Rapid sol-gel synthesis of honeycomb-layered Na 3 Ni 2 BiO 6 and orthorhombic Na 3 Ca 2 BiO 6 .

The A 3 M 2 M'O 6 type materials Na 3 Ca 2 BiO 6 and Na 3 Ni 2 BiO 6 were successfully synthesised through two sol-gel techniques - a method based on a natural deep eutectic solvent, and a biopolymer-mediated synthesis. The materials were analysed using Scanning Electron Microscopy to determine if there was a difference in final morphology between the two methods, and it was found that the natural deep eutectic solvent method resulted in a more porous morphology. For both materials, the optimum dwell temperature was found to be 800 °C, which in the case of Na 3 Ca 2 BiO 6 was a much less energy-intensive synthesis process than its seminal solid-state synthesis. Magnetic susceptibility measurements were undertaken on both materials. It was found that Na 3 Ca 2 BiO 6 exhibits only weak, temperature independent paramagnetism. Na 3 Ni 2 BiO 6 was found to be antiferromagnetic, with a Néel temperature of 12 K, in line with previously reported results.