• Kiran Kumari

      Articles written in Bulletin of Materials Science

    • Studies of structural and dielectric properties of Ba5BiTi3Nb7O30 ceramics

      H Sharma Kiran Kumari S N Giri

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      The polycrystalline samples of Ba5BiTi3Nb7O30 (hereafter BBTN) belonging to ferroelectric oxide family of tungsten bronze structure were prepared by high temperature solid-state reaction method. Preliminary X-ray analysis of the samples provided the lattice parametersa=11·9331 Å,b=14·9684 Å, andc=7·0193 Å, and also formation of a single-phase orthorhombic structure at room temperature (303 K). Detailed studies of dielectric constant (ε) and loss (tanδ) as a function of frequency (500 Hz to 10 KHz) at room temperature and also as a function of temperature (liquid nitrogen to 160°C) show the dielectric anomaly and structural phase transition at 16·8°C.

    • Synthesis, structure and characterization of ceramic Ca4Bi2Ti4Nb6O30

      H Sharma Kiran Kumari L S Singh R N P Choudhary

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      The polycrystalline samples of Ca4Bi2Ti4Nb6O30 (herein designated CBTN) were synthesized by the conventional ceramic method. Preliminary X-ray structural study of the compound showed the formation of a single phase solid solution having orthorhombic structure in the paraelectric phase. Measurements of the dielectric constant (𝜀') and dielectric loss (tan 𝛿) as a function of temperarure (-180-200°C) at 1 kHz and 10 kHz and also as a function of frequency (102 Hz to 104 Hz) at five different temperatures [-180°C, -40°C, -10°C, 26°C (room temperature) and 75°C] have shown a dielectric anomaly and a phase transition at -13 ± 1°C in CBTN.

    • D.C. conductivity and spectroscopic studies of polyaniline doped with binary dopant ZrOCl2/AgI

      Kiran Kumari Vazid Ali Anand Kumar Sushil Kumar M Zulfequar

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      Aqueous binary dopant (ZrOCl2/AgI) is used in different ratios such as 1:1, 1:2 and 2:1 (w/w) for chemical doping to enhance the conductivity of synthesized polyaniline (PANI). The doping of polyaniline is carried out using tetrahydrofuran as a solvent. Doped samples are characterized using various techniques such as 𝐼–𝑉 characteristics, UV-visible spectroscopy, X-ray diffractometry (XRD), FTIR and photoluminescence (PL) studies. A significant enhancement in d.c. conductivity has been observed with the introduction of binary dopant. UV-visible study shows that optical parameters change considerably after doping. Interestingly, both direct and indirect bandgaps are observed in the doped samples. XRD patterns show the semi-crystalline nature of doped polyaniline. FTIR study shows structural modifications in functional groups with doping in PANI. Photoluminescence spectra exhibit emission properties of the samples.

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