Preparation And Application Of Novel High-valence Cation Conducting Solid Electrolytes

It is generally believed that the conductivity of high-valence cation conducting solid electrolytes is low because of strong electrostatic interaction between the cation and surrounding anions.For the purpose of improving the ion conducting,it is efficacious to introduce other ions in the solid electrolytes with the NASICON-type structure to expand the ion-conductive pathway in the lattice and enhance the sinterability.Different compositions of solid electrolytes with NASICON-type structure,(Al0.15Zr0.85)4/3.85 Nb P3-x Vx O12(0.0?x?0.2),(Al0.2Zr0.8)(4-x)/3.8Nb P3-x Mox O12(0.0?x?0.2)and(Al0.2Zr0.8)(4+2x)/3.8Nb P3-x Bx O12(0.0?x?0.2)were successfully synthesized according to the solid state reaction by partially replacing the P site with V,Mo or B ions.The phase composition and crystal structure were investigated by X-ray diffraction(XRD)and scanning electron microscopy(SEM).The results indicate that the solid electrolytes consist of a NASICON-type structure.Compared with the undoped solid electrolyte,the grains were regularized in size and shape,which demonstrated that the compactness was enhanced.Predominant conducting species in the solid was demonstrated to be Al3+ ion by the dc polarization measurnment and the electron conduction is negligible.The electrical properties of the solid electrolytes prepared by doping have also been greatly improved.(Al0.15Zr0.85)4/3.85 Nb P3-x Vx O12(x=0.1)possesses the conductivity of 2.32×10-3 S·cm-1 at 600?,increasing approximately one order of magnitude than(Al0.15Zr0.85)4/3.85Nb(PO4)3.The conductivity of(Al0.2Zr0.8)(4-x)/3.8Nb P3-x Mox O12(x=0.15)and(Al0.2Zr0.8)(4+2x)/3.8Nb P3-x Bx O12(x=0.1)was c.a.2.38 and 1.09 times higher than that of the undoped(Al0.2Zr0.8)4/3.8Nb(PO4)3,because of the lower activation energy and the higher reactivity probably.The NO2 gas sensor based on(Al0.15Zr0.85)4/3.85 Nb P2.9V0.1O12 solid electrolyte exhibited a rapid and stable response at temperatures as low as 150?.The aluminium sensor based on(Al0.2Zr0.8)3.85/3.8Nb P2.85Mo0.15O12 exhibited a rapid,stable and theoretical response that obeys the Nernst equation at 500?.