• 2018 Sino-Korea Workshop on Ferroelectric Materials and Their Applications

    October 19-22, 2018, Nanjing, Jiangsu, China
    The 2018 Sino-Korea Workshop on Ferroelectric Materials and Their Applications (SKWFMA-2018) has been held on October 19-22, 2018 in Nanjing, Jiangsu, China. More than 137 participants from Korea, China and US has been attent the workshop, including 60 invited talks and 33 poster presentations. SKWFMA-2018 is aimed to provide a forum to present and discuss the state-of-the-art developments in ferroelectric materials and their applications, including 1) Ferroelectric ceramics and device applications, and 2) Emergent ferroics and phenomenon, in order to provide a better understanding of the relationship between the multi-scale polar structures and macroscopic properties of ferroelectric materials and related phenomenon, and to design and synthesize novel ferroelectric materials of high-performance for technological applications.
  • Pyro-catalytic hydrogen evolution by Ba0.7Sr0.3TiO3 nanoparticles: harvesting cold-hot alternation e

    Energy & Environmental Science [11:2198-2207, 2018]
    Photocatalytic hydrogen evolution, as an environmental-friendly, energy saving and simple way, has been widely reported. However, there are some important factors that prohibit practical application of photocatalytic hydrogen production, including low efficiency of solar energy utilization, and lack of response in the dark. The temperature fluctuation is a very common phenomenon in our daily life, which is rarely reported to be used for hydrogen production. Here we show a direct hydrogen evolution through harvesting cold-hot 298-323 K (25-50 °C) alternation energy in combination with the pyroelectric nanomaterial Ba0.7Sr0.3TiO3 (BST). The yield of hydrogen achieved 46.89μmol per gram of catalyst after 36 thermal cycles and the rate of hydrogen generation was up to 1.30 μmol/g per thermal cycle. The minimum of conduction band of BST is more negative than the conduction band level of H+/H2, enabling the reduction of water to form hydrogen. This efficient and eco-friendly pyro-catalytic method provides promising future of hydrogen evolution utilizing the natural cold-hot temperature fluctuation energy.
  • All-inorganic flexible piezoelectric energy harvester enabled by two-dimensional mica

    Nano Energy [43:351-358, 2018]
    A rapid surge in the research on self-powered bio-electronics is occurring toward the challenge that the state-of-the-art bio-devices require obsolete bulky batteries, which limit device miniaturization and lifespan. Among them, flexible piezoelectric materials that enable mechanical-to-electrical energy conversion, stimulate tremendous attraction to harvest mechanical energy from the motions of human and organs. Here, we report a cost-effective one-step process based on unique two-dimensional mica substrates to fabricate flexible piezoelectric energy harvesters, extending beyond prior art for all-inorganic flexible piezoelectric materials. As an exemplary demonstration, an all-inorganic, large scale, flexible piezoelectric Pb(Zr0.52Ti0.48)O3 energy harvester is fabricated with an outstanding performance (i.e., open-circuit voltage of 120 V, short-circuit current density of 150 μA cm-2 and power density of 42.7 mW cm-3), which are comparable to those via conventional “grow-transfer” technique from rigid substrates to organic soft ribbons, and are much greater by one to four orders of magnitude than previous reported ones based on piezoelectric nanofibers and organic thick films. In particular. This unique process provides a new perspective to fabricate all-inorganic piezoelectric energy harvesters for battery-free bio-electronics.
  • Phase transition in the near-surface region of ternary PIN-PMN-PT relaxor ferroelectric crystals

    Physics Review Applied [8:034032,2017]
    Relaxor ferroelectric single crystals have been documented to possess a skin effect in the near-surface region, which may play an important role in emerging micro-/nano-scale piezoelectric devices that are surface-dominated. Here, a metastable ferroelectric tetragonal phase is induced by an electric field applied above the Curie temperature (i.e., poling at high temperature) in rhombohedral structured PIN-PMN-PT ternary relaxor ferroelectric crystals. Most interestingly, this metastable tetragonal structure unexpectedly transforms into a monoclinic B-type (MB) phase, as revealed by reciprocal-space mesh scans via high-resolution x-ray diffraction. The domain configurations of the MB phase obtained by poling above the Curie temperature are similar to that obtained by poling at room temperature; however, the bulk piezoelectricity is extremely weak relative to that induced by the latter process. This controversy between microstructure and macro-property is understood by a “surface-interior” heterogeneous structure, which sheds insight into the existence of skin effects in the relaxor ferroelectric single crystals.
  • Flexible, Semitransparent, and Inorganic Resistive Memory based on BaTi0.95Co0.05O3 Film

    Advanced Materials (1700425,2017)
    Perovskite ceramics and single crystals are commonly hard and brittle due to their small maximum elastic strain. Here, large-scale BaTi0.95Co0.05O3 (BTCO) film with a SrRuO3 (SRO) buffered layer on a 10 μm thick mica substrate is flexible with a small bending radius of 1.4 mm and semitransparent for visible light at wavelengths of 500–800 nm. Mica/SRO/BTCO/Au cells show bipolar resistive switching and the high/low resistance ratio is up to 50. The resistive-switching properties show no obvious changes after the 2.2 mm radius memory being written/erased for 360 000 cycles nor after the memory being bent to 3 mm radius for 10 000 times. Most importantly, the memory works properly at 25–180 °C or after being annealed at 500 °C. The flexible and transparent oxide resistive memory has good prospects for application in smart wearable devices and flexible display screens.
  • Fragile MPB and phase stability in the near-surface region of relaxor ferroelectric crystals

    Physical Review B (94:174103, 2016, 14 pages)
    We have examined the effects of field cooling on the phase diagram of the relaxor system (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-xPT) for compositions near the morphotropic phase boundary (MPB). High-resolution diffraction measurements using Cu Kα x-rays, which probe ≈ 3 ?m below the crystal surface, were made on field-cooled (FC) single crystal specimens of PZN-4.5%PT and PZN-6.5%PT under electric fields of 1 kV/cm and 2 kV/cm applied along [001] and combined with previous neutron diffraction data, which probe the entire crystal volume for FC PZN-8%PT [Ohwada et al., Phys. Rev. B 67, 094111 (2003)]. A comparison to the zero-field-cooled (ZFC) PZN-xPT phase diagram reveals several interesting features: (1) the short-range monoclinic phase observed in the ZFC state on the low-PT side of the MPB is replaced by a monoclinic MA phase; (2) field cooling extends the tetragonal (T) phase to higher temperatures and lower-PT concentrations on field cooling; (3) the orthorhombic (O) phase near the MPB is replaced by a monoclinic MC phase; (4) the vertical MPB in the ZFC phase diagram bends significantly towards the low-PT side in the FC state.
  • Magnetoelectrics for Magnetic Sensor Applications: Status, Challenges and Perspectives

    Materials Today [Invited Review, 17(6):269, 2014]
    The magnetoelectric (ME) effect, with cross-correlation coupling between magnetic and electric degrees of freedom, is associated with two promising application scenarios: magnetic field sensors and electric-write magnetic-read memory devices. In this review, we highlight recent progress in ME laminates for sensor applications, in particular with regards to the most difficult technical obstacle to their practical use (i.e., reduction of equivalent magnetic noise), while presenting an evolution of ME materials. The challenges and perspectives for the technical obstacles that would enable ME composites for sensor applications are emphasized.
  • An extremely low equivalent magnetic noise (~pT Hz-1/2) magnetoelectric sensor

    Advanced Materials (23:4111, 2011)
    In this communication, we present the realization of extremely low equivalent magnetic noise in a Metglas/piezofiber heterosturcture sensor through a combination of giant ME effects and a reduction in each of the internal sensor noise sources. An extremely low equivalent magnetic noise of 5.1 pT Hz-1/2 was found at 1Hz, which is very close to the predicted value of 4.2 pT Hz-1/2. In particular, the equivalent magnetic noise of the ME sensor unit was as low as about 1 pT Hz-1/2 at a frequency of only several Hz. The structure is comprised of six-layers of magnetostrictive Metglas and a piezoelectric core composite consisting of five PMN-PT fibers interrogated by a pair of Kapton? interdigited (ID) electrodes

About Us

  • 教授,博士生导师;
  • 南京理工大学“青年拔尖人才”;
  • 江苏省“双创人才”;
  • 江苏省高等学校微课教学竞赛三等奖

Welcome to our group! We are a research group on Advanced Sensing Materials and Devices in the School of Materials Science and Engineering, established in 2015 after Prof. Yaojin  Wang joint Nanjing University of Science and Technology. In our group, we unite fundamental materials science and device technology, in particular focus on: 1) Magnetoelectric composites and heterostructural uncooled magnetic sensors; 3) Flexible ferro-electronics and multifunctional devices for sensor and energy conversion devices towards artificial intelligence and Internet of Things applications; 3) Piezo-electronics,devices and their underlying physics. The research in our group is highly interdisciplinary, so we welcome ambious students from the field of physics, material science and electrical engineering to join our group.  欢迎对科研充满激情、对未来充满梦想的你加入我们这个具有朝气的研究团队,共谋发展、共创辉煌!优秀学生提供美国Pennstate University和香港理工PolyU等联合培养或访问机会。

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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