Structural and Thermal Stability of Sol-Gel Prepared MgHf4P6O24 Solid Electrolyte in Molten Pure Aluminium

The potential solid electrolyte, MgHf4P6O24 was prepared using modified novel sol-gel process. Structural and thermal stability properties of the solid electrolyte were determined. TGA-DSC and HT-XRD analyses indicated that the pure dried xerogel powder, when calcined at 900 oC converts to pure homogeneous single phase MgHf4P6O24 nanopowders with good crystallinity. Pellets of 13 mm diameter and 3.8 mm thickness made by uniaxial compression were sintered at 1300 oC. XRD analysis indicated that the crystalline phase is monoclinic, with a crystallite size of approximately 42 mm. The sintered pellets were stable in the temperature range from 1000 oC to 1300 oC, with no trace of coexistent second phase peaks at higher temperatures. Relative density analysis of MgHf4P6O24 pellets yielded an optimum density and porosity of about 98% and 2%, respectively at 1300 oC. The dense pellet, dipped into pure molten Al at 700±5 oC for 8 h, exhibits impressive structural and thermal stability, showing no single trace of extraneous phase formation. This portrays MgHf4P6O24 as a solid electrolyte with suitable application in high-temperature electrochemical devices.