Browsing by Author "Zhou, Yuan"

Now showing 1 - 8 of 8
  • Thumbnail Image
    Anisotropic self-biased dual-phase low frequency magneto-mechano-electric energy harvesters with giant power densities
    Patil, Deepak Rajaram; Zhou, Yuan; Kang, Ju-Eun; Sharpes, Nathan; Jeong, Dae-Young; Kim, Yang-Do; Kim, Kee Hoon; Priya, Shashank; Ryu, Jungho (AIP Publishing, 2014-04-02)
    We report the physical behavior of self-biased multi-functional magneto-mechanoelectric (MME) laminates simultaneously excited by magnetic and/or mechanical vibrations. The MME laminates composed of Ni and single crystal fiber composite exhibited strong ME coupling under Hdc = 0 Oe at both low frequency and at resonance frequency. Depending on the magnetic field direction with respect to the crystal orientation, the energy harvester showed strong in-plane anisotropy in the output voltage and was found to generate open circuit output voltage of 20Vpp and power density of 59.78 mW/Oe² g² cm³ under weak magnetic field of 1 Oe and mechanical vibration of 30 mg, at frequency of 21 Hz across 1 MΩ resistance.
  • Thumbnail Image
    Dual-phase self-biased magnetoelectric energy harvester
    Zhou, Yuan; Apo, Daniel J.; Priya, Shashank (AIP Publishing, 2013-11-01)
    We report a magnetoelectric energy harvester structure that can simultaneously scavenge magnetic and vibration energy in the absence of DC magnetic field. The structure consisted of a piezoelectric macro-fiber composite bonded to a Ni cantilever. Large magnetoelectric coefficient similar to 50 V/cm Oe and power density similar to 4.5 mW/cm(3) (1 g acceleration) were observed at the resonance frequency. An additive effect was realized when the harvester operated under dual-phase mode. The increase in voltage output at the first three resonance frequencies under dual-phase mode was found to be 2.4%, 35.5%, and 360.7%. These results present significant advancement toward high energy density multimode energy harvesting system. (C) 2013 AIP Publishing LLC.
  • Thumbnail Image
    Giant self-biased magnetoelectric coupling in co-fired textured layered composites
    Yan, Yongke; Zhou, Yuan; Priya, Shashank (AIP Publishing, 2013-02-01)
    Co-fired magnetostrictive/piezoelectric/magnetostrictive laminate structure with silver inner electrode was synthesized and characterized. We demonstrate integration of textured piezoelectric microstructure with the cost-effective low-temperature co-fired layered structure to achieve strong magnetoelectric coupling. Using the co-fired composite, a strategy was developed based upon the hysteretic response of nickel-copper-zinc ferrite magnetostrictive materials to achieve peak magnetoelectric response at zero DC bias, referred as self-biased magnetoelectric response. Fundamental understanding of self-bias phenomenon in composites with single phase magnetic material was investigated by quantifying the magnetization and piezomagnetic changes with applied DC field. We delineate the contribution arising from the interfacial strain and inherent magnetic hysteretic behavior of copper modified nickel-zinc ferrite towards self-bias response. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4791685]
  • Thumbnail Image
    Giant strain with ultra-low hysteresis and high temperature stability in grain oriented lead-free K0.5Bi0.5TiO3-BaTiO3-Na0.5Bi0.5TiO3 piezoelectric materials
    Maurya, Deepam; Zhou, Yuan; Wang, Yaojin; Yan, Yongke; Li, Jiefang; Viehland, Dwight D.; Priya, Shashank (Springer Nature, 2015-02-26)
    We synthesized grain-oriented lead-free piezoelectric materials in (K0.5Bi0.5TiO3-BaTiO3-xNa(0.5)Bi(0.5)TiO(3) (KBT-BT-NBT) system with high degree of texturing along the [001]c (c-cubic) crystallographic orientation. We demonstrate giant field induced strain (similar to 0.48%) with an ultra-low hysteresis along with enhanced piezoelectric response (d(33) similar to 190pC/N) and high temperature stability (similar to 160 degrees C). Transmission electron microscopy (TEM) and piezoresponse force microscopy (PFM) results demonstrate smaller size highly ordered domain structure in grain-oriented specimen relative to the conventional polycrystalline ceramics. The grain oriented specimens exhibited a high degree of non-180 degrees domain switching, in comparison to the randomly axed ones. These results indicate the effective solution to the lead-free piezoelectric materials.
  • Thumbnail Image
    Integration of lead-free ferroelectric on HfO2/Si (100) for high performance non-volatile memory applications
    Kundu, Souvik; Maurya, Deepam; Clavel, Michael B.; Zhou, Yuan; Halder, Nripendra N.; Hudait, Mantu K.; Banerji, Pallab; Priya, Shashank (Nature Publishing Group, 2015-02-16)
    We introduce a novel lead-free ferroelectric thin film (1-x)BaTiO3-xBa(Cu1/3Nb2/3)O3 (x 5 0.025) (BT-BCN) integrated on to HfO2 buffered Si for non-volatile memory (NVM) applications. Piezoelectric force microscopy (PFM), x-ray diffraction, and high resolution transmission electron microscopy were employed to establish the ferroelectricity in BT-BCN thin films. PFMstudy reveals that the domains reversal occurs with 1806 phase change by applying external voltage, demonstrating its effectiveness forNVMdevice applications. X-ray photoelectron microscopy was used to investigate the band alignments between atomic layer deposited HfO2 and pulsed laser deposited BT-BCN films. Programming and erasing operations were explained on the basis of band-alignments. The structure offers large memory window, low leakage current, and high and low capacitance values that were easily distinguishable even after ,106 s, indicating strong charge storage potential. This study explains a new approach towards the realization of ferroelectric based memory devices integrated on Si platform and also opens up a new possibility to embed the system within current complementary metal-oxide-semiconductor processing technology.
  • Thumbnail Image
    Magnetoelectric Composites for On-Chip Near-Resonance Applications
    Zhou, Yuan (Virginia Tech, 2014-09-08)
    Magnetoelectric (ME) effect is defined as the change in dielectric polarization (P) of a material under an applied magnetic field (H) or an induced magnetization (M) under an external electric field (E). ME materials have attracted number of investigators due to their potential for improving applications such as magnetic field sensors, filters, transformers, memory devices and energy harvesters. It has been shown both experimentally and theoretically that the composite structures consisting of piezoelectric and magnetostrictive phases possess stronger ME coupling in comparison to that of single phase materials. Giant magnetoelectric effect has been reported in variety of composites consisting of bulk-sized ME composites and thin film ME nanostructures. In this dissertation, novel ME composite systems are proposed, synthesized and characterized in both bulk and thin films to address the existing challenges in meeting the needs of practical applications. Two applications were the focused upon in this study, tunable transformer and dual phase energy harvester, where requirements can be summarized as: high ME coefficient under both on-resonance and off-resonance conditions, broad bandwidth, and low applied DC bias. In the first chapter, three challenges related to the conventional ME behavior in bulk ME composites have been addressed (1) The optimized ME coefficient can be achieved without external DC magnetic field by using a self-biased ME composite with a homogenous magnetostrictive material. The mechanism of such effect and its tunability are studied; (2) A near-flat ME response regardless of external magnetic field is obtained in a self-biased ME composite with geometry gradient structure; (3) By optimizing interfacial coupling with co-firing techniques, the ME coefficient can be dramatically enhanced. Theses co-fired ME laminates not only exhibit high coupling coefficient due to direct bonding, but also illustrate a self-biased effect due to the built-in stress during co-sintering process. These results present significant advancement toward the development of multifunctional ME devices since it eliminates the need for DC bias, expands the working bandwidth and enhances the ME voltage coefficient. Next, magnetoelectric nanocomposites were developed for understanding the nature of the growth of anisotropic thin film structures. In this chapter following aspects were addressed: (1) Controlled growth of nanostructures with well-defined morphology was obtained. Microstructure and surface morphology evolution of the piezoelectric BaTiO3 films was systematically analyzed. A growth model was proposed by considering the anisotropy of surface energy and the formation of twin lamellae structure within the frame work of Structure Zone Model (SZM) and Dynamic Scaling Theory (DST). In parallel to BaTiO3 films, well-ordered nanocomposite arrays [Pb1.1(Zr0.6Ti0.4)O3/CoFe2O4] with controlled grain orientation were developed and investigated by a novel hybrid deposition method. The influence of the pre-deposited template film orientation on the growth of ME composite array was studied. (2) PZT/CFO/PZT thick composite film and BTO/CFO thin film were synthesized using sol-gel deposition (SGD) and pulsed laser deposition (PLD) techniques, respectively. The HRTEM analysis revealed local microstructure at the interface of consecutive constituents. The interfacial property variation of these films was found to affect the coupling coefficient of corresponding ME nanocomposites. Subsequently, a novel complex three-dimensional ME composite with highly anisotropic structure was developed using a hybrid synthesis method. The influence of growth condition on the microstructure and property of the grown complex composites was studied. The film with highly anisotropic structure was found to possess tailored ferroelectric response indicating the promise of this synthesis method and microstructure. Based on the laminated ME composites, three types of ME tunable transformer designs were designed and fabricated. The goal was to develop a novel ME transformer with tunable performance (voltage gain and/or working resonance frequency) under applied DC magnetic field. Conventional ME transformers need either winding coil or large external magnetic field to achieve the tunable feature. Considering the high ME coupling of ME laminate, two ME transformers were developed by epoxy bonding Metglas with transversely/longitudinally poled piezoelectric ceramic transformer. The influence of different operation modes toward magnetoelectric tunability was analyzed. In addressing the concern of the epoxy bonding interface, a co-fired ME transformer with unique piezoelectric transformer/magnetostrictive layer/piezoelectric transformer trilayer structure was designed. The design and development strategy of thin film ME transformer was discussed to illustrate the potential for ME transformer miniaturization and on-chip integration. Lastly, motivated by the increasing demand of energy harvesting (EH) systems to support self-powered sensor nodes in structural health monitoring system, a magnetoelectric composite based energy harvester was developed. The development and design concept of the magnetoelectric energy harvester was systematically discussed. In particular, the first dual-phase self-biased ME energy harvester was designed which can simultaneously harness both vibration and stray magnetic field (Hac) in the absence of DC magnetic field. Strain distribution of the EH was simulated using the finite element model (FEM) at the first three resonance frequencies. Additionally, the potential of transferring this simple EH structure into MEMS scalable components was mentioned. These results provide significant advancement toward high energy density multimode energy harvesting system.
  • Thumbnail Image
    Near-flat self-biased magnetoelectric response in geometry gradient composite
    Zhou, Yuan; Priya, Shashank (American Institute of Physics, 2014-03-14)
    We demonstrate a near-flat self-biased magnetoelectric (ME) effect in geometry gradient magnetostrictive-piezoelectric laminates. The near-flat behavior was characterized by a stable ME response over a wide range of magnetic DC bias. By adjusting the configuration of the magnetostrictive layer, we were able to control the magnitude of the self-biased magnetoelectric coefficient. The ME response was found to be almost independent of the applied DC bias in the range of 0 similar to 260 Oe. This bandwidth was almost 650% similar to 3800% higher than that of the conventional ME composites. This significant advancement opens great potential towards the development of high stability/sensitivity magnetic field sensors and energy harvesters. (C) 2014 AIP Publishing LLC.
  • Thumbnail Image
    Tunable self-biased magnetoelectric response in homogenous laminates
    Zhou, Yuan; Yang, Su-Chul; Apo, Daniel J.; Maurya, Deepam; Priya, Shashank (AIP Publishing, 2012-12-01)
    In this study, we demonstrate self-biased magnetoelectric effect in homogenous two-phase magnetostrictive-piezoelectric laminates. Our results illustrate the method for tuning the magnitude of self-bias effect and provide understanding behind the hysteretic changes. We model this phenomenon by considering the magnetization hysteresis with shape-induced demagnetization effect. The self-biased response was found to be directly related to the nature of magnetization and can be tuned by variation in demagnetization state and the resultant differential magnetic flux distribution. These results present significant advancement toward development of AC magnetic field sensor and magnetoelectric composite based on-chip devices by eliminating the need for DC bias. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4769365]