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Integrated Magnetoelectric Heterostructure and Magnetic Field Sensor

The magnetoelectric (ME) effect has attracted significant interest in recent years due to potential multifunctional devices applications such as passive magnetic field sensors, non-volatile electric-write/magnetic-read memories, etc. In particular, giant ME coupling found in Metglas/piezofiber laminate composite open the possibility of magnetic field sensors applications. The practical usefulness of a magnetic sensor is determined not only by the output signal of the sensor in response to an incident magnetic field, but also by the equivalent magnetic noise generated in the absence of an incident field. 

In this topic, Our central goal is the meaningful ME magnetic sensor,  and we are studying: 1) multi-scale heterostructure design to enhance the linear and nonlinear ME coefficient, including flexible thin flims and rigid bulks  2) cooperative optimization of magnetoelectric materials and the signal process circuit, (3) sensitivity enhancement in the real-world environment for practical applications.


 
Flexible Ferro-electronics for Sense and Energy Conversion Devices

Wearable and implantable biomedical electronics have gained tremendous flurry of research interesting in the past few years with the goal of revolutionary treatment to some chronic diseases. Among them, flexible piezoelectric materials that enables mechanical-to-electrical energy conversion, stimulate tremendous attraction to mechanical energy harvesters and health monitor from the motion of human and organs (see figures below).

In this topic, we are developing flexible highly-efficient ferroelectric, piezoelectric and magnetoelectric materials for:

1) sense application (mechanical sensor for structural health monitoring, magnetoelectronics for magnetic field detection, etc.);

2) energy-conversion devices (piezoelectric/pyroelectric energy harvester, electrocaloric cooling device, etc.)

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(Cited from PNAS, 111(5):1927, 2014; Nature Materials, 14(7):728, 2015)

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(Cited from Journal of Materials Chemistry B 4(18):2999-3018, 2016)


 
Process, properties and physics of ferroelectric materials

1) Microstructural and properties of modified ferroelectric single crystals

In spite of the extraordinary electromechanical properties of Generation I ferroelectric single crystals of PMN-PT and PZN-PT, several obstacles have restricted them from practical applications. First, deterioration in performance with increasing temperature limits their usable temperature ranges. Second, the coercive field is on the order of 2 kV/cm, which restricts their usage to low voltage drive applicationsIn order to overcome these challenges, numerous strategies have been carried out in an attempt to broaden the usable temperature and voltage ranges, including adding solution components (PIN, PSN,et al) and dopants of Mn and Fe.

In this topic, we collabrate with Prof. Haosu Luo of Shanghai Insititute of Ceramics and Prof. Dwight Viehland of Virginia Tech to (i) control the macroproperties by designing the microstructure via post-treatment technices,(ii) clarify the origin of the exceptional piezoelectric characteristics of this new generation of ternary crystals and resolve the complexities of the transformation sequences in detail.

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(Cited from Scientific Reports, 6:35120, 2016)

2) High thermal-stability piezoelectric materials for harsh environment

  Harsh environmental conditions, including extremes of pressure, temperature, radiation, etc., pose a great challenge for conventional piezoelectric-based sensing devices as most existing sensing elements could not survive in such harsh environments. To address these challenge, in this topic, we are working on the thermal stability of piezoelectric thin films and related sense appication via microstructure and composition design, i.e., seeking new material system, dopant induced defect engineering, lattice mismatch induced strain engineering, etc.


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(Cited from Nature Nanotechnology, 6:491, 2011-The ferroelectric tetrogonal phase can be persisted up tp 800 oC due to the strain engineering)


Yaojin Wang (汪尧进) Laboratory of Advanced Sensitive Materials and Devices
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Department of Materials Science and Engineering.Nanjing University of Science and Technology