Elechtrochemical Synthesis of Chromogeic RE Doped Vanadium Oxide Films in Molten Salt

 Yoshikazu KANEKO

Faculty of Engineering, Yamanashi University Kofu, Yamanashi, 400-0016, Japan  

The  vanadium oxides  films show multicolored electrochromism, the  oxidation color is orange and the reduction color is  blue green  by  alternating the potential.  Recently, the  electrolytic deposition method  has been actively investigated as a powerful technique for the large area chromogenic(EC) thin film. The synthesis experiments have been done in  aqueous solution[1].  The EC rare earth element(RE) oxides of praseodymium films formed by MOCV ware reported [2]. The RE(Pr,Nd,Eu,Ce) ion doped vanadium oxide films were synthesized on the ITO electrode by electrolysis in molten dimethylsulphon(DMSO2)-RECl3, DMSO2-RECl3-LiNO3, DMSO2-RE2O3, DMSO2-RE2O3-V2O5 and bisulfate(NH4HSO4)-RE2O3-V2O5 systems at  the   temperature   about  150-250℃. The  RE element and vanadium   content   in   melts  was  analyzed   by   ICP. The solubility of praseodymium in DMSO2-PrCl3system was 2.4mg /1g DMSO2 at 150℃. The obtained films  were analyzed by x-ray diffraction, IR absorption spectra and SEM micrograms. Moreover, the EC reactions   of  the RE doped vanadium   bronze   films    in   room   temperature   solution   of  propylene carbonate   or    high  temperature solution   of  DMSO2   were  investigated. The amount of the soluble RE ions was considerably increased by the addition of vanadium oxides in molten salt. This increase of solubility was attributed to the acid-base and redox reaction between vanadium oxides and RE oxides in molten salts.  The good effect of addition of alkaline nitrates for formation of RE ion doped vanadium bronze films by electrolysis was observed. The luminescence thermochromic  and electrochromic properties of RE ions doped vanadium bronze films were measured. The intensity of the luminescence peaks at 470 nm,535 nm for vanadate ions were increased by doping RE ions.  The  absorption spectrum of praseodymium oxide  films  obtained by electrodeposition in DMSO2-Pr6O11-LiNO3 systems had 640 nm and 410nm peaks due to mixed valence of Pr3+andPr4+. The RE ion doped vanadium oxide  films were discussed  on  the  basis   for   high  temperature   electrochromic   and luminescence thermochromic materials.    

 

[1]Y.Kaneko,Jintie  Li  and   Lu   Chen, Denki Kagaku  (presently  Electrochemistry),   66,   1323(1998).                                                            

[2] G.R.Thomas and J.R.Owen,Solid State Ionics, 53-56, 513(1992).

 

 

 

The films of rare earth bronze and rare earth ions doped vaanadium bronze on ITO electrodes were obtained by electrolysis in a molten NH4HSO4-LiNO3-EuCl3 orNdCl3system,NH4HSO4-NH4VO3 -LiNO3-EuCl3system, at 300 and DMSO2-PrCl3system,DMSO2-PrCl3-V2O5system,DMSO2-PrCl3 -LiNO3system, DMSO2-Pr6O11-NH4VO3system, at 150℃, respectively. The amount of the soluble rare earth metal ions was considerably increased by the addition of vanadium oxides in molten salt. This increase of solubility was attributed to the acid-base and redox reaction between vanadium oxides and rare earth metal oxides in molten salts.  The good effect of addition of alkaline nitrates for formation of rare earth  ions doped vanadium bronze films by electrolysis was observed. The luminescence thermochromic  and electrochromic properties of rare earth ions doped vanadium bronze films were measured.The intensity of the phosphorescence peaks at 470 nm,535 nm for VO3+ and forVO2+were increased