Lead-free Magnetoelectric Composites Research Articles

Synthesis and structural studies of lead-free (Na0.5Bi0.5)0.92Ba0.08TiO3 - Co0.6Zn0.4Fe1.7Mn0.3O4 magnetoelectric composites

Two phase Lead-free magnetoelectric composites with the formula (1-x) (Na0.5Bi0.5)0.92Ba0.08TiO3-(x) Co0.6Zn0.4Fe1.7Mn0.3O4 [(1-x) NBBT-xCZFMO] (where x = 0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1 mol%) have been synthesized through conventional solid-state reaction method. X-ray diffraction (XRD) and Scanning electron microscopy (SEM) methods have been employed for structural and morphology studies on the synthesized samples. XRD and SEM studies revealed that the single-phase synthesis of NBBT & CZFMO and the existence of both the parent phases in the composites. Here, ferroelectric NBBT formed in tetragonal crystal structure with P4bm space group, whereas ferrite CZFMO crystallized in Cubic structure with Fd-3m space group. Raman spectroscopy is also carried out on all the synthesized samples. In case of NBBT six Raman active modes are observed between wave numbers from 100 cm−1 to 1000 cm−1 and in accord with the earlier reports. Whereas, when it comes to CZFMO, five modes are observed in the region of 100 cm−1 to 1000 cm−1 at 162 cm−1, 309 cm−1, 472 cm−1, 620 cm−1 and 690 cm−1. The composites contain the Raman peaks of both NBBT and CZFMO. The shifting of the Raman peaks observed in the composites indicates the presence of strain at the interface of NBBT and CZFMO phases. The results are discussed in detail.

Evolution of microstructure and properties in BT-based lead-free magnetoelectric composite

Owing to the excellent conversion properties between magnetic and electric properties, magnetoelectric composites have been widely used in devices. With the growing concerns about the environment, developing environmentally friendly lead-free magnetoelectric composites with high performance are very important. Here, (1-x)0.82Ba(Ti0.89Sn0.11)O3-0.18(Ba0.7Ca0.3)TiO3-xCoFe2O4 [(1-x)BTS-BCT-xCFO] magnetoelectric composites are synthesized by solid-state method, and the effect of CFO on the microstructure and magnetoelectric properties is systematically studied. The perovskite type piezoelectric phase and spinel structured piezomagnetic phase in diffraction patterns are independent of each other. Due to the inhibiting effect of CFO on grain size for BTS-BCT, the grain size of magnetoelectric composites is dominated by CFO. The electric properties deteriorate, and magnetic properties increase with increasing CFO. Meanwhile, the optimal ME coefficients (αE31∼8.12 mV/cm∙Oe and αE33∼7.84 mV/cm∙Oe) are obtained in the (1-x)BTS-BCT-xCFO with x = 0.20, which are superior or comparable to that of some lead-based and lead-free magnetoelectric composites. Therefore, (1-x)BTS-BCT-xCFO material systems have a promising prospect in application.

Structural, magnetic, magneto-dielectric and magneto-electric properties of (1-x) Ba0.85Ca0.15Ti0.90Zr0.10O3 – (x) CoFe2O4 lead-free multiferroic composites sintered at higher temperature

Here in this article synthesis of lead-free magnetoelectric composites (1-x) Ba0.85Ca0.15 Ti0.9Zr0.1)O3 - xCoFe2O3 (BCTZ-CFO, x = 0.4, 0.5, and 0.6) is reported. Structural, magnetic, dielectric, magnetodielectric and magnetoelectric properties of lead-free BCTZ-CFO composites sintered at higher sintering temperature have been systematically investigated. The piezoelectric (ferroelectric) phase has been synthesized using the sol–gel route, while Metallo-organic decomposition (MOD) route was employed to prepare piezomagnetic (ferrite) phase. The structural and microstructural properties were studied using X-Ray diffraction and Scanning electron Microscope respectively acknowledged the presence of two distinct phases as ferrite and ferroelectric in composite samples. The dense microstructure and larger average grain size were observed for samples with higher ferrite phase content. Long-range magnetic order was observed under magnetic study for all-composites. The magnetic properties enhanced for composites prepared with higher ferrite phase content. Dielectric properties were studied at room temperature and enhanced dielectric constant has been observed for samples with higher ferroelectric phase content, while minimum dielectric loss was observed for sample with 50/50 ferrite/ferroelectric phase composition. The magnetodielectric response has been also investigated for all ME composites. Leakage current characterization has been also discussed at and above the room temperature. The magneto-electric coupling response was measured of all composites. The higher value of magneto-electric coupling coefficient has been observed for 0.5BCTZ-0.5CFO composite due to maximum possible ferrite-ferroelectric hetero-structure phase contact area.

Investigation of structural, dielectric, and magnetoelectric properties of K0.5Na0.5NbO3–MnFe2O4 lead free composite system

In the present work, lead-free magnetoelectric composites (1 ̶x)K0.5Na0.5NbO3–(x)MnFe2O4 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) synthesized by solid-state reaction route have been studied for their structural, dielectric, and magnetoelectric properties. The micro-structural analysis (XRD, FESEM, EDX, FTIR, and RAMAN spectroscopy) indicates the coexistence of diphase in the composites. Compared to the individual phases, composites exhibit better electrical properties such as low leakage current, high resistivity, high dielectric constant, and low dielectric loss. I–V characteristics reveal that the conduction behavior of the composites is ohmic in nature in whole tested electric field range at room temperature. The maximum value of dielectric constant is noticed for composite with 20 wt% of MnFe2O4 among the composites. The complex modulus analysis reveals the presence of non-Debye type phenomenon with spreading of relaxation time in the composites. Nyquist plots reveal that the composites exhibit polydispersive Maxwell–Wagner relaxation. The magnetic measurements indicate that the magnetic behavior of the composites lies on the mass content of MnFe2O4 phase. The magnetization increases with MnFe2O4 weight percentage which provides information regarding the magnetoelectric effect (ME) coupling between the magnetostrictive ferromagnetic and ferroelectric phases. Furthermore, ME effect is evaluated as a function of applied magnetic field. The highest ME response of 2.02 mV/cm-Oe is observed for composite with 80 wt% content of MnFe2O4. Findings of this research make these composites worthy material for environment-friendly ME device applications.

Investigation of magnetoelectric effect in lead free K0.5Na0.5NbO3-BaFe12O19 novel composite system

Lead-free magnetoelectric composites (1−x)K0.5Na0.5NbO3—(x)BaFe12O19 (x = 30, 40, and 50 wt%) are synthesized using solid state reaction method. X-ray diffraction (XRD) patterns confirm formation of diphase composites. Field emission scanning electron microscopy (FE-SEM) gives information about grain size, connectivity, and microstructure of constituent phases. Dielectric parameters of composite samples are studied as a function of temperature and the transition temperatures corresponding to both the constituent phases are observed in the composite samples. Dielectric constant has been found to decrease with addition of ferrite. Room temperature multiferroic behaviour has been confirmed using P-E and M-H hysteresis loops and magnetoelectric measurement. Polarization is found to decrease; however, magnetization increases with ferrite weight percentage. The highest αME of 4.08 mV/(cm·Oe) is obtained for x = 30 wt% composite and it is realized that ferrite content significantly affects magnetoelectric behaviour.

Electrical properties of conventional and microwave sintered lead free magnetoelectric composites

Here we report comparison of dielectric properties of composition synthesized by microwave and conventional sintering. Microwave sintering requires less time and temperature to achieve the same quality of materials as sintered by conventional route. The material sample was prepared by conventional solid state method and sintered in conventional & microwave furnace. Sintered samples were then subjected to XRD analysis. X-ray diffraction revealed the formation of single phase material. The dielectric and ferroelectric properties were recorded for both the samples and properties were found to improve in microwave sintered samples. There is also a significant improvement in density by microwave processing.

Enhanced magnetoelectric effect in Metglas/K0.5 Na0.5NbO3/metglas lead-free ME laminates

We report the magnetoelectric (ME) coupling in lead-free ME composites composed of Metglas (2605SA1) and K[Formula: see text]Na[Formula: see text]NbO3 (KNN) phases. Thickness of the magnetostrictive layers ([Formula: see text] is changed by stacking number of Metglas layers ([Formula: see text]25[Formula: see text][Formula: see text]m for each layer) while KNN is maintained at a fixed thickness ([Formula: see text]300[Formula: see text][Formula: see text]m). As the number of Metglas layers increased, the peak magnitude of [Formula: see text] first increases, reaches a maximum and then decreases afterward. The static magnetic field ([Formula: see text], where [Formula: see text] shows maximum magnitude shift toward a higher value as number of layers increases. The maximum value of [Formula: see text] 91[Formula: see text]mVcm[Formula: see text]Oe[Formula: see text] is observed for optimized thickness ratio of [Formula: see text]/[Formula: see text] 1 (i.e. [Formula: see text] 5 layers) at [Formula: see text] 160[Formula: see text]Oe. The [Formula: see text] is further enhanced by taking advantage of magnetic flux concentration effect of Metglas as a function of its sheet aspect ratio. The present composites can offer promising opportunities of engineering environmental friendly ME laminate for applications in ME devices such as energy harvester and magnetic field sensors.

Magnetoelectric effect in lead free piezoelectric Bi1/2Na1/2TiO3–modified CFO based magnetostrictive (Co0.6Zn0.4Fe1.7 Mn0.3O4) particulate nanocomposite prepared by sol-gel method

Lead free magnetoelectric composites that comprise Co0.6Zn0.4Fe1.7Mn0.3O4 (CZFMO) and Bi1/2Na1/2TiO3 (BNT) were synthesized using sol-gel method and it's structural, dielectric, magnetic, ferroelectric and magnetoelectric (ME) properties were studied. The X-ray diffraction displayed the single phase formation of parent phases and the presence of two phases in the composites. The temperature dependent dielectric spectra of samples indicates two anomalies at ~220°C and ~320°C were ascribed to ferroelectric to antiferroelectric, and anti-ferroelectric to paraelectric phase transitions respectively. Room temperature (RT) magnetic measurements show that composites are soft magnetic. The composite with x=0.2, showed the large value of ME voltage coefficient (αE)~58mV/cmOe. Moreover, these ME composites provide a great opportunity as potential lead free systems for multifunctional devices.

MULTIFERROISM AND MAGNETOELECTRIC COUPLING IN NANO-MICROSCALE LEAD-FREE COMPOSITE BY 0.3Co-FERRITE AND 0.7(K0.5Na0.5)NbO3-BASED FERROELECTRIC MATRIX

Nontoxic lead-free multiferroic composites are synthesized by incorporating the dispersed 0.3 CoFe 2 O 4 (CFO) ferromagnetic nanoparticles into 0.7( K 0.5 Na 0.5) NbO 3- LiSbO 3 (KNN-LS5.2) ferroelectric micromatrix. The multiferroicity of the composite can be verified by polarization-electric field hysteresis loop and magnetic hysteresis loop. The composite exhibits excellent magnetic properties. A dilution effect is observed in magnetic hysteresis loops. The field dependence of ME voltage coefficient is given as a function of magnetic field from -4 kOe to 4 kOe with a maximum magnetoelectric voltage coefficient of 10.7 mV ⋅ cm -1⋅ Oe -1 at the frequency of 1 kHz. It is a very high value in the lead-free magnetoelectric composites system for the potential use on multifunctional devices.

Dielectric and Magnetoelectric Properties of Nano-Microscale Lead-Free Composite by 0.4Co-Ferrite and 0.6(K<sub>0.5</sub>Na<sub>0.5</sub>)NbO<sub>3</sub>-Based Ferroelectric Matrix

Lead-free multiferroic magnetoelectric composites were prepared by incorporating the dispersed 0.4CoFe2O4ferromagnetic nanoparticles into 0.6(K0.5Na0.5)NbO3-LiSbO3ferroelectric micromatrix. From the x-ray diffraction analysis, it was observed that almost no chemical reaction occurs between the ferrite and the ferroelectric materials used to form the composite. Dielectric properties as a function of frequency were measured. The magnetoelectric couple effect was given as a function of magnetic field with a maximum magnetoelectric voltage coefficient of 15.01mV·cm-1·Oe-1at 1kHz, which was a very high value in the lead-free magnetoelectric composites system for the potential use on actuators and sensors, etc.