Rapid sol–gel synthesis of honeycomb-layered Na3Ni2BiO6 and orthorhombic Na3Ca2BiO6

Abstract

The A₃M₂M′O₆ type materials Na₃Ca₂BiO₆ and Na₃Ni₂BiO₆ 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 Na₃Ca₂BiO₆ 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 Na₃Ca₂BiO₆ exhibits only weak, temperature independent paramagnetism. Na₃Ni₂BiO₆ was found to be antiferromagnetic, with a Néel temperature of 12 K, in line with previously reported results.