Microscopy Investigations Of Electron-beam-induced Growth And Reduction Of WO_2.72 Single Crystal

Tungsten oxide nano-materials have excellent properties and abundant structures.In addition to the common integer stoichiometric states,there are large numbers of non-stoichiometric structures of tungsten oxide.WO_2.72 is the only one with advantages of both structural stability and maximum surface oxygen vacancies,so it is widely used.The increase of material conductivity caused by the increase of oxygen vacancies is the key to improve the performance,but most studies can't observe the process of material deoxidization and reduction directly at present.The preparation of non-stoichiometric tungsten oxide with high crystallinity has always been a research hotspot.The existing preparation methods of WO_2.72 are time-consuming and require too much.Due to its sensitivity and convenience,electron beams have been used to obtain highly crystalline non-stoichiometric tungsten oxide successfully.Aid by transmission electron microscope,the growth and reduction processes of WO_2.72 single crystal are presented,induced by the high energy focused the electron beam.The W/WO₃ core-shell spheres are prepared by heating W nanoparticles under 400?for 5 h.The W/WO₃ core-shell sphere is irradiated by a converged electron beam,and the formation or deposition of WO_2.72 nanorods and WO_2.72 nanosheets is observed at the edge and periphery of the sphere.The WO_2.72 is reduced into W with a bcc structure under further irradiation.The orientation relationship between WO_2.72 and W is[001]_WO2.72//[111]_W,(010)_WO2.72//(0 11)_W.This paper provides a simple method to obtain high crystallinity WO_2.72 and combines its crystal structure to investigate the reduction behavior under the electron beam irradiation.