Characterization Of Magneto-electromechanical Behaviors Of BNT/NFO Bilayer Films By Bulge Technique

Multiferroic magnetoelectric(ME) composites are attractive materials for various electrically and magnetically cross-coupled devices. Many studies have been conducted on fundamental understanding, fabrication processes, and applications of ME composite material systems in the last four decades which has brought the technology closer to realization in storage, sensors, drives, and other real devices. As magnetoelectric devices have been used more widely, their properties may be affected by magnetic field, electric field or even more than one at the same time in complex service environment. Therefore, it is important to master their performance change and failure mechanism in complex service environments. In this paper, ferroelectric material Bi3.15Nd0.85Ti3O12(BNT) and magnetic NiFe2O4(NFO) were chosen as the research objects, the mechanical-electromagnetic properties of BNT, NFO and BNT/NFO were tested and analyzed on the novel multifunctional bulge test system. The main contents are summarized as follows:Firstly, the variations of elastic modulus and ferroelectric properties of BNT films were studied under different electric field and oil pressure. The results are as follows, the residual stress and elastic modulus of BNT films were 215.9 MPa and 158.8 GPa by bulge test. The elastic modulus of BNT films decreased from 158.8 GPa to 58.5 GPa with the electric field increased from 0 kV/cm to 400 kV/cm. The remnant polarization and coercive field of BNT thin films increased 34.7% and 34.1% with the bulge oil pressure increased, separately.Secondly, the impact of ferroelectric properties and ferromagnetic properties of NFO films were studied under different magnetic field and oil pressure. The results show that: the residual stress and elastic modulus of NFO films were 500.8 MPa and 187.8 GPa by bulge test. The elastic modulus of NFO film increased to 484.6 GPa and magnetostriction coefficient increased from -63.5 ppm to -187.5 ppm with the magnetic field increased from 0 Oe to 800 Oe. The remnant magnetization and coercive field of NFO thin films decreased 75% and 44% with the bulge oil pressure increased, respectively.Thirdly, the impact of ferroelectric properties and different magnetic field and oil pressure of BNT/NFO films were studied. The saturated polarization and coercive field reduced from 13.9 ?C/cm2 and 160.6 kV/cm to 12.8 ?C/cm2 and 146.0 kV/cm with the magnetic field increased from 50 Oe to 800 Oe. When the bulge oil pressure increased from 0 kPa to 15 kPa, saturated magnetization signal and coercive field decreased from 3.24 mV and 934.5 Oe to 1.40 mV and 549.8 Oe, decreased 56.8% and 41%, respectively.Fourthly,the variations of elastic modulus of BNT/NFO films were studied under different electric field, magnetic field and magnetoelectric coupling field. The results are as follows, the elastic modulus and residual stress of BNT/NFO films were 123.3 GPa and 43,2 MPa by bulge test in the initial state. The elastic modulus of BNT/NFO films decreased and increased with electric field increased and electric field increased, separately. It is interesting that, the elastic modulus increases first and then decreases under the increasing electric field in the 800 Oe constant magnetic field. The elastic modulus decreases first and then increases under different magnetic field in the 300 kV/cm cornstant electric field.