Solid-state electrochemical sensor for monitoring Mg in Al refining process

Abstract

Novel solid-state electrochemical sensors have been designed using the Mg²⁺ cation conductors incorporating novel solid- state reference electrodes for in-line monitoring of Mg in molten Al during the refining process and also for in-line monitoring of Mg content in molten Al in the alloying process. In this paper we report the preparation of Mg²⁺ ion conductors, MgAl₂O₄ and MgZr₄(PO₄)₆, by the solid state ceramic synthesis route, measurement of their electrical properties using ac-impedance spectroscopy and application of the above cation conductors for designing novel electrochemical sensors for monitoring Mg dissolved in molten Al. The activation energy for Mg²⁺ ion conduction in MgAl₂O₄ is 2.08 eV and in MgZr₄(PO₄)₆ is 1.7 eV, respectively. The sensors have been found to respond rapidly to change in Mg content in molten aluminium around 1000 K.