Transition metal impregnated nanostructured oxide material for broadband electromagnetic interference shielding: A theoretical and experimental insight

Abstract

In this communication, the electromagnetic interference shielding (EMI) performance and dielectric properties of the high temperature sustainable α-MnO2 semiconductor quantum dots (SQDs) have been modulated by incorporating cobalt ions into its crystal structure by employing a modified chemical synthesis technique as well as post-calcination treatment. The phase and structural investigation confirm the Co atoms are present inside the (2×2) tunnel of α-MnO2 hollandite type network and with the increasing sintering temperature the crystallite size of the samples has been found to be increasing. The theoretical bandgap energy of the samples using generalized gradient approximation with Hubbard U correction term (GGA + U) is found to be in good agreement with the experimental findings. From PL spectra it has been found that the peak locations are shifted because of the variation of the inherent bandgap energy which confirms the particles are quantum dots (QDs) in nature. Gigantic dielectric constant has been observed for the sample CM450 at low frequency (∼0.7 M at 40 Hz) with moderate tangent loss. This enhances the shielding performance (∼48 dB at 17.5 GHz) of the unwanted electromagnetic signals emitted from the daily using electronic gadgets at X-band and Ku-band. Such valuable shielding performance can be ascribed to the dual effect of dipolar as well as Maxwell Wagner Sillars (MWS) interfacial polarization effect. Considering all the performance it can be clearly concluded that the presence of a foreign element like Co creates a remarkable footprint to enhance all the electrical performance of the α-MnO2 SQDs and makes the material highly suitable for high dielectric separator as well as an efficient material for EMI pollution shielding application in electronic industry.