Dielectric and magnetodielectric properties of Bi0.95Tb0.05Fe0.95Co0.05O3 nanoparticles

Abstract: The structural and morphological analysis of TiO2-V2O5 nanocomposite has been performed using FTIR, XRD and FESEM. Temperature (300 K-500 K) and frequency dependent dielectric properties and complex impedance analysis have been carried out to investigate the effect of grain and grain boundary of the synthesized sample. The electrochemical properties like cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) rate and electrochemical impedance (EIS) of the electrode material have also been investigated. The maximum specific capacitance (Cm) obtained from cyclic voltammetry (CV) and GCD measurement are 262 Fg-1 at scan rate 2 mV s−1 and 251.5 Fg-1 at current density 0.09 mA cm−2 respectively. The stability of the electrode material is measured up to 1000 cycles. The correlation between the dielectric properties and electrochemical properties is successfully demonstrated for the first time. Large grain boundary resistance played an important role for low specific capacitance value at room temperature.

Abstract: Multiferroic magnetoelectric materials, which simultaneously exhibit ferroelectricity and ferromagnetism, have recently stimulated a sharply increasing number of research activities for their scientific interest and significant technological promise in the novel multifunctional devices. Natural multiferroic single-phase compounds are rare, and their magnetoelectric responses are either relatively weak or occurs at temperatures too low for practical applications. In contrast, multiferroic composites, which incorporate both ferroelectric and ferri-/ferromagnetic phases, typically yield giant magnetoelectric coupling response above room temperature, which makes them ready for technological applications. This review of mostly recent activities begins with a brief summary of the historical perspective of the multiferroic magnetoelectric composites since its appearance in 1972. In such composites the magnetoelectric effect is generated as a product property of a magnetostrictive and a piezoelectric substance. A...

Abstract: Single-phased ferroelectromagnet BiFeO3 ceramics with high resistivity were synthesized by a rapid liquid phase sintering technique. Saturated ferroelectric hysteresis loops were observed at room temperature in the ceramics sintered at 880 °C for 450 s. The spontaneous polarization, remnant polarization, and the coercive field are 8.9 μC/cm2, 4.0 μC/cm2, and 39 kV/cm, respectively, under an applied field of 100 kV/cm. It is proposed that the formation of Fe2+ and an oxygen deficiency leading to the higher leakage can be greatly suppressed by the very high heating rate, short sintering period, and liquid phase sintering technique. The latter was also found effective in increasing the density of the ceramics. The sintering technique developed in this work is expected to be useful in synthesizing other ceramics from multivalent or volatile starting materials.

Abstract: Ba doped BiFeO3 compounds were prepared by a solid-state reaction. X-ray diffraction showed that Bi1−xBaxFeO3 was single phase up to x=0.25. These samples exhibited magnetism and ferroelectricity simultaneously at room temperature. The magnetoelectric coupling was evidenced by the increase of the dielectric constant with the increase of the applied magnetic field. For Bi0.75Ba0.25FeO3 with ΔH=8kOe, the values of [er(H)−er(0)]∕er(0) are 1.7% and 1% for 80 and 300K, respectively.

Abstract: We describe systematic studies on Nd and Mn co-doped BiFeO3, i.e., (Bi0.95Nd0.05)(Fe0.97Mn0.03)O3 (BNFM) polycrystalline electroceramics. Raman spectra and X-ray diffraction patterns revealed the formation of rhombohedral crystal structure at room temperature, and ruled out structural changes in BiFeO3 (BFO) after low percentage chemical substitution. Strong dielectric dispersion and a sharp anomaly around 620 K observed near the Neel temperature ( TN ∼ 643 K of BFO) support strong magneto-dielectric coupling, verified by the exothermic peak in differential thermal data. Impedance spectroscopy disclosed the appearance of grain boundary contributions in the dielectric data in the region, and their disappearance just near the Neel temperature suggests magnetically active grain boundaries. The resistive grain boundary components of the BNFM are mainly responsible for magneto-dielectric coupling. Capacitive grain boundaries are not observed in the modulus spectra and the dielectric behavior deviates from the ...

Abstract: Ti-substituted BiLaFeO3 ceramics having compositions Bi0.8La0.2Fe1?xTixO3 (x?=?0.0, 0.05, 0.1, 0.15) were synthesized by the conventional solid-state reaction method. Powder x-ray diffraction investigations performed at room temperature show that the crystal structure is rhombohedral for x?=?0.0, 0.05; tetragonal for x?=?0.15; and a phase boundary occurs at x?=?0.1. In the Rietveld refinement good agreement between the observed and calculated pattern was observed. Dielectric response of these samples was analysed in the frequency range 1?kHz?5?MHz at different temperatures. A decrease in the values of real (??) and imaginary (??) parts of dielectric constant with Ti substitution indicates reduced conductivity and hence enhanced resistivity in doped samples. Stability of dielectric constant and conductivity with temperature is considerably improved with Ti substitution. Magnetic measurements were carried out at room temperature up to a field of 20?kOe. Magnetic properties of Bi0.8La0.2FeO3 ceramics are considerably improved on Ti substitution along with a significant opening in the room temperature M?H hysteresis loop. Higher values of remanent magnetization (Mr) 0.1373 and 0.1487?emu?g?1; coercivity (Hc) 4.856 and 5.904?kOe are observed for samples with x?=?0.1 and 0.15, respectively. This is due to the structural phase transition from rhombohedral to tetragonal.