Kajal Parashar

Electrical properties of bulk and nano Li 2 TiO 3 ceramics: A comparative study

Nanocrystalline and bulk Li2TiO3 having monoclinic structure were prepared by mechanical alloying as well as conventional ceramic route. Complex impedance analysis in the frequency range of 100 Hz-1 MHz over a wide range of temperature (50–500 °C) indicates the presence of grain boundary effect along with the bulk contribution. The frequency-dependent conductivity plots exhibit power law dependence, suggesting three types of conduction in the material: low-frequency (100 Hz-1 kHz) conductivity showing long-range translational motion of electrons (frequency independent), mid-frequency (1–10 kHz) conductivity showing short-range hopping of charge carriers and high-frequency (10 kHz-1 MHz) conductivity showing conduction due to localized orientation of hopping mechanism. The electrical conductivity measurement of nanocrystalline and bulk Li2TiO3 with temperature shows the negative temperature coefficient of resistance (NTCR) behavior. The activation energy (0.77 eV for nano sample and 0.88 eV for bulk sample) study shows the conduction mechanism in both samples. The low activation energies of the samples suggest the presence of singly ionized oxygen vacancies in the conduction process.

Impact of divalent dopant Ca2+ on the electrical properties of ZnO by impedance spectroscopy

The electrical properties of Zn1−xCaxO (x = 0, 0.01, 0.02 and 0.03) nanoceramics synthesized by solid-state reaction method were investigated by complex impedance spectroscopy (CIS) from room temperature to 500∘C. Structural analysis of the synthesized material using the X-ray diffraction technique suggests that they exhibit a single phase with hexagonal wurtzite structure. Experimental results indicate that the synthesized material shows temperature-dependent relaxation phenomena. The variation of frequency exponent (s) with temperature shows the presence of thermally activated polarization mechanism in the synthesized sample. Dielectric constant was found to decrease with increase in frequency and temperature for Ca-doped samples. Ca-doped ZnO sample shows dielectric loss at lower temperature than that of pure ZnO.

Structural, Electrical and FT-IR Studies of Nano Zn1-xCaxO by Solid State Reaction Method

Single phase polycrystalline with = 0, 0.01 and 0.02 were synthesized by conventional solid state reaction method. The X-ray diffraction shows that the ceramic samples has hexagonal Wurtzite structure with a space group of p63mc and average crystallite size in the range 52 - 88 nm. The dielectric and electrical properties were studied within the temperature range 30 °C to 500 °C under air atmosphere as function of frequency (10 kHz). The electrical properties of grain interior and grain boundary have been studied by using the impedance spectroscopy and follow the non-Debye relaxation process. It was observed that the AC conductivity of ceramic samples following the Universal power law within the frequency range 1kHz to 1 MHz. The activation energy of Pure is 0.29 eV was calculated by using the Arrhenius-relation with in temperature range 300 - 500 °C, which is increased to (0.40 eV ) when = 0.02 of at 10 kHz . The peaks attributed at 1415 cm-1 () and 1413 cm-1 () in FT-IR measurement of are due to Ca-O stretching from the calcite phase of CaCO3, which is not observed in Pure ZnO confirms the presence of Ca in ZnO lattice. Keywords: , FT-IR, Impedance spectroscopy, ac conductivity, Dielectric constant.

Nanoscale Effects on Structural and Giant Dielectric of PZT Synthesized by High Energy Ball Mill

We report the formation of nanostructure Pb(Zr0.53Ti0.47)O3 (PZT) ceramic powder having cubic crystal structure under ambient conditions that has been found to be stable up to 800°C. The cubic structure of nanocrystalline PZT under normal condition is attributed to the crystallite size effect. The crystallite size effect has also reflected its crucial role in substantial enhancement of the dielectric permittvity at Tc that may be termed as a novel “giant dielectric permittivity” (GDP) effect. The origin of such a high permittivity (ϵ∼34600 at 10 kHz), not reported so far, has been traced to the changes occurring in the material microstructure, interface and grain boundary effects predominantly controlled by the crystallite size.