Effect of MnO2 additive on the dielectric and electromagnetic interference shielding properties of sintered cement-based ceramics

Cement-based ceramic pellets were prepared and their properties were studied for electromagnetic interference (EMI) shielding applications. The shielding materials were made of Portland cement with the addition of different concentrations of manganese oxide (MnO2) up to 10 wt%. The pellets were sintered at 850 degrees C for 5 h and then polished prior to characterizations of density, porosity, microstructures, dielectric properties, and EMI shielding effectiveness (SE). Results show that the MnO2-cement pellets have good dielectric properties, i.e. high dielectric constant (similar to 300) and low dielectric loss (<0.3). The dielectric constant increased with increasing MnO2 content in the cement matrix. The SE values of the MnO2-cements fluctuated between 2 dB and 9 dB in the frequency range of 8-13 GHz. The sample with 10 wt% MnO2 additive had SE values of up to 9 dB. Most of the samples with high additive concentrations produced SE exceeding 7 dB. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.