scholarly journals Improper molecular ferroelectrics with simultaneous ultrahigh pyroelectricity and figures of merit

2021 ◽  
Vol 7 (5) ◽  
pp. eabe3068
Author(s):  
Wenru Li ◽  
Gang Tang ◽  
Guangzu Zhang ◽  
Hasnain Mehdi Jafri ◽  
Jun Zhou ◽  
...  
Keyword(s):  
First Principles ◽  
High Performance ◽  
Rotation Angle ◽  
Pyroelectric Coefficient ◽  
Ferroelectric Materials ◽  
Dielectric Constants ◽  
Great Promise ◽  
Figures Of Merit ◽  
Order Of Magnitude ◽  
High Dielectric

Although ferroelectric materials exhibit large pyroelectric coefficients, their pyroelectric figures of merit (FOMs) are severely limited by their high dielectric constants because of the inverse relationship between FOMs and dielectric constant. Here, we report the molecular ferroelectric [Hdabco]ClO4 and [Hdabco]BF4 (dabco = diazabicyclo[2.2.2]octane) exhibiting improper ferroelectric behavior and pyroelectric FOMs outperforming the current ferroelectrics. Concurrently, the improper molecular ferroelectrics have pyroelectric coefficients that are more than one order of magnitude greater than the state-of-the-art pyroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3. Our first-principles and thermodynamic calculations show that the strong coupling between the order parameters, i.e., the rotation angle of anions and polarization, is responsible for the colossal pyroelectric coefficient of the molecular ferroelectrics. Along with the facile preparation and self-poling features, the improper molecular ferroelectrics hold great promise for high-performance pyroelectric devices.

scholarly journals Effects of Oxygen Ion Irradiation on PZT Modified Ferroelectric Materials for Space Applications

2016 ◽  
Vol 1 (1) ◽  
Keyword(s):  
Dielectric Constant ◽  
Ion Irradiation ◽  
Heavy Ion ◽  
Ferroelectric Material ◽  
Pyroelectric Coefficient ◽  
Ferroelectric Materials ◽  
Dielectric Constants ◽  
Space Applications ◽  
Oxygen Ion ◽  
Wide Range

Lead magnesium niobate-lead titanate (PMN-PT) is an important and high performance piezoelectric and pyroelectric relaxor material having wide range of applications in infrared sensor devices. Present work studies the fabrication and dielectric characteristics of PMN-PT in the bulk form. The PMN-PT bulk material was prepared in sol-gel method and subsequently irradiated with heavy ion oxygen. The materials were analyzed and determined that the relaxor ferroelectric material indicated changes in its dielectric constant and pyroelectric coefficient after irradiation. Due to the radiation fluent of 1×1016 ions/cm2 , the dielectric constant of the material increased uniformly, while its pyroelectric coefficient showed a sharp increased to the value of 5×10-9 μC/cm2 °C with increase in temperature. Its dielectric constants showed increase in values of 527 μC/cm2 °C at 50°C, 635 μC/ cm2 °C at 60°C and 748 μC/cm2 °C at 70°C. Properties such as the material impedance, admittance and modulus were investigated for changes in properties which became evident after irradiation. In this paper effect of oxygen ion irradiation on the LiTaO3 and two commercial samples BM 300 and BM 941 are also reported and analyzed. All these bulk materials were functional even after irradiation and was showing enhancement in some of the key characteristics of ferroelectric material.

scholarly journals Development of High Dielectric Electrostrictive PVDF Terpolymer Blends for Enhanced Electromechanical Properties

Nanomaterials ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 6
Author(s):  
Il Jin Kim ◽  
Kie Yong Cho ◽  
Eunji Kim ◽  
Young Je Kwon ◽  
Min Young Shon ◽  
...  
Keyword(s):  
High Performance ◽  
Vinylidene Fluoride ◽  
Electrical Breakdown ◽  
Electrostatic Force ◽  
Electroactive Polymers ◽  
Dielectric Constants ◽  
Transverse Strain ◽  
Electromechanical Properties ◽  
Organic System ◽  
High Dielectric

Electroactive polymers with high dielectric constants and low moduli can offer fast responses and large electromechanical strain under a relatively low electric field with regard to theoretical driving forces of electrostriction and electrostatic force. However, the conventional electroactive polymers, including silicone rubbers and acrylic polymers, have shown low dielectric constants (ca. < 4) because of their intrinsic limitation, although they have lower moduli (ca. < 1 MPa) than inorganics. To this end, we proposed the high dielectric PVDF terpolymer blends (PVTC-PTM) including poly(vinylidene fluoride-trifluoroethylene-chlorofluoro-ethylene) (P(VDF-TrFE-CFE), PVTC) as a matrix and micelle structured poly(3-hexylthiophene)-b-poly(methyl methacrylate) (P3HT-b-PMMA, PTM) as a conducting filler. The dielectric constant of PVTC-PTM dramatically increased up to 116.8 at 100 Hz despite adding only 2 wt% of the polymer-type filler (PTM). The compatibility and crystalline properties of the PVTC-PTM blends were examined by microscopic, thermal, and X-ray studies. The PVTC-PTM showed more compatible blends than those of the P3HT homopolymer filler (PT) and led to higher crystallinity and smaller crystal grain size relative to those of neat PVTC and PVTC with the PT filler (PVTC-PT). Those by the PVTC-PTM blends can beneficially affect the high-performance electromechanical properties compared to those by the neat PVTC and the PVTC-PT blend. The electromechanical strain of the PVTC-PTM with 2 wt% PTM (PVTC-PTM2) showed ca. 2-fold enhancement (0.44% transverse strain at 30 Vpp μm−1) relative to that of PVTC. We found that the more significant electromechanical performance of the PVTC-PTM blend than the PVTC was predominantly due to the electrostrictive force rather than electrostatic force. We believe that the acquired PVTC-PTM blends are great candidates to achieve the high-performance electromechanical strain and take all benefits derived from the all-organic system, including high electrical breakdown strength, processibility, dielectrics, and large strain, which are largely different from the organic–inorganic hybrid nanocomposite systems.

Application study of Mn-doped PIN-PMN-PT relaxor ferroelectric crystal grown by Vertical Gradient Freeze method

2020 ◽  
Vol 557 (1) ◽  
pp. 9-17 ◽  
Author(s):  
Zibo Jiang ◽  
Zuo-Guang Ye
Keyword(s):  
High Performance ◽  
Electromechanical Coupling ◽  
Strong Electric Field ◽  
Vertical Gradient ◽  
Pyroelectric Coefficient ◽  
Relaxor Ferroelectric ◽  
Dielectric Constants ◽  
Coupling Coefficients ◽  
Ferroelectric Crystal ◽  
Vertical Gradient Freeze

A 3-inch Mn:PIN-36%PMN-32%PT (Generation III) relaxor ferroelectric crystal was grown using the Vertical Gradient Freeze method. Crystals of [1, 11] and [111] orientations were prepared and studied, evaluating their dielectric constants, piezoelectric coefficients, electromechanical coupling coefficients, loss tangents and pyroelectric coefficients. It is shown that in pyroelectric applications, [111]-poled crystals are particularly suitable for high performance sensors due to a relatively high pyroelectric coefficient, low loss tangent. In addition, the specific heat is lower as compared to LiTaO3. It is also shown that the alternating current (AC) poling has a more significant effect on the [001]-poled crystal than on the [011]- and [111]-poled crystals due to the lattice distortion induced by a strong electric field along the [001] direction.

scholarly journals Physical aspects of 0-3 dielectric composites

2015 ◽  
Vol 05 (02) ◽  
pp. 1550012 ◽  
Author(s):  
Lin Zhang ◽  
Patrick Bass ◽  
Z.-Y. Cheng
Keyword(s):  
Dielectric Properties ◽  
High Performance ◽  
Critical Role ◽  
Practical Importance ◽  
Dielectric Constants ◽  
Challenging Problem ◽  
New Developments ◽  
High Dielectric ◽  
Made In

0-3 dielectric composites with high dielectric constants have received great interest for various technological applications. Great achievements have been made in the development of high performance of 0-3 composites, which can be classified into dielectric–dielectric (DDCs) and conductor–dielectric composites (CDCs). However, predicting the dielectric properties of a composite is still a challenging problem of both theoretical and practical importance. Here, the physical aspects of 0-3 dielectric composites are reviewed. The limitation of current understanding and new developments in the physics of dielectric properties for dielectric composites are discussed. It is indicated that the current models cannot explain well the physical aspects for the dielectric properties of 0-3 dielectric composites. For the CDCs, experimental results show that there is a need to find new equations/models to predict the percolative behavior incorporating more parameters to describe the behavior of these materials. For the DDCs, it is indicated that the dielectric loss of each constituent has to be considered, and that it plays a critical role in the determination of the dielectric response of these types of composites. The differences in the loss of the constituents can result in a higher dielectric constant than both of the constituents combined, which breaks the Wiener limits.

Electron microscopy studies of PZT ferroelectric film capacitor structures

1992 ◽  
Vol 50 (2) ◽  
pp. 1364-1365
Author(s):  
V. Kaushik ◽  
P. Maniar ◽  
J. Olowolafe ◽  
R. Jones ◽  
A. Campbell ◽  
...  
Keyword(s):  
Electric Fields ◽  
Sol Gel ◽  
Ferroelectric Material ◽  
Dielectric Constants ◽  
Dielectric Films ◽  
Lead Zirconium Titanate ◽  
Si Substrate ◽  
Film Capacitor ◽  
Pzt Films ◽  
High Dielectric

Lead zirconium titanate films (Pb (Zr,Ti) O3 or PZT) are being considered for potential application as dielectric films in memory technology due to their high dielectric constants. PZT is a ferroelectric material which shows spontaneous polarizability, reversible under applied electric fields. We report herein some results of TEM studies on thin film capacitor structures containing PZT films with platinum-titanium electrodes.The wafers had a stacked structure consisting of PZT/Pt/Ti/SiO2/Si substrate as shown in Figure 1. Platinum acts as electrode material and titanium is used to overcome the problem of platinum adhesion to the oxide layer. The PZT (0/20/80) films were deposited using a sol-gel method and the structure was annealed at 650°C and 800°C for 30 min in an oxygen ambient. XTEM imaging was done at 200KV with the electron beam parallel to <110> zone axis of silicon.Figure 2 shows the PZT and Pt layers only, since the structure had a tendency to peel off at the Ti-Pt interface during TEM sample preparation.

The need of electron microscopy in the study of domains and domain walls in ferroelectrics

1994 ◽  
Vol 52 ◽  
pp. 550-551
Author(s):  
Wenwu Cao
Keyword(s):  
Domain Wall ◽  
Domain Walls ◽  
High Mobility ◽  
Continuum Theory ◽  
Polarization Vector ◽  
Ferroelectric Materials ◽  
Dielectric Constants ◽  
Nonlocal Coupling ◽  
Cubic Symmetry ◽  
Gradient Energy

Domain structures play a key role in determining the physical properties of ferroelectric materials. The formation of these ferroelectric domains and domain walls are determined by the intrinsic nonlinearity and the nonlocal coupling of the polarization. Analogous to soliton excitations, domain walls can have high mobility when the domain wall energy is high. The domain wall can be describes by a continuum theory owning to the long range nature of the dipole-dipole interactions in ferroelectrics. The simplest form for the Landau energy is the so called ϕ model which can be used to describe a second order phase transition from a cubic prototype,where Pi (i =1, 2, 3) are the components of polarization vector, α's are the linear and nonlinear dielectric constants. In order to take into account the nonlocal coupling, a gradient energy should be included, for cubic symmetry the gradient energy is given by,

Proteins and direct methods

1991 ◽  
Vol 197 (3-4) ◽  
Author(s):  
Fan Hai-fu ◽  
Hao Quan ◽  
M. M. Woolfson
Keyword(s):  
First Principles ◽  
Figure Of Merit ◽  
Direct Methods ◽  
Large Structure ◽  
Low Resolution ◽  
Figures Of Merit ◽  
Large Structures ◽  
Resolution Data

AbstractConventional direct methods, which work so well for small structures, are less successful for macromolecules. Where it has been demonstrated that a solution might be found using direct methods it is then found that the usual figures of merit are unable to distinguish the few good sets of phases from the large number of sets generated. The reasons for the difficulties with very large structures are considered from a first-principles approach taking into account both the factors of having a large number of atoms and low resolution data. A proposal is made for trying to recognize good phase sets by taking a large structure as a sum of a number of smaller structures for each of which a conventional figure of merit can be applied.

scholarly journals Electrocaloric effect in ferroelectric materials: from phase field to first-principles based effective Hamiltonian modeling

2021 ◽  
pp. 100050
Author(s):  
Jingtong Zhang ◽  
Xu Hou ◽  
Yajun Zhang ◽  
Gang Tang ◽  
Jie Wang
Keyword(s):  
Phase Field ◽  
First Principles ◽  
Ferroelectric Materials ◽  
Effective Hamiltonian ◽  
Electrocaloric Effect

scholarly journals Electronic and optical properties of vacancy ordered double perovskites A2BX6 (A = Rb, Cs; B = Sn, Pd, Pt; and X = Cl, Br, I): a first principles study

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Muhammad Faizan ◽  
K. C. Bhamu ◽  
Ghulam Murtaza ◽  
Xin He ◽  
Neeraj Kulhari ◽  
...  
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
First Principles ◽  
Density Functional ◽  
Perovskite Solar Cells ◽  
Dielectric Constants ◽  
Maximum Efficiency ◽  
Exchange Potential ◽  
Double Perovskites ◽  
Electronic And Optical Properties

AbstractThe highly successful PBE functional and the modified Becke–Johnson exchange potential were used to calculate the structural, electronic, and optical properties of the vacancy-ordered double perovskites A2BX6 (A = Rb, Cs; B = Sn, Pd, Pt; X = Cl, Br, and I) using the density functional theory, a first principles approach. The convex hull approach was used to check the thermodynamic stability of the compounds. The calculated parameters (lattice constants, band gap, and bond lengths) are in tune with the available experimental and theoretical results. The compounds, Rb2PdBr6 and Cs2PtI6, exhibit band gaps within the optimal range of 0.9–1.6 eV, required for the single-junction photovoltaic applications. The photovoltaic efficiency of the studied materials was assessed using the spectroscopic-limited-maximum-efficiency (SLME) metric as well as the optical properties. The ideal band gap, high dielectric constants, and optimum light absorption of these perovskites make them suitable for high performance single and multi-junction perovskite solar cells.

scholarly journals Particle Size Effect of Lanthanum-Modified Bismuth Titanate Ceramics on Ferroelectric Effect for Energy Harvesting

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Sangmo Kim ◽  
Thi My Huyen Nguyen ◽  
Rui He ◽  
Chung Wung Bark
Keyword(s):  
Particle Size ◽  
Energy Harvesting ◽  
High Speed ◽  
High Performance ◽  
Bismuth Titanate ◽  
Vinylidene Fluoride ◽  
Piezoelectric Materials ◽  
Renewable Energy Sources ◽  
Particle Size Effect ◽  
Ferroelectric Materials

AbstractPiezoelectric nanogenerators (PNGs) have been studied as renewable energy sources. PNGs consisting of organic piezoelectric materials such as poly(vinylidene fluoride) (PVDF) containing oxide complex powder have attracted much attention for their stretchable and high-performance energy conversion. In this study, we prepared a PNG combined with PVDF and lanthanum-modified bismuth titanate (Bi4−XLaXTi3O12, BLT) ceramics as representative ferroelectric materials. The inserted BLT powder was treated by high-speed ball milling and its particle size reduced to the nanoscale. We also investigated the effect of particle size on the energy-harvesting performance of PNG without polling. As a result, nano-sized powder has a much larger surface area than micro-sized powder and is uniformly distributed inside the PNG. Moreover, nano-sized powder-mixed PNG generated higher power energy (> 4 times) than the PNG inserted micro-sized powder.

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