Spray-drying and fabrication of superionic conducting sodium rare-earth silicates

Abstract

Fine precursor powders of particle diameter of 0.50–7 μm and high surface area (9 m 2/g) for superionic conducting Na 5RESi 4O 12 (RE=Gd, Y) were successfully produced by spray-drying and an optimised calcination procedure. Using these powders, dense sinters (>98% of theoretical) with ƒ(NGS) or ƒ( NGS)=1.0 (the proposed parameter for purity) were obtained under normal sintering conditions. 300°C ionic resistivities were calculated from ac impedance and had values of 5.6 Ω cm with an activation energy for conduction of 4.5 kcal/mol for Na 5GdSi 4O 12 and 7.7 Ω cm and 5.9 kcal/mol for Na 5YSi 4O 12. These values were dependent on the ƒ(NGS) or ƒ(NYS).