Dielectric properties of nano ZnO-polyaniline composite in the microwave frequency range

doi:10.1016/j.jallcom.2008.10.004

Journal of Alloys and Compounds

Volume 477, Issues 1–2, 27 May 2009, Pages 370-373

https://doi.org/10.1016/j.jallcom.2008.10.004 Get rights and content

Abstract

Films of polyaniline (PANI) and PANI-nano ZnO composites have been synthesized by solution casting technique. Fourier transform infrared spectroscopic studies of PANI and PANI-nano ZnO composite films indicated the presence of interaction between nano ZnO particles and molecular chains of PANI. Dielectric properties of the PANI and composite films have been investigated in the frequency range of 8.0–12.0 GHz. The real part of permittivity (ɛ′) and loss factor (tan δ) were found to decrease in PANI-nano ZnO composite films. The decreasing behavior of ɛ′and tan δ may be attributed to the interaction between nano ZnO particles and PANI molecular chains. The interaction between PANI chains and surface of ZnO nano particles restricts the motion of the dipoles and leads to the decrease of ɛ′and tan δ of the composite films.

Introduction

The development of nano inorganic/polymer composite material has been receiving significant interest due to wide range of potential applications of these composites in optoelectronic devices [1], [2], [3], [4] and electromagnetic interference (EMI) shielding [5], [6]. These have shown a synergetic behavior between the polymer and inorganic material [7], [8]. At nano scale the surface to volume ratio is large and thus the inorganic material in the nano form is expected to modify the electrical, optical and dielectric properties of the polymer by a significant amount.

ZnO, a semiconducting material having direct wide band gap (3.37 eV) and large exciton binding energy (60 meV) at room temperature is very promising for optoelectronic devices [9], [10]. Whereas polyaniline (PANI) is a widely studied polymer due to good environmental stability [11], [12], tunable conductivity and its relative ease in preparation. Since polyaniline and nano ZnO both are having a wide range of technological applications so the hybrid of PANI-nano ZnO is believed to show novel properties due to the molecular level interaction between nano ZnO and PANI molecular chains. There are few reports on the synthesis, morphological, electrical and optical studies [13], [14] of PANI-nano ZnO composite. Studies of dielectric behavior in microwave region are very important for assessing its potentiality to use it for electromagnetic interference (EMI) shielding and telecommunication applications. A low dielectric constant is often desirable for applications such as high-speed integrated package and satellite applications.

In this paper we report the synthesis of PANI-nano ZnO composite films and the study of their dielectric behavior in microwave region (8.0–12.0 GHz). The dielectric constant and loss factor of PANI-nano ZnO composite is found to decrease by the incorporation of nano ZnO in PANI matrix.

Section snippets

Experimental details

Polyaniline (PANI) was synthesized by chemical oxidative polymerization of aniline in the presence of HCl using ammonium peroxidisulphate. One liter solution consisting of 0.1 M of aniline, 1.0 M of HCl in distilled water was stirred in a double wall flask at 1 °C for 5 h. During the stirring, 0.1 M solution of ammonium peroxidisulphate was added drop by drop. After 6 h of stirring, the solution was filtered in Butchner funnel (G-4) and the residual was washed 3–4 times with double distilled water

X-ray diffraction (XRD) analysis

Fig. 1 shows the XRD patterns of pure polyaniline in the emeraldine base form, zinc oxide (ZnO) nano powder and PANI-nano ZnO nano composites (PZ1 and PZ2). The XRD pattern of PANI shows a broad peak at 2θ = 19.8° which corresponds to (2 0 0) plane of PANI [15]. This broad peak in the XRD pattern of PANI shows that it has some crystallinity. The crystallinity of PANI can be ascribed to the repetition of benzenoid and quinoid rings in PANI chains [15]. The XRD patterns of nano ZnO powder, PZ1 and

Conclusions

Films of polyaniline and PANI-nano ZnO composites were synthesized by solution casting technique. Study of transmission electron microscopy revealed the synthesis of ZnO nano particles of sizes ∼15–20 nm and their dispersion in PANI matrix. FTIR spectra revealed that the characteristic absorption peaks of PANI shifted by a significant amount for PANI-nano ZnO composite films. The dielectric constant and loss factor of PANI were found to decrease in PANI-nano ZnO composites (PZ1 and PZ2). The

Acknowledgments

Financial support from CSIR is gratefully acknowledged. One of us (Bhupendra K. Sharma) is thankful to CSIR, New Delhi, India for awarding the Junior Research Fellowship.

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Dielectric properties of nano ZnO-polyaniline composite in the microwave frequency range

Abstract

Introduction

Section snippets

Experimental details

X-ray diffraction (XRD) analysis

Conclusions

Acknowledgments

Thin Solid Films

Mater. Sci. Eng. B

Appl. Surf. Sci.

Synth. Met.

Synth. Met.

J. Magn. Magn. Mater.

Mater. Res. Bull.

Chem. Phys. Lett.

Adv. Funct. Mater.

Appl. Phys. Lett.

Appl. Phys. Lett.