Rare earth ion-infused -MnO₂ nano-rods for excellent EMI shielding efficiency: Experimental and theoretical insights

In this communication, for the first time rare earth elements like Gd3+ and Er3+ ions are impregnated into the alpha-MnO(2)tunneled structure involving the modified chemical synthesis route followed by hydrothermal technique. X-ray diffraction patterns and Raman spectroscopy confirm the proper phase formation without any impurity. A theoretical in-depth DFT study for the electronic bands and variation of density of states with the infusion of rare earth elements into the host structure confirms the experimental findings and depicts the suitability of the material for the EMI shielding application. The novel synthesis technique helps to achieve uniform nanorod formation with a high specific surface area. Doping-induced defects, high surface-to-volume ratio, Maxwell-Wagner-Siller interfacial polarization, etc. lead to achieving high dielectric response with moderate tangent loss at a frequency range of 40 Hz to 1 MHz. Temperature-dependent dielectric behavior indicates the paramagnetic to ferromagnetic transition at 120 degrees C and 70 degrees C for the Gd- and Er-doped alpha-MnO2 samples respectively. The electromagnetic interference (EMI) shielding effectiveness (SE) has achieved a maximum of -43 dB at 15.3 GHz and - 46 dB at 15.3 GHz for Gd- and Er-doped alpha-MnO2 thin layer of thickness similar to 600 mu m respectively. Higher dipolar polarization, loss tangent, conductive pathways, and defects inside the crystal lead to attaining a high EMI shielding efficiency. This result reveals >99.997% EMI SE against the hazardous electromagnetic waves in the microwave/GHz frequency region.