Novel MgHf4P6O24 as a Solid Electrolyte in Mg-Sensors

Abstract

In this research paper, the results of the ac-electrochemical impedance spectroscopy (EIS) of MgHf4P6O24 solid electrolyte employing a two-probe technique between 182-764oC, and from 100 mHz to 32 MHz have been reported for the first time. The results indicate that MgHf4P6O24 is an excellent Mg2+-cation conducting solid electrolyte. The ionic conductivity of MgHf4P6O24 was found to be 4.52 x 10-4 Scm-1 at 747oC and the material exhibited no signature of phase change unlike the MgZr4P6O24 solid electrolyte during the sintering and impedance measurements suggesting that both materials and operational stability has been successfully maintained at 1000 ≤ T/oC ≤ 1300. In addition to this, the design, fabrication and testing of solid-state electrochemical Mg-sensors incorporating MgHf4P6O24 as a solid electrolyte has been successfully demonstrated in molten Al-Mg dilute alloys for the first time in this study. The high-temperature Mg-sensors were designed using the novel Mg2+-cation conducting solid electrolyte by incorporating a biphasic powder mixture of MgCr2O4 + Cr2O3 + O2 as a solid-state reference electrode, which has shown promising trend after successfully sensing the Mg dissolved in molten Al at 700±5oC.