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.