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Annapureddy, V.,Choi, J. J.,Kim, J. W.,Hahn, B. D.,Ahn, C. W.,Ryu, J. 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol. No.
<P>The effects of crystalline orientation on the ferroelectric properties of lead zirconate titanate (PZT) thick films deposited on (111)-oriented Pt/Ti/SiO2/Si substrates by using a modified spincoating method have been studied. The texture and the microstructure of the thick films were characterized by using X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis, respectively. The XRD results implied that the texture of the PZT films was sensitive to the pyrolysis conditions after spin-coating, but less dependent on the film's thickness. The texture had mainly a (111)-orientation for pyrolysis temperatures from 330 to 400 au broken vertical bar C, and changes in the (100)- orientation occurred for pyrolysis temperatures at or above 450 au broken vertical bar C after annealing at 650 au broken vertical bar C for 5 min. The formation of a preferred texture could be explained by using the intermetallic phases and the internal stress energies between the substrate and the film. The ferroelectric properties of the PZT films fabricated by using this method have been found to be enhanced as compared to those of the PZT films fabricated by using the conventional spin-coating method and to be correlated to the microstructure of the film.</P>
Annapureddy, Venkateswarlu,Palneedi, Haribabu,Yoon, Woon-Ha,Park, Dong-Soo,Choi, Jong-Jin,Hahn, Byung-Dong,Ahn, Cheol-Woo,Kim, Jong-Woo,Jeong, Dae-Yong,Ryu, Jungho Elsevier Sequoia 2017 Sensors and actuators. A Physical Vol.260 No.-
<P><B>Abstract</B></P> <P>This study reports of an <I>ac</I> magnetic field sensor with pT/√Hz sensitivity based on self-biased magnetoelectric composites made using piezoelectric Pb(Mg<SUB>1/3</SUB>Nb<SUB>2/3</SUB>)O<SUB>3</SUB>-PbZrO<SUB>3</SUB>-PbTiO<SUB>3</SUB> (PMN-PZT) single crystals in macro-fiber form and a magnetostrictive Ni plate. Variation in the loss properties of the PMN-PZT single crystals resulted in a substantial change in the magnetic field sensitivity of the ME based sensors. It was found that the loss factor of the piezoelectric layer was one of the key parameters affecting the magnetic field sensitivity. The ME composite sensor structure employing low-loss piezoelectric single crystals achieved a limit of detection (LOD) in the range of a few pT/√Hz at its resonance frequency (500Hz). This magnitude of sensitivity is much higher than that offered bycommercially available magnetic sensors based on the giant magnetoresistance (GMR) effect or Hall-effect.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Magnetic sensors are designed using self-biased magnetoelectric composites made of piezoelectric PMN-PZT single crystals and magnetostrictive Ni. </LI> <LI> A greatly enhanced magnetic sensitivity in the range of pT/√Hz is obtained from the ME composite based sensor, which is better than that of commercial magnetic sensors. </LI> <LI> The loss factor of the piezoelectric layer is an important parameter affecting the magnetic field sensitivity. </LI> </UL> </P>
Exceeding milli-watt powering magneto-mechano-electric generator for standalone-powered electronics
Annapureddy, Venkateswarlu,Na, Suok-Min,Hwang, Geon-Tae,Kang, Min Gyu,Sriramdas, Rammohan,Palneedi, Haribabu,Yoon, Woon-Ha,Hahn, Byung-Dong,Kim, Jong-Woo,Ahn, Cheol-Woo,Park, Dong-Soo,Choi, Jong-Jin,J The Royal Society of Chemistry 2018 ENERGY AND ENVIRONMENTAL SCIENCE Vol.11 No.4
<P>In contrast to typical magnetic energy generators that use electromagnetic induction, which are bulky and have low generation efficiency under small magnetic fields at low frequency, magneto-mechano-electric (MME) generators utilizing the magnetoelectric (ME) coupling effect and magnetic interactions are considered promising candidates. MME generators will serve as a ubiquitous autonomous energy source converting stray magnetic noise to useful electric energy for applications in wireless sensor networks (WSN) for the Internet of Things (IoT) and low-power-consuming electronics. The key component in a MME generator is the ME composite consisting of piezoelectric and magnetostrictive materials, which elastically couples the electric and magnetic behaviour of the respective constituent. Here, we report a MME generator consisting of a crystallographically oriented Pb(Mg1/3Nb2/3)O3-Pb(Zr,Ti)O3piezoelectric single crystal macro-fibre composite and a highly textured magnetostrictive Fe-Ga alloy, which exhibits an exceptionally high rectified DC output power density of 3.22 mW cm<SUP>−3</SUP>. The large energy generation in this structure is ascribed to the coupling between the strong anisotropic properties of the piezoelectric single crystal fibres and textured Fe-Ga magnetostrictive alloy. A smart watch with IoT sensors was driven by the MME generator under a 700 μT magnetic field.</P>
Cantilever Beam with Trapezoidal Cavity for Improved Energy Harvesting
Annapureddy Rami Reddy,Mangalanathan Umapathy,Deenadayalan Ezhilarasi,Gandhi Uma 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.
This paper presents a cantilever structure as energy harvester by introducing a trapezoidal cavity to increase the amplitude of the generated voltage and the overall mechanical to electrical energy conversion efficiency. An analytical model of the proposed structure is developed using Euler-Bernoulli beam theory. The effect of taper angle of the trapezoidal cavity and the neutral axis shift on the generated voltage is analyzed using analytical model and through experimentation. The generated output voltage from the energy harvester with trapezoidal cavity is compared with the beam having rectangular cavity and the beam without cavity. The generated voltage for the beam with trapezoidal cavity is 97.5% and 108% higher as compared with the beam having rectangular cavity and the beam without cavity. The characteristics of the energy harvester are evaluated through analytical model and experimentation and the results are in close agreement.
Annapureddy, Venkateswarlu,Kang, Joo-Hee,Palneedi, Haribabu,Kim, Jong-Woo,Ahn, Cheol-Woo,Choi, Si-Young,Johnson, Scooter David,Ryu, Jungho Elsevier Science Publishers 2017 Journal of the European Ceramic Society Vol. No.
<P><B>Abstract</B></P> <P>In this report a simple and low-cost technique for growing highly textured barium hexaferrite ceramics without the need for flux or seed crystals to achieve grain orientation is demonstrated. Plate-like shaped barium hexaferrite particles were synthesized using a solid-state reaction process and then aligned under a weak magnetic field, followed by uniaxial compaction. The aligned hexaferrite particles appear to serve as seeds, forming textured grains during sintering. The development of texture was verified by X-ray diffraction (XRD), electron backscatter diffraction (EBSD), and vibration sample magnetometer (VSM) measurements. The prepared high-quality hexaferrite ceramics exhibited good anisotropic magnetic properties, comparable to those of single crystal counterparts. A mechanism for the formation of the self-textured grain growth of the barium hexaferrite ceramics, which involves grain boundary and lattice diffusion and interface reaction processes, is proposed.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Venkateswarlu Annapureddy,Jong-Jin Choi,Jong-Woo Kim,Byung-Dong Hahn,Cheol-Woo Ahn,Jungho Ryu 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.68 No.12
The effects of crystalline orientation on the ferroelectric properties of lead zirconate titanate (PZT) thick films deposited on (111)-oriented Pt/Ti/SiO2/Si substrates by using a modified spincoating method have been studied. The texture and the microstructure of the thick films were characterized by using X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis, respectively. The XRD results implied that the texture of the PZT films was sensitive to the pyrolysis conditions after spin-coating, but less dependent on the film’s thickness. The texture had mainly a (111)-orientation for pyrolysis temperatures from 330 to 400 C, and changes in the (100)- orientation occurred for pyrolysis temperatures at or above 450 C after annealing at 650 C for 5 min. The formation of a preferred texture could be explained by using the intermetallic phases and the internal stress energies between the substrate and the film. The ferroelectric properties of the PZT films fabricated by using this method have been found to be enhanced as compared to those of the PZT films fabricated by using the conventional spin-coating method and to be correlated to the microstructure of the film.
Dual-stimulus magnetoelectric energy harvesting
Chu, Zhaoqiang,Annapureddy, Venkateswarlu,PourhosseiniAsl, MohammadJavad,Palneedi, Haribabu,Ryu, Jungho,Dong, Shuxiang Cambridge University Press (Materials Research Soc 2018 MRS bulletin Vol.43 No.3
<▼1><B>Abstract</B><P/></▼1><▼2><P>Harvesting energy from otherwise wasted resources has been intensively investigated as a promising technology especially for enabling the deployment of autonomous wireless-sensor networks for the Internet of Things. Multi-stimulus energy harvesting, simultaneously from different energy sources, provides an attractive opportunity to amplify the power density of harvesters, thereby extending their potential for self-powered devices. In this article, we review recent and ongoing research efforts aimed at enhancing the energy-harvesting performance of magnetoelectric (ME) composite harvesters employing dual stimuli, mechanical vibrations, and magnetic fields. After a brief introduction to vibration, magnetic field, and dual-mode energy harvesting, we survey the key materials utilized for ME energy harvesting. We then focus on progress in this area and discuss relevant ideas to realize electromechanical and magnetoelectric coupling for harvesting energy from mechanical vibrations and magnetic fields simultaneously. We provide perspectives and future directions as well.</P></▼2>
Lim, Kyung-Won,Peddigari, Mahesh,Annapureddy, Ventateswarlu,Hwang, Geon-Tae,Choi, Jong-Jin,Kim, Ga-Yeon,Yi, Sam Nyung,Ryu, Jungho Elsevier 2018 THIN SOLID FILMS - Vol.660 No.-
<P><B>Abstract</B></P> <P>Capacitors with high energy density and high discharging rate have been attracting attention for electric vehicles and military applications, in which the rapid discharge of large amounts of electric energy is required. Since ferroelectric thin film of perovskite structure has different polarization characteristics according to its crystallographic orientation, the charged energy density can be tailored. In this study, we investigated the effect of the crystallographic orientation of Pb(Zr<SUB>0.52</SUB>Ti<SUB>0.48</SUB>)O<SUB>3</SUB> (PZT) thin films grown by chemical solution deposition on the energy storage capability and discharging rate. The {001} and randomly oriented PZT thin films were prepared and their dielectric and ferroelectric properties, stored energy densities, and discharging rates were characterized. The storage energy density of {001}-oriented film was found to be superior to that of other films, while its efficiency was nearly the same. It is believed that {001} oriented PZT thin film has potential for use in high performance capacitors with large energy density.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Highly {001}-oriented ferroelectric PZT thin film grown by chemical solution deposition </LI> <LI> Energy storage density of the {001}-oriented PZT film reached 8.4 J/cm<SUP>3</SUP> at 80 MV/m </LI> <LI> Discharge time of the {001}-oriented PZT film was 4.1 μs at 27 MV/m </LI> </UL> </P>