Synthesis, charge transport studies, and microwave shielding behavior of nanocomposites of polyaniline with Ti-doped c-Fe 2 O 3 S. Anoop Kumar • Avanish Pratap Singh • Parveen Saini • Fehmeeda Khatoon • S. K. Dhawan Received: 15 June 2011 / Accepted: 19 October 2011 / Published online: 8 November 2011 Ó Springer Science+Business Media, LLC 2011 Abstract This article reports the synthesis, charge transport studies, and microwave shielding properties of polyaniline–Ti-doped c-Fe 2 O 3 nanocomposite. The com- posite has been prepared by the in situ chemical oxidative polymerization using dodecylbenzenzesulfonic acid as a dopant. These resulting polymer composites have been found thermally stability up to 260 °C with magnetization value of *10 emu/g. The temperature dependence of electrical conductivity reveals the applicability of Mott’s 3D-VRH model. The composites has shown the shielding effectiveness of 35.64–45.20 dB ( [ 99.99% attenuation) in 12.4–18 GHz (Ku-Band) frequency range. The enhance- ment of SE has been due to combination of dielectric and magnetic losses leading to decrease in skin depth increase in total (r T ) conductivity and better matching of input impedance. Introduction Electromagnetic (EM) shielding represents a way toward the improvement of the electromagnetic compatibility (EMC). It attracts great attention because of wide and extensive use of electronic equipments like cellular phones, Television, radar etc. that operates in the microwave band. An unnecessary interruption emitted from an external source carrying transient currents from these instruments called electromagnetic interference (EMI) and it severely affect the life and performance of the electrical circuit due to electromagnetic (EM) radiation [1, 2]. Therefore some protection mechanism must be provided to guard these equipments from harmful effect of these EM noises. For the commercial applications material with shielding effectiveness (SE) greater than 30 dB is sufficient, while for defense application, the requirement are significantly higher i.e. between 80 and 100 dB. The enhancement of microwave absorption comes mainly from the combination of magnetic and dielectric losses as well as moderate conductivity of the shield material. At high frequency, the permeability of the magnetic material decreases due to the eddy current losses developed by the EM wave. Therefore, it is better to use conducting polymer matrix to suppress the eddy current phenomenon to enhance the effective inter- action with the absorber. Intrinsic conducting polymers (ICPs) having extended p-conjugated system with con- ductivity in semiconductor regime has emerged as a potential class of materials for EMI shielding and micro- wave absorbers [3–7]. Many research groups are working on this aspect of conjugated polymers, as unlike metals, they not only reflect the EM radiation but also absorb them. The properties of conducting polymer (polyaniline) not only depend on the oxidation state but also on its proton- ation state/doping level and also on the nature of dopants. Polyaniline (PANI) demonstrates a distinctive feature in the sense that it is not charge conjugation symmetric, i.e., the valence and conduction bands are asymmetric to a great extent. As a result, the energy level positions of doping- induced absorptions differ widely from those of the charge Electronic supplementary material The online version of this article (doi:10.1007/s10853-011-6068-5) contains supplementary material, which is available to authorized users. S. Anoop Kumar  A. P. Singh  P. Saini  S. K. Dhawan (&) Polymeric & Soft Materials Section, National Physical Laboratory (CSIR), Dr. K. S. Krishnan Road, New Delhi 110 012, India e-mail: skdhawan@mail.nplindia.ernet.in S. Anoop Kumar  F. Khatoon Department of Applied Sciences, Faculty of Engineering & Technology, Jamia Millia Islamia, New Delhi 110025, India 123 J Mater Sci (2012) 47:2461–2471 DOI 10.1007/s10853-011-6068-5