Fine-grained magnetoelectric Sr0.5Ba0.5Nb2O6 -CoFe2O4 composites synthesized by a straightforward one-pot method (original) (raw)
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J.Mater. Chem. C, 4 (2016) 4792, 2016
Magnetoelectric composites (CoFe2O4)x –(BaTiO3)1-x with x = 0.1, 0.2, 0.3, 0.4 and 0.5 were prepared by a polyol mediated synthesis route. The densification step was performed in a reducing forming gas atmosphere at 1250 °C. Under these conditions Co 2+ and Fe 3+ are reduced to the corresponding metals and thus a reaction of these elements with the BaTiO3 matrix is prevented. Reoxidation in air to CoFe2O4 at a rather low temperature of 800 °C leads to samples free of secondary phases. While the course of the synthesis was monitored by TGA, XRD and photometric analysis, the final composites were characterized via SEM, EDX, impedance spectroscopy and magnetic and magnetoelectric (ME) measurements. All samples show pronounced ME hystereses and a ME maxima dependent on the H dc field sweep direction. The sample with x = 0.4 exhibits the highest maximum a ME of 420 mV Oe -1 cm -1 .
Ceramics International 45 (2019) 23013–23021, 2019
Multiferroic particulate composites have been fabricated by taking the morphotropic phase boundary composition of ferroelectric phase Bi(Ni 1/2 Ti 1/2)O 3-PbTiO 3 and magnetic phase (Ni,Zn)Fe 2 O 4. The ferroelectric phase has coexisting monoclinic and tetragonal perovskite structures with space group Pm and P4mm, respectively whereas the magnetic phase has spinel cubic structure with space group Fd3 ‾m. Rietveld structural analysis for the each components of composite reveals that the tetragonality (c/a) of the ferroelectric phase continuously increases with increasing the concentration of magnetic phase and finally transform in rhombohedral (R3 ‾c) phase suggesting partial ionic diffusion between ferroelectric and magnetic phases. Composition dependent Mössbauer spectra of (1-x)Bi(Ni 1/2 Ti 1/2)O 3-PbTiO 3 /x(Ni,Zn)Fe 2 O 4 reveals the superparamagnetic like behavior for the ferroelectric rich composition with x = 0.2. The magnetic ordering increases for the composition with x = 0.4 and 0.6 which completely transforms into ferrimagnetic for the composition with x = 0.9. Unlike the ferroelectric or magnetic components that do not exhibit the magnetoelectric response separately, significant value of magnetoelectric coefficient (> 30 mV/
Dalton transactions (Cambridge, England : 2003), 2014
Lead-free particulate multiferroic composites of [0.94(Na0.5Bi0.5)TiO3-0.06 BaTiO3]:(Co0.6Zn0.4)(Fe1.7Mn0.3)O4 were synthesized and magnetoelectric (ME) properties were studied. X-ray diffraction and microstructural studies indicated the formation of a two-phase composite system without any impurities. The shift of Raman modes corresponding to ferroelectric and ferrite phases was assigned to the induced strain amid the formation of a two-phase system, in relation to the fraction of each phase in the samples. A strong local piezoresponse and hysteresis loops observed for composites established the ferroelectric properties at a nanoscale. Magnetostriction measurements revealed values of λ11 = -10.4 and λ12 = 5.3 ppm and piezomagnetic coefficient dλ11/dH = -0.0087 ppm Oe(-1) at 0.45 kOe for a composite with a ferrite concentration of 35 mol%. A maximum change of 18.5% in magnetization after electrical poling indicates a strong magnetoelectric response of the present composites followed...