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In the present study, we report a significant magnetoelectric coupling in lead-free (1-x)Ba0.95Ca0.05Ti0.95Sn0.05O3 - (x)Ni0.7Zn0.3Fe2O4 (x = 0.10, 0.15, 0.20, 0.25 and 0.30) particulate composites prepared by solid-state route. Phase purity and crystal structure of the composites were examined by the X-ray diffraction measurement. With the incorporation of the magnetic NZFO phase, a decrease in the tetragonality of the ferroelectric BTCS lattice was confirmed by the full pattern match of the XRD data using Rietveld analysis. FESEM micrographs revealed improved microstructures with the addition of ferrite concentrations in the composites. Simultaneous presence of ferroic orders in the composites was confirmed from the room-temperature P-E and M-H hysteresis loops. Direct magnetoelectric voltage measurement of the composites established the strain-mediated coupling between the BTCS and NZFO phases. Highest RT first-order magnetoelectric voltage coefficient (α/d = 6.24 mV/cm-Oe) of the x = 0.25 composite is attributed to better individual ferroic properties and improved microstructure of this sample. [ABSTRACT FROM AUTHOR]

In this work, effect of sintering temperature on magnetoelectric properties of lead-free [85 wt% Ba0.95Ca0.05Ti0.95Sn0.05O3 (BTCS)–15 wt% Ni0.7Zn0.3Fe2O4 (NZFO)] particulate composite has been studied. The composites were synthesized by solid-state reaction method and sintered at five different temperatures. Structure analysis of constituent phases of the composites has been examined by X-ray diffraction (XRD) technique. Rietveld refinement confirmed that the piezoelectric BTCS comprised two phases (tetragonal and orthorhombic) and inverse spinal NZFO has a cubic phase in the composites. Surface morphology study carried out by Field Emission Scanning Electron Microscope (FESEM) accounted the increase in uniform grain size and connectivity of the constituent phases with the increase of sintering temperature. Dielectric constant vs. temperature (Ɛr–T) graph showed two anomalies corresponding to the ferroelectric transition temperature of BTCS and the magnetic transition temperature of NZFO phase. Enhancement in saturation polarization (PS) and decrease in saturation magnetization (MS) at room temperature were observed with the increase of sintering temperature. The composite, sintered at 1300 °C for 4 h showed maximum change in magnetodielectric value (MD% ∼ 1.94 at 100 kHz frequency) at room temperature. This sample also exhibited the highest first and second order magnetoelectric coefficients (α/d = 2.37 mV/cm-Oe and β/d = 40.69 µV/cm-Oe2) at room temperature which was explained on the basis of sintering temperature-dependent ferroic properties of the individual phases. [ABSTRACT FROM AUTHOR]

In the present investigation, we report a comparative study of structural, magnetic and electric transport properties in bulk NiFe 2 O 4 and Ni 0.7 Zn 0.3 Fe 2 O 4 ceramics. The materials were synthesized by solid state reaction method. X-ray diffraction analysis confirmed the cubic spinel structure of the ferrite samples belonging to the Fd 3 ‾ m space group. The structural analysis of the ceramics was comprehensively evaluated from Rietveld refinements of the XRD data and Raman studies. An increased grain size in the Ni 0.7 Zn 0.3 Fe 2 O 4 microstructure was noticed due to Zn substitution. Both structural and microstructural modifications led to a significant change in the magnetic and electric properties of the Ni 0.7 Zn 0.3 Fe 2 O 4 ceramic. A large increase in saturation magnetization with decreased coercivity was noticed in the Ni 0.7 Zn 0.3 Fe 2 O 4 system due to Zn substitution. DC resistivity was observed to decrease in the Zn-substituted nickel ferrite ceramic due to increased grain size and larger electron hopping between Fe3+ and Fe2+ ions, as verified by the XPS analysis. Further, a remarkable dielectric relaxation has been observed in the Ni-Zn ferrite owing to greater charge hopping and interfacial polarization. Complex impedance spectra of Ni 0.7 Zn 0.3 Fe 2 O 4 revealed evidence of surface polarization contribution with grain and grain boundary effect on the electric transport properties. [ABSTRACT FROM AUTHOR]

In this report, we present the structural, electrical, and optical study of layer-structured SrBiTiO (SBT) ceramic prepared by solid-state reaction route. The X-ray diffraction and Rietveld refinement studies show a single-phase orthorhombic structure with space group Aam. The scanning electron micrograph shows plate-like grains. The various Raman peaks originated due to the TiO octahedron confirm the orthorhombic structure. The temperature-dependent dielectric study shows a normal ferroelectric phase transition with a transition temperature at 813 K (540 °C). Impedance studies show a non-Debye-type relaxation and relaxation frequency shift to higher side with increase in temperature. The Nyquist plot shows overlapping semicircles which results the existence of both for grain and grain boundary effect in SBT ceramic. The frequency-dependent AC conductivity at different temperatures indicates that the conduction process is thermally activated and the spectra follow the universal power law. The variation of DC conductivity confirms that the SBT ceramic exhibits negative temperature coefficient of resistance behavior. The Ferroelectric behavior is studied by hysteresis loop. The optical band gap is found to be 2.93 eV from the UV-Visible spectroscopy study. The room-temperature photoluminescence study shows a strong red emission. [ABSTRACT FROM AUTHOR]

In the present study, we investigated the structural, dielectric and piezoelectric properties of lead-free polycrystalline BaTiO 3 (BT) and Ba 0.95 Ca 0.05 Ti 0.95 Sn 0.05 O 3 (BTCS) ceramics. The ceramics were synthesized using the conventional solid-state reaction route. Rietveld analysis confirmed a tetragonal symmetry (space group P4mm) in BT ceramic, and a double-phase coexistence of tetragonal and orthorhombic (space group Amm2) symmetry in BTCS ceramic at room temperature. The dielectric study revealed a decrease in the Curie temperature (T C) from 114 °C to 72 °C and an increase in the orthorhombic-tetragonal (T OT) phase transition temperature from 9 °C to 27 °C in comparison to the same structural transitions of BT system. Further, the BTCS ceramic exhibited a relaxor ferroelectric behavior with frequency dispersion and diffused phase transitions. Due to the T-O phase coexistence, significant enhancements in the dielectric and piezoelectric properties were observed in the BTCS ceramic at room temperature, with a giant RT dielectric constant (Ɛ r) ∼ 4380 at 1.5 kHz frequency, piezoelectric coefficient (d 33) ∼ 431 pC/N, electrostrain (S) ∼ 0.142%, and converse piezoelectric coefficient (d 33 *) ∼ 403 pm/V. • Effect of Ca and Sn modification in BT system on structural, dielectric and piezoelectric properties. • Coexistence of RT tetragonal and orthorhombic symmetry in BTCS ceramics. • Decrease of T C from 114 °C to 72 °C, and increase in T O-T transition temperature from 9 °C to 27 °C. • RT relaxor ferroelectric nature of BTCS ceramics. • RT giant Ɛ r ∼ 4380 at 1.5 kHz, d 33 ∼ 431 pC/N, electrostrain (S) ∼ 0.142% make BTCS ceramic useful for device applications. [ABSTRACT FROM AUTHOR]