Large magnetoelectric coefficient in Co-fired Pb (Zr0.52Ti0.48)O3–Pb (Zn1/3Nb2/3)O3–Ni0.6Cu0.2Zn0.2Fe2O4 trilayer magnetoelectric composites

Abstract

Magnetoelectric materials possess coupling between the ferroic properties polarization, and magnetization [1–4]. The interrelation between ferroelectricity and magnetization allows the magnetic control of ferroelectric properties and vice versa. Single phase magnetoelectric (ME) materials (such as Cr2O3, BiFeO3, YMnO3, etc.) suffer from the drawback that ME effect is weak [5–7]. Better alternatives are ME composites that have higher magnitudes of the ME voltage coefficient exploiting the product property of the materials [8–10]. Magnetoelectric (ME) effect in a particulate sintered composite was obtained by combining magnetostrictive and piezoelectric phases [11–15]. Sintered composites have many advantages, such as simplicity in synthesis, cost-effective materials and fabrication process, and better control of desired geometry. However, the ME response is low of the order of 100 mV/cm Oe. Recently, laminated magnetoelectric (ME) composites synthesized by using giant piezoelectric and magnetostrictive materials have gained attention because they exhibit superior ME response [16–19]. Dong et al. [20] have reported a composite where piezofiber is laminated between the high permeability magnetostrictive FeBSiC alloy using epoxy and found a large response of 22 V/cm Oe at 1 Hz. The research on sintered composites has shown that corfiring multiple layers can provide higher ME coefficients. However, the drawback is that tape-casting process for synthesizing multilayers of heterogeneous materials is complex. Further, in order to improve the property of the sintered ME composites, the other variables such as composition, microstructure, geometry, texture, and post sinter heat treatment needs to be optimized. In our previous studies, it has been shown that soft piezoelectric phase (high dielectric and piezoelectric constant), soft magnetic phase (high permeability and low coercivity) [21], large piezoelectric grain size ([1 lm) [22], layered structure (bilayer/trilayer) [23] and post-sintering thermal treatment (annealing and aging) [24] improve the magnetoelectric property. In order to combine all the parameters together, the challenge is to develop a unique fabrication process, in which layers of piezoelectric and magnetostrictive can be cofired together. Moreover the poling process of the piezoelectric phase requires high resistivity, and thus electrodes have to be preserved during sintering. We found that pressure assisted sintering can produce trilayer composites with any desired dimensions. Further, we designed the compositions such that sintering could be done at low temperatures of 900 C which results in stable electrodes. The objective of this letter is to analyze the microstructural, piezoelectric, dielectric, and magnetoelectric properties of this trilayer sintered ME composite.