Properties of nasicon electrolytes prepared from alkoxide derived gels: Ionic conductivity,durability in molten sodium and strength test data

Nasicon ceramics have been prepared from gel-derived raw materials both by conventional sintering and by hot-pressing. For several compositions the ionic conductivity have been determined by the AC-method. The properties of ceramics based on the ZrO₂-poor composition Na_2.94Zr_1.49P_0.8Si_2.2O_10.85 have been studied in greater detail. Durability test in Na/Na-cells so far indicate good stability at 300°C, and corrosion tests in molten sodium (400°–700°C) indicate that at 400°, 350° and 300°C it will take respectively at least 100 h, 7 weeks and 3 years to dissolve a 1 micron thich layer of the ceramic. The fracture strenght of the ceramics have been determined by the three point bending method. Weibul statistics indicate an average fracture strength of 168 MPa and a m-value of 8.3 (sample vol. 0.07 cm³) for the best ceramics prepared so far.