Junyi Zhai

A three-phase magnetoelectric composite of piezoelectric ceramics, rare-earth iron alloys, and polymer

A class of multiferroic, three-phase particulate composites of Tb–Dy–Fe alloy, lead–zirconate–titanate (PZT), and polymer are investigated, in which a small volume fraction f of Tb–Dy–Fe alloy particles are dispersed in a PZT/polymer mixture. The measured dielectric, piezoelectric, and magnetoelectric properties demonstrate that a percolation transition occurs at f∼0.12 in the composites. When f is low (e.g., f<0.07), the composites exhibit piezoelectric and increasing magnetoelectric response. In the critical f range of 0.07<f<0.12, such piezo- and magnetoelectric responses sharply drop, and equal zero at the percolation threshold, above which the composite becomes a conductor and a magnetostrictive composite only.

Magnetic-dielectric properties of NiFe2O4/PZT particulate composites

Particulate composites of lead–zirconate–titanate (PZT) and NiFe2O4 were prepared using conventional ceramic processing. The measured magnetoelectric (ME) response demonstrated strong dependence on the volume fraction of NiFe2O4, the magnetic field, and the angle between the magnetic field and polarization in the ceramics. A large ME voltage coefficient of about 80 mV cm−1 Oe−1 was observed for 0.32NiFe2O4/0.68PZT composite ceramic. In particular, at low magnetic fields, the ceramics were found to have a large ME response, linearly varying with both dc and ac magnetic fields.

Coupled magnetodielectric properties of laminated PbZr0.53Ti0.47O3/NiFe2O4 ceramics

Simple multiferroic laminated ceramics of lead–zirconate–titanate PbZr0.53Ti0.47O3(PZT)/NiFe2O4 were prepared by a conventional ceramic processing. The measured magnetodielectric properties demonstrated strong dependence on the relative thickness of the PZT layers, magnetic bias, and angle between the bias and polarization in the laminated ceramics. Recent theoretical approaches were employed to explain these observed behaviors. The maximum magnetoelectric sensitivity (αE31) of the ceramics samples could reach up to as high as 0.21 V/A at 11.9 kA/m. In particular, at low magnetic bias, the laminated ceramics were found to have a very large magnetoelectric sensitivity linearly varying with the bias.

Large high-frequency magnetoelectric response in laminated composites of piezoelectric ceramics, rare-earth iron alloys and polymer

Multiferroic laminated composites consisting of lead-zirconate titanate (PZT)/polyvinylidene-fluoride (PVDF) and Tb–Dy–Fe alloy (Terfenol-D)/PVDF particulate composite layers, prepared by a simple hot-molding technique, are reported. In the laminated composites, the polymer PVDF is used just as a matrix binder. Our results demonstrate that the three-phase laminated composites exhibit remarkable magnetoelectric response especially at high frequency where an electromechanical resonance appears. The maximum magnetoelectric sensitivity of the laminated composites is as high as over 3000 mV/cm Oe at the resonance frequency of around 100 kHz.

Coupled magnetic–electric properties and critical behavior in multiferroic particulate composites

We report on a systematic experimental investigation of a class of multiferroic, three-phase particulate composite of Tb–Dy–Fe alloy, lead–zirconate–titanate (PZT), and polymer, in which a small volume fraction f of Tb–Dy–Fe alloy particles without and with the particle surfaces modified by an inactive surfactant are dispersed in PZT/polymer mixture. The measured electrical properties demonstrate that a percolation transition occurs in the three-phase composite as in normal two-phase metal–insulator continuum media. Our piezoelectric measurements also show a percolation transition which provides an experimental test of the critical behavior of the piezoelectric composites with conductive fillers in the percolation regime. Accordingly, the multiferroic composite exhibits increasing magnetoelectric response in the low f range, but such magnetoelectric response sharply drops when f approaches the percolation threshold above which the composite becomes a conductive, magnetostrictive composite only. The inacti...

The magnetoelectric properties of lead zirconate titanate/terfenol-D/PVDF laminate composites

Abstract Lead zirconate titanate (PZT-5)/Tb0.28Dy0.72Fe1.95 (Terfenol-D)/poly vinylidene fluoride (PVDF) laminate composites were prepared using stacking and heat-pressing together one Terfenol-D+PVDF disk and two layers of PZT+PVDF. The dependence of the magnetoelectric conversion coefficient (dE/dH) of these composites on the value of applied dc magnetic field, thickness of layers and frequency of the ac magnetic field has been studied systematically. The results indicate that the dE/dH can reach the maximum 126.84 mV/cm.Oe when the layers thickness ratio of PZT+PVDF to Terfenol-D+PVDF is 0.375/1.0.