Magnetodielectric behaviour of composites of NiO-SiO₂ nanoglass and mesoporous silica SBA-15

Nanocomposites with glass composition xNiO-(1-x)SiO₂, having x values as 0.1, 0.2 and 0.4 respectively, were synthesized by sol-gel process within SBA-15 template with ordered pores of diameter ~5 nm. TEM studies revealed the relative position and stoichiometric occupancies of constituent elements. XPS investigation substantiated the presence of Ni²⁺/Ni³⁺ ions in these nanocomposites. These systems exhibited a maximum specific capacity value of 730.7 F/g which was explained using Catalan's model. The maximum change (120%) of magnetodielectric parameter was found to be dependent on proportions of Ni²⁺/Ni³⁺ ions present in the system and therefore on charge storage properties. The structure-dependent interaction and crucial role of Ni³⁺ on charge-storage mechanism have been investigated by DFT accounting for enhanced electrical polarizability. Nyquist plots suggest the presence of two different resistive layers with high knee frequency (155 kHz) in the presence of magnetic field. These materials will be suitable for fabricating magnetically controlled supercapacitor devices.