Dielectric properties of Bi-substituted LDHs synthesized by co-precipitation and sol-gel methods

Magnesium-aluminium-bismuth layered double hydroxides (Mg3Al1-xBix; LDHs) were prepared using both co-precipitation and sol-gel methods. For the preparation of Mg/Al/Bi LDH by the co-precipitation method, the dissolved appropriate amount of starting materials (Al(NO3)3.9H2O, Mg(NO3)2.6H2O and Bi(NO3)3.5H2O) was mixed with a solution of NaHCO3:NaOH. In the sol-gel processing, the precursor Mg-Al-Bi-O gels were synthesized using the same starting materials and ethylene glycol as complexing agent. The obtained mixed-metal oxides obtained by subsequent heating of Mg-Al-Bi-O gels at 650 °C were reconstructed to Mg3Al1-xBix LDHs in water at 80°C. All the synthesized products were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and dielectric measurements.