Browsing by Author "Li, Jiefang"

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    An acoustic position sensor
    Dong, Shuxiang; Bai, Feiming; Li, Jiefang; Viehland, Dwight D. (AIP Publishing, 2003-11-01)
    This article presents an acoustic method-the resonance acoustic field sensor or piezoelectric-sound-resonance cavity (PSRC)-for object position detection. This method utilizes the change of acoustic radiation impedance as a sensing mechanism. The PSRC both generates and detects a resonance acoustic field, along both the axial and transverse directions. We have discovered that an inserted object or an object motion in the sound radiation field results in changes in both the voltage and phase of the PSRC. Results have shown that a minimum object displacement of <10 mum can be detected in the axial direction (and <100 mum in the transverse) by this method. (C) 2003 American Institute of Physics.
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    Adaptive ferroelectric states in systems with low domain wall energy: Tetragonal microdomains
    Jin, Y. M.; Wang, Yu. U.; Khachaturyan, Armen G.; Li, Jiefang; Viehland, Dwight D. (American Institute of Physics, 2003-09-01)
    Ferroelectric and ferroelastic phases with very low domain wall energies have been shown to form miniaturized microdomain structures. A theory of an adaptive ferroelectric phase has been developed to predict the microdomain-averaged crystal lattice parameters of this structurally inhomogeneous state. The theory is an extension of conventional martensite theory, applied to ferroelectric systems with very low domain wall energies. The case of ferroelectric microdomains of tetragonal symmetry is considered. It is shown for such a case that a nanoscale coherent mixture of microdomains can be interpreted as an adaptive ferroelectric phase, whose microdomain-averaged crystal lattice is monoclinic. The crystal lattice parameters of this monoclinic phase are self-adjusting parameters, which minimize the transformation stress. Self-adjustment is achieved by application of the invariant plane strain to the parent cubic lattice, and the value of the self-adjusted parameters is a linear superposition of the lattice constants of the parent and product phases. Experimental investigations of Pb(Mg1/3Nb2/3)O-3-PbTiO3 and Pb(Zn1/3Nb2/3)O-3-PbTiO3 single crystals confirm many of the predictions of this theory. (C) 2003 American Institute of Physics.
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    Aging associated domain evolution in the orthorhombic phase of < 001 > textured (K0.5Na0.5)Nb0.97Sb0.03O3 ceramics
    Yao, Jianjun; Li, Jiefang; Viehland, Dwight D.; Chang, Y. F.; Messing, G. L. (AIP Publishing, 2012-03-01)
    Aging effect due to domain evolution in (K-0.5,Na-0.5)Nb0.97Sb0.03O3 < 001 > textured ceramics was investigated by piezoresponse force microscopy. We find that aging effect is pronounced in the orthorhombic single phase field. A more uniform and finer domain structure on the order of several hundred nanometers was observed after aging and is believed to originate from defect-migration. After poling, large domains (similar to 10 mu m) with smooth boundaries were found in the aged condition due to the more readily redistribution of uniform and finer domain structures after aging. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3698154]
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    Alternating and direct current field effects on the structure-property relationships in Na0.5Bi0.5TiO3-x% BaTiO3 textured ceramics
    Ge, Wenwei; Maurya, Deepam; Li, Jiefang; Priya, Shashank; Viehland, Dwight D. (AIP Publishing, 2013-06-01)
    The influence of alternating (ac) and direct current (dc) fields on the structural and dielectric properties of [001](PC) textured Na0.5Bi0.5TiO3-7%BaTiO3 (NBT-7%BT) ceramics has been investigated. X-ray diffraction measurements revealed that the depolarization at temperature T-d in poled samples resulted from a tetragonal -> pseudo-cubic transition on heating. Moderate ac drive and dc bias had opposite influences on T-d: ac drive decreased the T-d, whereas dc bias increased it. These investigations suggested an effective method to expand the working temperature range of NBT-x%BT textured ceramics to a high temperature. (C) 2013 AIP Publishing LLC.
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    Anhysteretic field-induced rhombhohedral to orthorhombic transformation in <110>-oriented 0.7Pb(Mg1/3Nb2/3)O-3-0.3PbTiO(3) crystals
    Viehland, Dwight D.; Li, Jiefang (American Institute of Physics, 2002-12-15)
    The electric-field induced polarization (P-E) and strain (epsilon-E) characteristics of <110>(c)-oriented 0.7Pb(Mg1/3Nb2/3)O-3-0.3PbTiO(3) crystals have been investigated, under both unipolar and bipolar drive. A field-induced transformation was observed below saturation. Under unipolar drive, the P-E and epsilon-E loops were anhysteretic even at the transformation point, demonstrating complete reversibility between ferroelectric rhombohedral and orthorhombic phases. The results show that "polarization rotation" can occur between <111>(c) and <110>(c), where the polarization is confined to the (100)(c) in a monoclinic M-b type symmetry. (C) 2002 American Institute of Physics.
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    Characterization of Laminated Magnetoelectric Vector Magnetometers to Assess Feasibility for Multi-Axis Gradiometer Configurations
    Berry, David (Virginia Tech, 2010-11-19)
    Wide arrays of applications exist for sensing systems capable of magnetic field detection. A broad range of sensors are already used in this capacity, but future sensors need to increase sensitivity while remaining economical. A promising sensor system to meet these requirements is that of magnetoelectric (ME) laminates. ME sensors produce an electric field when a magnetic field is applied. While this ME effect exists to a limited degree in single phase materials, it is more easily achieved by laminating a magnetostrictive material, which deforms when exposed to a magnetic field, to a piezoelectric material. The transfer of strain from the magnetostrictive material to the piezoelectric material results in an electric field proportional to the induced magnetic field. Other fabrication techniques may impart the directionality needed to classify the ME sensor as a vector magnetometer. ME laminate sensors are more affordable to fabricate than competing vector magnetometers and with recent increases in sensitivity, have potential for use in arrays and gradiometer configurations. However, little is known about their total field detection, the effects of multiple sensors in close proximity and the signal processing needed for target localization. The goal for this project is to closely examine the single axis ME sensor response in different orientations with a moving magnetic dipole to assess the field detection capabilities. Multiple sensors were tested together to determine if the response characteristics are altered by the DC magnetic bias of ME sensors in close proximity. And finally, the ME sensor characteristics were compared to alternate vector magnetometers.
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    Characterization of magnetoelectric laminate composites operated in longitudinal-transverse and transverse-transverse modes
    Dong, Shuxiang; Li, Jiefang; Viehland, Dwight D. (American Institute of Physics, 2004-03-01)
    Magnetostrictive and piezoelectric laminate composites of terfenol-D and Pb(Zr1-xTix)O-3 have been studied. The magnetoelectric (ME) coefficients have been characterized for the different operational modes: (i) a longitudinally magnetized and transversely polarized longitudinal transverse (LT) mode, and (ii) a transversely magnetized and transversely polarized transverse-transverse (TT) mode. The results demonstrate that the (LT) magnetoelectric mode has dramatically higher ME coefficients than the TT one. The LT magnetoelectric coefficient is up to 5-7 times larger than the TT one, when operated in low magnetic bias ranges. (C) 2004 American Institute of Physics.
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    Circumferential-mode, quasi-ring-type, manetoelectric laminate composite - a highly sensitive electric current and/or vortex magnetic field sensor
    Dong, Shuxiang; Bai, J. G.; Zhai, Junyi; Li, Jiefang; Lu, G. Q.; Viehland, Dwight D.; Zhang, S. J.; Shrout, T. R. (AIP Publishing, 2005-05-01)
    A quasi-ring-type magnetoelectric (ME) laminate composite consisting of a circumferentially poled piezoelectric Pb(Zn1/3Nb2/3O)(3-)4.5 at.% PbTiO(3)single-crystal ring and two circumferentially magnetized magnetostrictive TERFENOL-D rings was fabricated and found to have a giant ME voltage coefficient of 2.2 V/Oe, or equivalently a ME field coefficient of 5.5 V/cm Oe, over the frequency range of 0.5 < f < 10(5) Hz. This circumferential-mode quasiring ME laminate can detect ac currents (noncontact) as small as 10(-7) A, and/or a vortex magnetic field as small as 6 x 10(-12) Tesla. In addition, we demonstrated current sensing capability of the quasiring laminate in a power electronics module. (c) 2005 American Institute of Physics.
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    Comparison of noise floor and sensitivity for different magnetoelectric laminates
    Gao, Junqi; Das, Jaydip; Xing, Zengping; Li, Jiefang; Viehland, Dwight D. (American Institute of Physics, 2010-10-15)
    We present a comparison of the magnetoelectric (ME) response and magnetic-field sensitivities of engineered laminate sensors comprised of magnetostrictive and piezoelectric phases. The ME voltage coefficients for Metglas and single crystal fibers of Pb(Mg1/3Nb2/3) O-3-PbTiO3 (PMN-PT) or Pb(Zn1/3Nb2/3) O-3-PbTiO3 (PZN-PT) are about 2.8 times larger than those with Metglas-Pb(Zr, Ti)O-3 (PZT) ceramic ones. This results in a 1.7 times enhancement in the magnetic-field sensitivity for the structures with single crystals. Accordingly, the noise floors are about three to four times lower for composites with PMN-PT or PZN-PT fibers than those with PZT. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3486483]
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    Comparisons of polarization switching in "hard," "soft," and relaxor ferroelectrics
    Jullian, Christelle; Li, Jiefang; Viehland, Dwight D. (American Institute of Physics, 2004-04-15)
    The dynamics of polarization switching have been investigated over extremely broad time (10(-8)
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    Conformal miniaturization of domains with low domain-wall energy: Monoclinic ferroelectric states near the morphotropic phase boundaries
    Jin, Y. M.; Wang, Yu. U.; Khachaturyan, Armen G.; Li, Jiefang; Viehland, Dwight D. (American Physical Society, 2003-11-07)
    A theory is developed for intermediate monoclinic (FEm) phases near morphotropic phase boundaries in ferroelectrics of complex oxides. It is based on the conformal miniaturization of stress-accommodating tetragonal domains under the condition of low domain-wall energy density. The microdomain-averaged lattice parameters are determined and attributed to the parameters of an adaptive monoclinic phase. The theory is applied to the temperature, electric field, and compositional dependent FEm lattice parameters. The predictions of the theory are rigidly obeyed over the entire FEm stability range.
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    Conformal sensor skin approach to the safety-monitoring of H-2 fuel tanks
    Dong, Shuxiang; Cao, Hu; Bai, Feiming; Yan, Li; Li, Jiefang; Viehland, Dwight D.; Gao, Y. K. (AIP Publishing, 2004-05-01)
    A conformal sensor skin approach has been developed for safety monitoring of H-2 fuel tanks. Small piezoelectrically driven sound resonance cavities were embedded in a porous polymer. When placed on a structural composite plate, it was found feasible to detect the leakage of small concentrations of H-2 in real time. (C) 2004 American Institute of Physics.
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    Control of magnetic and electric responses with electric and magnetic fields in magnetoelectric heterostructures
    Das, J.; Li, M.; Kalarickal, S. S.; Altmannshofer, S.; Buchanan, K. S.; Li, Jiefang; Viehland, Dwight D. (AIP Publishing, 2010-05-01)
    This paper reports on the tuning of both magnetic and electric responses with electric and magnetic fields for metglas-Pb(Zr,Ti)O(3) based magnetoelectric (ME) heterostructures that can be promising for communication and sensor applications. The hysteresis loop results indicate a change in the in-plane magnetization due to application of voltages that leads to a tuning of the ferromagnetic resonance frequency by up to about 210 MHz with electric field. Furthermore, these structures show a high ME voltage coefficient that results in the detection of a 2 nT ac magnetic field and a low noise floor. (C) 2010 American Institute of Physics. [doi:10.1063/1.3443715]
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    Controlled growth of epitaxial BiFeO3 films using self-assembled BiFeO3-CoFe2O4 multiferroic heterostructures as a template
    Li, Yanxi; Yang, Yaodong; Yao, Jianjun; Viswan, Ravindranath; Wang, Z. G.; Li, Jiefang; Viehland, Dwight D. (AIP Publishing, 2012-07-01)
    The growth mechanism of a BiFeO3 layer deposited on self assembled (0.65) BiFeO3-(0.35) CoFe2O4 (BFO-CFO) composite thin films was studied. Epitaxial and self-assembled BFO-CFO thin films were deposited on SrTiO3 (111) substrates by pulsed laser deposition and were subsequently used as a seed layer for the deposition of an additional BFO layer. x-ray line scans showed the heterostructures were highly epitaxial. Cross-sectional scanning electron microscopy and focused ion beam images revealed the top BFO layer grew preferentially from BFO nanopillars in the BFO-CFO thin films, thus, demonstrating controlled growth. The multiferroic properties of this new nanostructure were then studied. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4734508]
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    Crystallographic direction dependence of direct current field induced strain and phase transitions in Na0.5Bi0.5TiO3-x%BaTiO3 single crystals near the morphotropic phase boundary
    Luo, Chengtao; Ge, Wenwei; Zhang, Qinhui; Li, Jiefang; Luo, Haosu; Viehland, Dwight D. (AIP Publishing, 2012-10-01)
    The crystallographic dependence of the DC electric (E) field induced strain and phase transition in Na0.5Bi0.5TiO3-5.6%BaTiO3 (NBT-5.6%BT) single crystals has been investigated. An induced transition between pseudocubic and tetragonal structures was observed under E = 10 kV/cm for fields applied along the < 001 > direction, whereas an induced transition between pseudocubic and rhombohedral structures was observed when the E-field was applied along < 111 >. Our results show near the morphotropic phase boundary that the phase stability of NBT-x%BT is dependent on the crystallographic direction along which E was applied. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4757877]
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    Dependence of magnetic field sensitivity of a magnetoelectric laminate sensor pair on separation distance: Effect of mutual inductance
    Li, Menghui; Wang, Yaojin; Gao, Junqi; Gray, David; Li, Jiefang; Viehland, Dwight D. (American Institute of Physics, 2012-02-01)
    The effect of mutual inductance on the performance of a pair of Metglas/Pb(Zr,Ti)O-3 laminate magnetoelectric (ME) sensors has been studied. The effective value of the ME coefficient (alpha(ME)) for the laminates was reduced when the distance between was < 40 mm. Separating the two laminates by distances of > 40 mm, the effect of mutual inductance was small. The laminates exhibited the maximum values of alpha(ME). The ME sensor unit with two laminates connected in parallel had higher magnetic field sensitivities. 2012 American Institute of Physics. [doi:10.1063/1.3684986]
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    Deposition conditions and electrical properties of relaxor ferroelectric Pb(Fe1/2Nb1/2)O-3 thin films prepared by pulsed laser deposition
    Yan, Li; Li, Jiefang; Viehland, Dwight D. (American Institute of Physics, 2007-05-15)
    Epitaxial lead iron niobate thin films with thicknesses of 50 nm < t < 500 nm have been deposited by pulsed laser deposition. We have identified the deposition conditions that result in insulating layers. These critical conditions are essential to (i) prevent semiconducting resistivity characteristics, (ii) achieve higher induced polarizations of 70 mu C/cm(2) under E=190 kV/mm, and (iii) obtain remanent polarizations of 17.7 mu C/cm(2), coercive fields of 9.5 kV/mm, and dielectric constants of similar to 1200 at room temperature. (c) 2007 American Institute of Physics.
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    Destruction of spin cycloid in (111)(c)-oriented BiFeO3 thin films by epitiaxial constraint: Enhanced polarization and release of latent magnetization
    Bai, Feiming; Wang, Junling; Wuttig, Manfred; Li, Jiefang; Wang, Naigang; Pyatakov, Alexander P.; Zvezdin, Anatoly Konstantinovich; Cross, L. E.; Viehland, Dwight D. (AIP Publishing, 2005-01-01)
    In BiFeO3 films, it has been found that epitaxial constraint results in the destruction of a space modulated spin structure. For (111)c films, relative to corresponding bulk crystals, it is shown (i) that the induced magnetization is enhanced at low applied fields; (ii) that the polarization is dramatically enhanced; whereas, (iii) the lattice structure for (111)(c) films and crystals is nearly identical. Our results evidence that eptiaxial constraint induces a transition between cycloidal and homogeneous anti ferromagnetic spin states, releasing a latent antiferromagnetic component locked within the cycloid. (C) 2005 American Institute of Physics.
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    Detection of pico-Tesla magnetic fields using magneto-electric sensors at room temperature
    Zhai, Junyi; Xing, Zengping; Dong, Shuxiang; Li, Jiefang; Viehland, Dwight D. (AIP Publishing, 2006-02-01)
    The measurement of low-frequency (10(-2)-10(3) Hz) minute magnetic field variations (10(-12) Tesla) at room temperature in a passive mode of operation would be critically enabling for deployable neurological signal interfacing and magnetic anomaly detection applications. However, there is presently no magnetic field sensor capable of meeting all of these requirements. Here, we present new bimorph and push-pull magneto-electric laminate composites, which incorporate a charge compensation mechanism (or bridge) that dramatically enhances noise rejection, enabling achievement of such requirements. (c) 2006 American Institute of Physics.
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    Direct high-resolution transmission electron microscopy observation of tetragonal nanotwins within the monoclinic M(C) phase of Pb(Mg(1/3)Nb(2/3))O(3)-0.35PbTiO(3) crystals
    Bhattacharyya, Somnath; Jinschek, J. R.; Cao, Hu; Wang, Yu. U.; Li, Jiefang; Viehland, Dwight D. (AIP Publishing, 2008-04-01)
    We report on the direct observation of tetragonal nanodomains within an average monoclinic M(C) phase of Pb(Mg(1/3)Nb(2/3))O(3)-0.35PbTiO(3) single crystals by high-resolution transmission electron microscopy. These nanodomains are geometrically arranged in alternating layers of twins. The findings are consistent with the fundamental underlying assumptions of the ferroelectric adaptive phase theory.