A Magnetoelectric Laminate Based Passive Micro-Displacement Sensor

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Phys. Status Solidi RRL, 1–3 (2012) / DOI 10.1002/pssr.201206481

A magnetoelectric laminate based passive micro-displacement sensor 1 2

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Schematic diagram of the suggested micro-displacement sensor based on magnetostrictive/piezoelectric magnetoelectric laminate. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Zheng Wu1, 2, Jun Zhang1, Ke Ma1, Yi Cao1, Yanmin Jia*, 1, Haosu Luo3, and Yihe Zhang4 Department of Physics, Zhejiang Normal University, Jinhua 321004, P.R. China College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, P.R. China 3 Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800, P.R. China 4 School of Materials Science and Technology, China University of Geosciences, Beijing 100083, P.R. China Received 8 November 2012, revised 27 November 2012, accepted 27 November 2012 Published online 29 November 2012 Keywords magnetoelectrics, laminates, displacement sensors, piezoelectrics *

Corresponding author: e-mail yanmin_jia@yahoo.com.cn, Phone: +86 579 8229 8979, Fax: +86 579 8229 8188

A passive micro-displacement sensor (for ~ μm displacement) was fabricated based on a magnetoelectric laminate, in which the displacement change can result in a change of the magnetic flux around the magnetoelectric sensor. The displacement measurement was realized by measuring the magnetoelectric output voltage. The displacement detecting coefficient was ~ 2.5 mV/μm at a frequency of ~ 1 kHz. This passive displacement sensor possesses the advantages of low cost, high resolution, low energy consumption and good linearity and has potential for application in future displacement detectors.

1 Introduction The measurement of displacement or position is one of the most important and oldest tasks in sensor technology [1, 2]. Currently, the two main kinds of displacement sensors in practical application are based on optical and magnetic detecting technology [1, 2]. The optical displacement sensor is high resolution (~0.1 μm) and expensive, while the magnetic one is low resolution (~10 μm) and cheap. Developing magnetic displacement sensors with high detecting resolution is necessary for many applications in the automotive, hydraulic press, container security and food industries [3, 4]. In recent years, the magnetostrictive/piezoelectric magnetoelectric (ME) laminates have attracted considerable attention because of their ultrahigh magnetic-field sensitivity (~nT) [5, 6]. The ME conversion in the composites has been attributed to the joint effect of the magnetostrictive and the piezoelectric effect. The interestingly large ME coefficient of 384 mV/Oe has been reported in laminated composites composed of the magnetostrictive

TbxDy1–xFe2–y (Terfenol-D) alloy and the piezoelectric Pb(Mg1/3Nb2/3)1–xTixO3 (PMN-PT) crystal [7]. In this work, a passive ~μm ME displacement sensor was suggested and fabricated. 2 Experiment Figure 1 illustrates a schematic diagram of the suggested micro-displacement sensor, which consists of a permanent magnet to provide a dc bias magnetic field, some high-μ metal Fe yokes, a vibration Fe plate adhered to a shaker to generate the displacement, and a ME laminate to detect the magnetic field intensity. In our structure, the intrinsic magnetic flux in the permanent magnet keeps constant. On basis of Kirchhoff's First Law on the magnetic circuit, the change of the air gap can induce a change in the magnetic flux around the ME laminate. Then the displacement measurement can be realized by monitoring the ME output voltage. The displacement of the Fe plate was generated by a shaker (Ling Dynamic Systems Ltd., model type V406) connected with a power © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

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