Structural, Dielectric and Electrical Characteristic of Bi0.5Pb0.5[Fe0.1La0.4(Zr0.25Ti0.25)]O3

The polycrystalline compound Bi0.5Pb0.5 [Fe0.1La0.4 (Zr0.25Ti0.25)]O3 was synthesized by substituting Pb, La, Zr and Ti ions on perovskite structured bismuth ferrite (BFO) with the help of mixed oxide solid state reaction method. The present work is to observe the effect of off-valence and iso-valence substitution on the dielectric and electric properties of bismuth ferrite (BFO). The room temperature XRD pattern of the calcinated powders of the sample reveals that the crystal structure is tetragonal with space group P4mm, while BFO has rhombohedral structure with space group R3c. The SEM of the sintered pellet of the compound indicates that the small grains are uniformly distributed over the surface. Complex impedance spectroscopy (CIS) was adopted to analyze the dielectric, impedance and conductivity behavior of the compound. The results show that the dielectric loss in the material is significantly less than that of BFO and the dielectric and ferroelectric behavior of the sample get enhanced. The complex impedance plots show the existence of non-Debye type of relaxation phenomena, which is caused by resistive and capacitive effect of the bulk and grain boundaries. The Arrhenius plot for the compound indicates that the material possesses NTCR behavior. The frequency response of ac conductivity obeys Jonschers law and UDR (universal dielectric response).[Key words: off-valence, iso-valence, CIS, non-Debye type relaxation, NTCR, UDR

Structural, dielectric and electrical characteristics of lead-free electro-ceramic:Bi(Ni2/3Ta1/3)O3

A lead-free dielectric material bismuth nickel tantalite Bi(Ni2/3Ta1/3)O3(BNT), is prepared using a standard high-temperature solid-state reaction technique. The formation of a single phase BNT in orthorhombic crystal symmetry has been confirmed through X-ray structural analysis. The observation of nearly uniform and homogeneous distribution of grains with less number of voids on the surface of the pellet sample in scanning electron micrograph exhibits the good quality of the sample. Studies of dielectric parameters in a wide range of frequency and temperature provide important data for applications. The electric response investigated by impedance spectroscopy shows the effect of grains and grain boundaries in the restive and capacitive characteristics of the material. Based on the negative temperature coefficient of resistance (NTCR) characteristics of the material, studied by impedance spectroscopy technique, confirmed the semiconductor characteristics of the material at elevated temperatures. An analysis of Nyquist plots shows the existence of non-Debye type of dielectric relaxation mechanism in the sample. The charge carriers in the compound have both long and short range ordering that are again validated by the complex modulus and impedance analysis of the material. Keywords: Bi(Ni2/3Ta1/3)O3(BNT), Dielectric relaxation, Impedance Spectroscopy, Nyquis

Impedance and modulus spectroscopic studies of lead free Na12 Dy12 TiO3 Ceramic

A lead-free perovskite ceramic, Na12Dy12TiO3 (NDT), was synthesized via the conventional solid state reaction method. The sample’s structural, microstructural, and electrical characterizations were performed over the varying range of frequency and temperature. The detailed electrical behavior of the samples has been analyzed and explored by applying impedance spectroscopy. The structural study confirmed the orthorhombic structure of NDT material, with the presence of a very small contribution of the impure pyrochlore phase. The dielectric permittivity of the sample as a function of temperature shows the ferroelectric to paraelectric phase transition temperature to be ∼94 °C, and the shift of phase transition temperature is attributed to its structure. The frequency and temperature-dependent electrical features are studied within the framework of impedance, modulus, and conductivity spectra. The Nyquist plots detect the contribution of grain/grain boundaries to the inclusive polarizations. The presence of two depressed semicircular arcs in the Nyquist Plots (both grain/grain boundaries contribute to electrical properties) was approached for higher temperatures (≥350 °C), suggesting the relaxation phenomena to be temperature dependent with a distribution of relaxation times. Also, the modulus spectra analysis confirms the temperature-dependent multiple relaxation phenomena to be of the Non-Debye type and is present in the sample at ≥350 °C. The conductivity spectra confirm the presence of dc conduction at ≥350 °C and a temperature-dependent polaron hoping conduction behavior with the validity of Johnscher’s universal law