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

Effect of Multiple Substitutions (Pb, Ti, Zr) on Structural, Permittivity and Electrical Properties of BiFeO3 Ceramics

Three complex polycrystalline samples of Bi1-xPbxFe1-x Zrx-yTiyO3,with the combination of (i) x, y = 0.0 (BFO), (ii) x = 0.5 and y = 0.5 (BFPTO)and (iii) x = 0.5 and y = 0.25 (BFPZTO) were prepared by a standard mixed oxide (solid state reaction route) method at optimized calcinations (900oC) and sintering (930-950oC)temperatures. The effect of multiple (Pb, Ti and/or Zr) substitutions of different amount onthe permittivity, impedance and modulus characteristics of the materials has been investigated at different frequencies and temperature. Limitation associated with BiFeO3 (BFO) due to its semiconducting behavior acts as constraint in polling the material at room temperature leading to large dielectric loss. Attempts were made to minimizethe loss by substitution of Pb on the Bi site and Ti and/or Zr at the Fe site of BFO. The study indicates that the phase transition temperature of BFO is lowered,the degree of diffuse phase transition is enhanced and electrical parameters (dielectric constant, electrical resistivity, remnant polarization and maximum polarization) areincreased with a significant reduction in dielectric loss as a consequence of the substitution. Detailed studies of Nyquist plots with impedance and electric modulus data suggest that the existence of non-Debye type of relaxation phenomena in the materials. The ac conductivity study reveals that the conduction mechanism in the material obeys universal Jonschers power law

Studies of electrical conductivity and magnetic properties of Bi1-xGdxFeO3 multiferroics

The polycrystalline samples of Bi1-xGdxFeO3 (x = 0, 0.1, and 0.2) multiferroic oxides have been synthesized by a solid-state reaction/mixed oxide technique. The preliminary X-ray structural analysis with room temperature diffraction data confirmed the formation of single-phase systems. Study of room temperature scanning electron micrograph (SEM) of the surface of the above samples exhibits a uniform distribution of plate- and rod-shaped grains throughout the sample surface with less porosity. The dielectric behavior of the materials was studied in a wide range of frequency (1 kHz–1 MHz) and temperature (30–400°C). The nature of temperature dependence of dc conductivity confirms the Arrhenius behavior of the materials. The frequency–temperature dependence of ac conductivity suggests that the material obeys Jonscher's universal power law. An increase in Gd-content results in the enhancement of spontaneous magnetization BiFeO3 (BFO) due to the collapse of spin cycloid structure. The magnetoelectric coupling coefficient of BFO has been enhanced on Gd-substitution

Effect of La-substitution on structural, dielectric and electrical properties of (Bi0.5Pb0.5) (Fe0.5Zr0.25Ti0.25)O-3

As lead zirconium titanate and bismuth ferrite (BFO), members of perovskite family, have high dielectric constant and ferroelectric/ferromagnetic phase transition temperature, they are used for many potential applications including random access memory, sensors. The present work describes the modifications in the ferroelectric behaviour of PZT doped BFO due to substitution of few molar percent of La on Fe-site. A thorough comparative investigation of the frequency and temperature response of dielectric permittivity, dielectric loss, electric modulus, complex impedance and ferroelectric properties of Bi0.5Pb0.5 [Fe(0.5-x) La-x (Zr0.25Ti0.25)]O-3, where x = 0.0, 0.1, 0.2, 0.3 (hence forth called as BFPZLTO) compounds were studied in a wide frequency range 10 kHz to 1 MHz at temperature range 25-400 degrees C using ac impedance spectroscopy and electric modulus analysis. The structural analysis of compound revealed the tetragonal phase with space group P4 mm at room temperature. Cole-Cole plots are used for interpretation of relaxation mechanism in the materials. The materials especially the compound with x = 0.3 found more suitable to be used in transducers, RAMs, flip-flop memories, etc., for electronics applications