Effect of intercalated anions on the electrical and dielectric properties of NiAl-X layered double hydroxide (X=CO32-, NO3- and H2PO4-): investigation by impedance spectroscopy

This paper reports the effect of interlayer species on the electrical and dielectric behaviours of a lamellar structure. The successful intercalation of three oxyanions ( CO 3 2 - , NO 3 - and H 2 PO 4 - ) in the interlayer space of NiAl-layered double hydroxide (LDH) was confirmed by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis and inductively coupled plasma. Using complex impedance spectroscopy measurements, equivalent circuit consisting of three serially connected R-CPE units was established for each sample. Each unit contains a resistance and a constant phase element representing contributions of grain, grain boundary and electrode interface, which allowed the determination of their electrical parameters. The adjustment of experimental data of conductivity by the double power law allowed the determination of σ dc and other conductivity parameters, and therefore, the investigation of the effect of intercalated anions on NiAl LDH electrical behaviour. Indeed, dihydrogenophosphates intercalated sample was found to decrease σ ac over the frequency range of measure, comparing to the other anions. The intercalation of this anion has also an effect on dielectric properties, it reduces the value of dielectric constant of NiAl LDH, and shifts the maximum of tan δ towards medium frequencies with a decrease in the value of loss tangent above 10 5 Hz. Carbonate and nitrate intercalated LDH showed a similarity in their effect on electrical and dielectric properties of NiAl LDH.