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The multiferroic composites of ferromagnetic Li0.1Ni0.2Mn0.6Fe2.1O4 (LNMFO) and ferroelectric Bi0.8Dy0.2FeO3 (BDFO) with the general formula xLi0.1Ni0.2Mn0.6Fe2.1O4–(1 − x) Bi0.8Dy0.2FeO3 have been prepared by the solid-state reaction route. The XRD analysis has ensured that the composites are composed of a mixture of cubic spinel LNMFO and orthorhombic perovskite BDFO phases. Field Emission Scanning Electron Microscope is used to investigate the surface morphology of the studied compositions. The average grain size of the composites has reduced slightly with the enhancement of ferrite part up to 20% and after that it has increased again. The real part of the initial permeability (μ i ′) was found to be increasing with ferrite content. The real part of dielectric constant (ε ′) exhibits dispersion at low-frequency region because of Maxwell–Wagner type interfacial polarization. The complex impedance spectroscopy has been used to separate the grain and grain boundary contribution to the total resistance. Existence of the hopping conduction mechanism has been confirmed through the study of electric modulus. The hysteresis loops of the compositions are studied to confirm the response of ferrite part to the applied magnetic field. The magnetoelectric voltage coefficients of the composites have reduced with the ferrite part. The maximum magnetoelectric voltage coefficient is nearly 158 × 103 Vm−1 T−1 for the 0.1LNMFO–0.9BDFO composite, which is about three times of the reported value compared to other composites. [ABSTRACT FROM AUTHOR]

In this research, the causal relationship between the dielectric properties and the structural characteristics of 0.5 & 1.0 mole % Ta2O5 doped BaTiO3 based ceramic materials were investigated under different sintering conditions. Dielectric properties and microstructure of BaTio3 ceramics were significantly influenced by the addition of a small amount of Ta2O5. Dielectric properties were investigated by measuring the dielectric constant (k) as a function of temperature and frequency. Percent theoretical density (%TD) above 90 % was achieved for 0.5 and 1.0 mole %Ta2O5 doped BaTiO3. It was observed that the grain size decreased markedly above a doping concentration of 0.5 mole % Ta2O5. Although fine grain size down to 200 - 300 nm was attained, grain sizes in the range of 1-1.8µm showed the most alluring properties. The fine-grain quality and high density of the Ta2O5 doped BaTiO3 ceramic resulted in tenfold increase of dielectric constant. Stable value of dielectric constant as high as 13000 - 14000 was found in the temperature range of 55 to 80 °C, for 1.0 mole % Ta2O5 doped samples with corresponding shift of Curie point to ∼82 °C. Experiments divulged that incorporation of a proper content of Ta2O5 in BaTiO3 could control the grain growth, shift the Curie temperature and hence significantly improve the dielectric property of the BaTiO3 ceramics. [ABSTRACT FROM AUTHOR]

Multiferroic composites (1– y )BiFeO 3 – y Ni 0.50 Cu 0.05 Zn 0.45 Fe 2 O 4 ( y =0.0, 0.1, 0.2, 0.3 and 0.4) are synthesized by the standard solid state reaction method. The X-ray diffraction analysis affirms the formation of both the component phases and also reveals that there is no chemical reaction between them. From the energy-dispersive X-ray spectroscopy study it is observed that the percentage of the elements in the component phases is well consistent with the nominal composition of the composites. Field Emission Scanning Electron Microscopy analysis shows almost homogeneous mixture of the two phases. The real part of the initial permeability increases (up to 67%) and the loss decreases with the ferrite content in the composites which is important in application point of view. Dielectric constant (ε′), loss tangent and AC conductivity are measured as a function of frequency at room temperature. The highest ε′ is obtained for 0.6BiFeO 3 –0.4Ni 0.50 Cu 0.05 Zn 0.45 Fe 2 O 4 composite. The dielectric dispersion at lower frequency (<10 5 Hz) is due to the interfacial polarization. The complex impedance spectroscopy is used to correlate between the electrical properties of the studied samples with their microstructures. Two semicircular arcs corresponding to both grain and grain boundary contribution to electrical properties have been observed in all the studied samples. The maximum magnetoelectric voltage coefficient is found to be ∼38 mV cm −1 Oe −1 for the composite with 80% ferroelectric+20% ferrite phases. The present composite might be a promising candidate as multiferroic materials showing effective electric and magnetic properties. [ABSTRACT FROM AUTHOR]

• LNMFO – BYFO composites show the coexistence of ferroelectric and ferromagnetic phases. • The variation of μ i ' with frequency is almost stable for all composites. • Both modulus and conductivity exhibit polaron hopping type of conduction. • Cole-Cole plots show the dominating behavior of grain. • The α ME is quite high (~182 × 103Vm−1T−1) for the 0.1NZFO – 0.9BYFO composite. The room temperature magnetoelectric coupling was elucidated by the analysis of structural, magnetic, and electrical properties of x Li 0.1 Ni 0.2 Mn 0.6 Fe 2.1 O 4 – (1- x)Bi 0.8 Y 0.2 FeO 3 composites. The X-ray diffraction pattern shows that the ferromagnetic phase forms a cubic spinel structure and the ferroelectric phase forms a rhombohedral perovskite structure. The density of the composites decreases with ferrite content. The average grain size slightly decreases with ferrite content for x = 0.1 and increases for further increasing ferrite content. The real part of initial permeability and saturation magnetization increase with increasing ferrite content. The real part of the dielectric constant decreases rapidly with the increase of frequency showing dielectric dispersion at lower frequencies and then remains almost constant at higher frequencies. The dielectric loss of the samples reduces with the increase of the ferrite phase. The ac conductivity of composites increases with frequency, indicating that the conduction is due to small polaron hopping. The study of impedance spectroscopy suggests that grain contribution is effective for the conduction mechanism in the composite. The maximum magnetoelectric voltage coefficient is observed (~182 × 103Vm−1T−1) for the 0.1LNMFO – 0.9BYFO composite which is useful for fabricating magnetic sensors. [ABSTRACT FROM AUTHOR]