Processing and Application of Ceramics 2019 Volume 13, Issue 4, Pages: 387-400
https://doi.org/10.2298/PAC1904387S
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Giant dielectric response in microwave processed CaCu3Ti4O12 ceramics: A correlation among microstructure, dielectric and impedance properties
Samanta Buddhadev (Department of Physics & Astronomy, National Institute of Technology, Rourkela, Odisha, India)
Nanda Dipika (Department of Physics & Astronomy, National Institute of Technology, Rourkela, Odisha, India)
Kumar Pawan (Department of Physics & Astronomy, National Institute of Technology, Rourkela, Odisha, India)
Sahu Rashmirekha (Department of Physics & Astronomy, National Institute of Technology, Rourkela, Odisha, India)
Swain Sujata (Department of Physics & Astronomy, National Institute of Technology, Rourkela, Odisha, India)
Mahapatra Apurba (Department of Physics & Astronomy, National Institute of Technology, Rourkela, Odisha, India)
Polycrystalline CaCu3Ti4O12 (CCTO) ceramics was synthesized by microwave
assisted solid-state reaction. Effect of sintering at different temperatures
on the crystal structure, dielectric and impedance properties was
investigated in detail. Rietveld analysis of X-ray diffraction data
identified that crystal structure was a mixture of cubic CCTO and monoclinic
CuO phases. Lattice parameters and amount of CuO secondary phase were also
estimated as a function of sintering temperature. Microstructural
investigation confirmed the existance and successive increase of the melted
phase near the grain boundary region with increasing temperature of
sintering. Cu-rich nature of the melted phase was further confirmed by
selective area EDX spectra. Dielectric and impedance properties were studied
as a function of frequency (100Hz to 1MHz) and temperature (room temperature
to 300°C). Improvement in dielectric properties as a function of sintering
temperature (1000 to 1050°C) was explained in terms of reduction in grain
boundary dimension due to the successive increase in Cu-rich melted phase.
However, dielectric constant started falling when sintered at 1075°C, which
may be accounted in terms of segregation of large amount of CuO phase after
a certain temperature and hence a non-stoichiometry of Cu in CCTO lattice.
Impedance data were modelled by equivalent electrical circuits to
investigate different contributions of electrically heterogeneous systems.
In addition, probable relaxationmechanism has been discussed on the basis of
impedance and modulus data. Activation energies were calculated from
different characterizations and a non-Debye-type relaxation phenomena were
observed. In this work, an attempt is made to build up a correlation among
synthesis procedure, sintering temperature, dielectric, impedance and
microstructural properties.
Keywords: CaCu3Ti4O12, microwave processing, structure, dielectric properties, impedance spectroscopy