Assessment of MgZr 4 P 6 O 24 as a Solid

The potential solid electrolyte, MgZr4P6O24, was prepared using a modified sol-gel method. This study aimed to investigate both the structural and electrical properties of the solid electrolyte. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) revealed that pure dried xerogel, when calcined at 900 °C, transforms into single-phase MgZr4P6O24 nanopowder with considerable crystallinity. Pellets, created via uniaxial compression, were sintered at 1300 °C for 24 hours, resulting in a monoclinic crystalline phase with a crystallite size of approximately 40 nm. The sintered pellets exhibited stability between 1000 and 1300 °C, while some minor extraneous peaks suggested the presence of a secondary phase (Zr2P2O9) at elevated temperatures. Impedance spectroscopy measurements determined the electrical conductivity of MgZr4P6O24 to be 7.23 × 10–3 S/cm at 725 °C. Furthermore, the MgZr4P6O24 pellet was successfully employed for the development of a solid-state Mg-sensor for Mg concentration measurement in molten Al at 700 ± 5 °C, using a biphasic powder mixture of MgCr2O4 and Cr2O3 as a ceramic reference electrode. A linear relationship between the electromotive force (emf) and the logarithm of Mg concentration was observed, indicating a transport number of Mg2+ cation in MgZr4P6O24 of 0.85 ± 0.03 at 700 °C, highlighting its potential applications in high-temperature electrochemical sensors.