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Influence of ferroelectric-electrode interfaces on the electrical properties of BaTiO3-CoFe2O4 magnetoelectric composites L. B. Hao • D. X. Zhou • S. P. Gong • Q. Y. Fu • W. Luo • G. Jian • F. Xue • L. Zhou

Received: 18 September 2012 / Accepted: 19 January 2013 / Published online: 22 February 2013 Ó Springer Science+Business Media New York 2013

Abstract In order to further investigate the influence of electrode types and preparation conditions on the electrical properties of magnetoelectric (ME) composite ceramics, layered BaTiO3-CoFe2O4 (BTO–CFO) composites were prepared using tape casting method, and the effects of silver and aluminium electrodes on the electrical properties were studied. It is found that the different electrical properties of the ME composites are related to the ferroelectricsilver and ferroelectric-aluminium interfaces formed at the same annealing temperature, in which the former enhance the leakage current density, dielectric properties and AC conductivity, but lower the ferroelectric properties compared to the latter. Meanwhile, the electrical properties of the composite, especially leakage current and ferroelectric properties, are influenced by the silver electrode annealing temperature. In addition, space charges and polarons are responsible for the dielectric constant and AC conductivity of the ME composites, respectively.

1 Introduction A new class of devices, such as transformers [1], sensors [2, 3] and bidirectional current–voltage converters [4],

L. B. Hao  D. X. Zhou  S. P. Gong  Q. Y. Fu (&)  W. Luo  F. Xue  L. Zhou Department of Electronic Science and Technology, Huazhong University of Science and Technology, Wuhan 430 074, People’s Republic of China e-mail: [email protected] G. Jian School of Materials Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang, People’s Republic of China

have been designed. These devices are on the basis of magnetoelectric (ME) effect, which is induced by the interaction between electrical and magnetic fields in ME materials [1, 2, 5]. Among the ME materials, compared with single-phase compounds, ME composites exhibit giant ME coupling response realized through product property between ferromagnetic and ferroelectric subsystems [1, 3, 6–8]. Furthermore, ME coefficients of these composites could be tuned via controlling the volume ratio between the subsystems [8]. Up to now, researchers have adopted various methods to prepare ME composites with different connectivity patterns [8, 9]. For example, Park et al. used aerosol-deposition (AD) technique to prepare 3-2 thick film composites with a giant ME coefficient of 150 mV cm-1 Oe-1 [10]. Additionally, in order to enhance the mechanical coupling coefficient of ME composites, Li et al. reported a disk-ring structure [11]. Recently, Nan et al. reviewed the different structural ME composites prepared by bonding Terfenol-D alloy and piezoelectric materials [8]. Although these ME composites with different working modes yield strong ME effects [8], it is difficult to inves