Effect of LiF on the ion conductivity and sinterability of (Al0.2Zr0.8)20/19Nb(PO4)3 solid electrolyte

Abstract

The (Al0.2Zr0.8)20/19Nb(PO4)3 was fabricated by high temperature solid reaction method, and the sintering property and electrochemical property of the electrolyte were improved by adding LiF as a sintering aid. The phase composition, microstructure and electrical conduction property of the (Al0.2Zr0.8)20/19Nb(PO4)3 were analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The results show that the compactness of electrolyte was improved by LiF addition. When the addition amount of sintering aid LiF is 4 wt%, the electrolyte has the highest density and conductivity, and its conductivity reaches 2.45 × 10−3 S.cm−1 at 500 °C, which is 11.1 times as high as that of sample without LiF addition. The ionic transfer numbers of the electrolyte measured by DC polarization method are above 0.999, indicating that the solid electrolyte nearly is pure Al3+ ion conduction and the electronic conduction may be ignored. On the basis of (Al0.2Zr0.8)20/19Nb(PO4)3 with 4 wt% LiF electrolyte and CrVO4 sensing material, a mixed potential type of NH3 gas sensor was prepared and tested. The NH3 gas sensor displays excellent sensing performance with a sensitivity of 90.2 mV/decade at 300 °C.