Effects Of W And Eu Doping And Annealing On The Properties Of Thermochromic Vanadium Dioxide

Vanadium dioxide?VO₂?is a transition metal oxide with metal-insulator phase transition?MIT?properties.Its unique phase transition properties make it have a wide application prospect in many fields,but its practical application is limited by the high phase transition temperature.The rutile phase of metallic VO₂ at high temperatures is found on a simple tetragonal lattice?space group P42/mnm?,which is a body-centered orthogonal parallelepiped structure.However,the semiconducting phase of VO₂ at low temperatures belongs to the monoclinic crystal system?space group P21/c?.The metal-insulator transition?MIT?in VO₂ is a first-order reversible transformation with changes in crystal volume at the critical point of the phase transition,which takes place between the semiconducting monoclinic phase at lower temperatures and the metallic rutile phase at higher temperatures.In this paper,VO₂ was successfully prepared by hydrothermal method,and the phase transition temperature of VO₂ and the optical properties of infrared and ultraviolet were adjusted by annealing,single ion doping?W doping?and multiple ion doping?W-E co-doping?.Firstly,VO₂ was prepared by hydrothermal method through the reduction of V2O5 by acetic acid.The analysis of XRD,SEM,TEM and other test results showed that the prepared product was VO₂?B?,which showed regular lamellar structure with high purity and crystallinity.Because VO₂?B?would be converted VO₂?R?only when the temperature is above 450 ?,the samples were annealed at 450?,500? and 550? respectively.XRD and DSC results show that after being annealed,VO₂?B?was transferred into VO₂?M?with the phase transition temperature of 67.8?.In order to further reduce the phase transition temperature of VO₂?M?and improve its transmittance and reflectance to infrared light and ultraviolet light,VO₂?M?was doped with a single kind atom?W?and with a diatomic atom?W-Eu?.With W doping,the microstructure and morphology of VO₂?M?has changed a lot,and the phase transition temperature was reduced from 67.8? to 10.6?.While after W doping,the infrared transmittance was reduced to some extent.After W-Eu co-doping,the microstructure and morphology of the VO₂?M?was also changed dramatically and t'he phase transition temperature was reduced by an average of 15?.In addition,the maximum infrared transmittance was increased from 53.64%to 76.48%.After being doped and annealed,the phase transition temperature and infrared properties of VO₂ have been improved to some extent,which has certain reference value for it s practical application.