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A simple hydrothermal technique and in-situ chemical oxidative polymerization of pyrrole monomer yield the functionalized NiO@C@PPy nanomaterial for electromagnetic shielding applications. The crystal structure, morphology, dielectric and electromagnetic shielding (EMI) performance in the X-band (8.2-12.4 GHz) is thoroughly studied. Impedance spectroscopy is utilized to study the electrical response of a NiO@C@PPy pellet. This study focuses on the modulations of relaxation time with frequency at different temperatures. In the NiO@C@PPy composite, a semiconductor-to-metal transition (SMT) is observed, at 328 K. The conduction mechanism of NiO@C@PPy is explained based on the carrier hopping transport model in Ni 2+ and Ni 3+ ions. It is evident from the activation energy value (Ea ≈ 0.32 eV) determined from impedance, conductivity, and dielectric data that the relaxation and conduction processes correspond to the same electro-active region. Using the variable range hopping (VRH) model localization length of the carrier is calculated to be 1.56 Å. The NiO@C@PPy sample demonstrated enhanced conductivity and low dielectric values which are vital in EMI shielding applications. Consequently, the electromagnetic interference shielding effectiveness is found to be 21.9 dB of NiO@C@PPy in the X-band frequency range. This composite material is a good candidate for high frequency shielding applications., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors. Published by Elsevier Ltd.)

High dielectric constant materials are of particular current interests as indispensable components in transistors, capacitors, etc. In this context, there are emerging trends to exploit defect engineering in dielectric ceramics for enhancing the performance. However, demonstrations of similar high dielectric performance in integration-compatible crystalline films are rare. Herein, such a breakthrough via the functionalization of donor-acceptor dipoles by compositional tuning in GaCu codoped ZnO films is reported. The dielectric constant reaches ~200 at 1 kHz and the optical transmittance in visible light reaches ~80%. Importantly, by analyzing the impedance spectroscopy data, prominent relaxation mechanisms in correlation with the dipole properties, enabling consistent explanations of the dielectric constant as a function of frequency are discriminated. The atomistic nature of the dipoles is revealed by the systematic X-ray spectroscopy analysis. Spectacularly, similar trends for the dielectric properties are observed, while synthesizing samples by pulsed laser deposition and ion implantation, indicating the general character of the phenomena., (© 2022 Wiley-VCH GmbH.)