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When a PhD student called Joseph Valasek discovered ferroelectricity exactly 100 years ago, few people realized the enormous impact it would have on science and technology. Amar S Bhalla and Avadh Saxena pick their favourite applications of this fundamental physics phenomenon

The year 2020 marks hundred years since the watershed discovery of the phenomenon of ferroelectricity although at that time its importance was hardly realized. We provide a historical account of th...

Optical properties of cobalt ferrite (CoFe2O4) nanoparticles are modeled and simulated employing finite element analysis (FEA) and density functional theory (DFT) for different particle sizes. The simulated absorption maxima of electronic excitations is red-shifted from 330 nm to 410 nm using finite element analysis and from 331.27 nm to 409.07 nm using quantum mechanical method, with increasing particle sizes from 40 nm to 50 nm. The measured absorption maxima matched the simulated results reasonably well and red-shifted to longer wavelengths from 315.59 nm to 426.73 nm with the increase in particle sizes from 30 nm to 50 nm. The DFT simulated, FEA simulated and experimentally derived optical band gap energies, Eg, were also acquired and compared. The simulated Eg values decreased from 3.228 to 2.478 eV and from 3.266 to 2.456 eV, while the experimental Eg value decreased from 3.473 to 2.697 eV, with increasing the particle sizes. The research demonstrated that the optical absorption of CoFe2O4 nanoparticles can be described with high accuracy using the quantum mechanical interpretation based on DFT. FEA based simulations have shown limitations for smaller (

Porous clay heterostructures (PCHs) have been developed for a decade now especially for adsorbent and catalytic support applications because of their high specific surface area with uniform small pore size. PCHs have been prepared through the surfactant-directed assembly of organosilicate in the galleries of montmorillonite (MMT), generally, single surfactant was applied. Challenge of using mixed surfactant template derived PCH is proposed to obtain higher surface area aiming for dielectric application. In this study, BC-PCH synthesized from mixed CTAB and CTAC surfactant systems was named and compared with B-PCH and C-PCH that synthesized from CTAB and CTAC surfactant system, respectively. The results revealed that the structure of MMT changed after modification and calcination process, as confirmed by Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD) analyses. Textural properties characterization showed that the BC-PCH samples exhibited higher specific surface area (SBET) 644–738 m2/g than that of B-PCH and C-PCH sample and slightly smaller pore size because the size of micelles in solution system from mixed surfactant decreases, which was confirmed by Dynamic Light Scattering analysis (DLS). Field Emission Scanning Electron Microscopy analysis (FE-SEM) illustrated the rough surface structure of mesoporous BC-PCH samples. The dielectric properties were measured by using the Inductance–Capacitance–Resistance meter (LCR). The dielectric constant (at 103 Hz) increased from 9 and 10 of single CTAB and CTAC surfactant template B-PCH and C-PCH to 15–17 of mixed surfactant series BC-PCHs, almost two-fold was obtained. The improvements of dielectric constant in BC-PCH samples are achieved by the increasing of interfacial polarization. Considering these results, BC-PCH materials can be further applied as candidates for an attractive filler to enhance the dielectric properties of polymer nanocomposite.

Electrochemical cells for direct conversion of solar energy to electricity (or hydrogen) are one of the most sustainable solutions to meet the increasing worldwide energy demands. In this report, a novel and highly-efficient ternary heterojunction-structured Bi4O7/Bi3.33(VO4)2O2/Bi46V8O89 photoelectrode is presented. It is demonstrated that the combination of an inversion layer, induced by holes (or electrons) at the interface of the semiconducting Bi3.33(VO4)2O2 and Bi46V8O89 components, and the rectifying contact between the Bi4O7 and Bi3.33(VO4)2O2 phases acting afterward as a conventional p–n junction, creates an adjustable virtual p–n–p or n–p–n junction due to self-polarization in the ion-conducting Bi46V8O89 constituent. This design approach led to anodic and cathodic photocurrent densities of + 38.41 mA cm–2 (+ 0.76 VRHE) and– 2.48 mA cm–2 (0 VRHE), respectively. Accordingly, first, this heterojunction can be used either as photoanode or as photocathode with great performance for artificial photosynthesis, noting, second, that the anodic response reveals exceptionally high: more than 300% superior to excellent values previously reported in the literature.

The complex permittivity of a multiphase aqueous solution is measured in the microwave frequency range of 2.8–6GHz using the cavity perturbation method for a temperature domain of −15 °C up to 0 °C...

3D printing is among the most exciting and rapidly advancing fields of research in materials engineering and device fabrication. The capability of developing a bottom-up approach to device fabricat...

Targeted drug delivery has become an increasingly popular field of research over the past decade as the desire for more discriminatory methods of treatment has risen. Photoacoustic-mediated...

Experiments to determine the effects of mechanical fastener induced pre-stress on a piezoelectric energy harvester (PEH) were conducted. Using a mechanical pre-stress fixture and an electro-dynamic...

This research is focused on piezoelectric energy harvesting at high pressure fields and low frequency applications. Lead Zirconate Titanate (PZT) is the primary piezoelectric evaluated with a focus...

In this study, (1-x)BaZr0.2Ti0.8O3-(x)(Ba0.7Ca0.3)0.985La0.01TiO3 ((1-x)BZT-(x)BCLT) ceramics, where x = 0.3, 0.4, 0.5, and 0.6, were prepared employing a conventional solid-state sintering technique. X-ray diffraction patterns and dielectric measurements indicated three phase regions at room temperature, including a single rhombohedral (x = 0.3), a phase coexistence of rhombohedral and tetragonal (x = 0.4), and a single tetragonal structure (x ≥ 0.5). X-ray photoemission spectra at the surface of ceramics confirmed the oxidation state of Ba2+, Ca2+, Ti4+, and Zr4+ ions. Upon BCLT addition, the reduction of the average grain size and the presence of the tetragonal structure significantly affected the dielectric, ferroelectric, and piezoelectric properties of these ceramics. With these results, the composition x = 0.3 showed maximum er′ and em′, whereas the composition x = 0.5 showed maximum Pr, Ec, d33, kp, and d∗33 factors. These results suggest a new phase diagram for the (1-x)BZT-(x)BCLT system, which could be tuneable by BCLT concentration and might be useful as an alternative material in dielectric, ferroelectric, and piezoelectric devices.

Made available in DSpace on 2019-10-06T15:53:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-01-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Ceramic composites based on Pb(Zr,Ti)O3/NiFe2O4 (PZT–NFO) have been synthesized from the conventional solid-state reaction method. The ferroelectric and magnetic properties have been investigated at room temperature. The obtained results revealed excellent characteristics of both ferroic responses, which suggest the studied ceramic composite as a promising material for practical applications in magneto-electric related devices. Grupo de Ferroelétricos e Materiais Multifuncionais Instituto de Física Universidade Federal de Uberlândia Departamento de Física e Química UNESP Instituto Federal de Educação Ciência e Tecnologia do Triangulo Mineiro Departamento de Física Universidade Federal de São Carlos Inamori School of Engineering Alfred University Multifunctional Electronic Materials and Devices Research Lab Department of Electrical and Computer Engineering College of Engineering The University of Texas at San Antonio Departamento de Física e Química UNESP

In this work we present a methodology that combines the Rietveld structure refinement and the Maximum Entropy Method (MEM) to analyze the crystal and electronic structures, and the chemical...

In this work, we have studied the microscopic, ferroelectric, magnetic and microstructural characteristics of cobalt ferrite/barium titanate core–shell magnetoelectric nanocomposites. Magnetoelectr...

Piezoelectric materials have widely been used for applications in microelectromechanical systems, electromechanical devices, civil infrastructure, in transportation and smart devices. The p...

An atomistic field theory was introduced to study the electromechanical response in a ferroelectric perovskite at nanoscale. Based on a shell model potential, the polarization switching pro...

The dynamic modulation of effective electro-optic (EO) coefficient in pulsed laser deposited SBN thin film was investigated using Senarmont Compensation method. Prism coupling technique was used to realize a waveguide to guide the light in SBN thin film. The dynamic variation of effective electro-optic coefficient over a wide frequency range (10 Hz–20 MHz) was investigated with the maximum value of 198 pm/V. This wide frequency bandwidth obtained in the present article opens up avenues to design an EO modulator using ferroelectric SBN thin film. A lower value of half wave voltage (38 V) along with high figure of merit ( 0.9 × 10 6 V 2 ) were obtained for the fabricated SBN60 thin film based EO modulator.

Optical techniques offer a practical approach to characterize fluid dynamics due to the complicated nature of the mathematical equations that describe turbulent flows. However, experimental setups such as particle image velocimetry are often restricted to studies with steady flows moving through channels with clear walls to detect the signals from lasers using optical receivers and particles that reflect light. For non-isothermal unsteady flows in scraped surface crystallazers, the signal detecting process is not trivial due to the interference caused by the rotating shaft and the scraper blades that homogenize the solution in the mixing chamber. Also, the cooling jacket installed on the periphery of the agitator obstructs the field of view impeding the study of the interrogation region. The goal of this investigation was to determine the phase-transition temperature of a multi-phase unsteady flow in a scraped surface crystallizer using optical spectroscopy in the UV-VIS range. Temperature, pressure, and spectroscopy measurements were measured in-situ to characterize the mixture by its physical properties to obtain a correlation between the optical signatures before and after the glass-transition temperature. Results showed that optical absorbance successfully detected the physical variations in the phase- transition process of the unsteady flow.

The primary focus of this research is on the application and optimization of direct piezoelectric effect in energy harvesting from low frequency mechanical vibrations such as from roadway t...

Multiferroic materials with magnetoelectric properties, due to their coupling between the electrical and magnetic properties have attracted the attention of many researchers. Perovskite structured materials based on BiFeO3 are a class of materials largely considered in these studies. In this work, Bi1-xNdxFe0.99Co0.01O3 (x = 0.05, 0.10 and 0.20) compositions were synthesized aiming a better understanding of the crystal and electronic structure role in ferroic properties of these materials. Structural studies were made by X-ray diffraction and Rietveld refinement; evidencing the rhombohedral symmetry of the samples with space group R3c. Electron density calculations were performed by the maximum entropy method. These studies showed that Nd3+ substitution causes distortions in the unit cell, which have influence on the magnetic properties. Also, the electron density maps showed the bonds between the iron and oxygen ions did not changed a lot. But the Minimum Electron Density observations were enough...

The magnetoelectric materials have been being studied due to the scientific chalenges and the very promissing possibility of applications in electronic devices. BiFeO3 is room temperature single-phase multiferroic material. However there are some issues regarding conductivity and undesired parasitic phases that cause the experimentally reduced electrical polarization and low or no net magnetization in this material. In order to solve these questions we studied the effect of partial replacement of Bi3+ by Nd3+ in the Bi1-xNdxFe0.99Co0.01O3 compositions. X-ray diffraction patterns confirmed single phased rhombohedrally distorted perovskite structure in obtained ceramics. Scanning electron microscopy images reveal that the ceramic grains are almost irregular spheres with a 2 μm in diameter, and samples present equal porosity. With the increasing of the Nd3+ substitution the real part of the dielectric constant increased in almost 10 times but decreases the magnetization. As a consequence, the Bi1-xNd...

The temperature dependence of the dielectric properties, along with the field and frequency dependences of the magnetoelectric properties of a CoFe2O4/Pb(ZrxTi1-x)O3/CoFe2O4 laminate structure has ...

Core-shell magnetoelectric nanocomposite, comprising of spinel cobalt ferrite (CoFe2O4) core and perovskites barium titanate (BaTiO3) shell prepared by hydrothermal method have been reporte...

In this work, we reported investigations on the structural, magnetic and dielectric properties of Mn doped 0.9BiFeO3-0.1BaTiO3 multiferroic compounds. X-ray diffraction studies revealed that the materials crystallized in a pure distorted rhombohedral perovskite structure. A significant magnetization increase (reaching 0.50 emu/g) was observed for Mn - doped samples. The dielectric characterization revealed that for the un-doped sample two conductivity mechanisms are present, one starting around 177 K and other around 325 K. In the doped samples, however, one of these mechanisms was suppressed increasing the resistivity and decreasing the dielectric losses of the samples.

The structural, dielectric, ferroelectric, and ferromagnetic properties of multiferroic ceramics (1–x)Ba(Zr0.2Ti0.8)O3-xBa0.7Ca0.3FeTaO5 (abbreviated as (1–x)BZT-xBCFT where x = 0.2, 0.25, ...

In this manuscript, microstructural, structural and magnetic properties of pure and La doped (0.6)BiFeO3-(0.4)PbTiO3 polycrystals were investigated. X-ray diffraction, transmission and scan...

Nanoscale structural and polar behavior in abalone and clamshell have been studied using the scanning probe techniques. Untreated pristine sample surfaces were probed to realize their intrinsic ele...

Made available in DSpace on 2019-10-04T12:35:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-01-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) Abdus Salam International Centre for Theoretical Physics, Trieste, Italy Barium titanate (BaTiO3) ceramics, prepared by the Pechini's method, were investigated considering the influence of the samarium-modifier concentration. Nanosized crystallites in the order of 15-20nm have been successfully obtained by this synthesis process. The structural properties analyzed from the X-ray diffraction technique, confirmed a single ferroelectric phase with no additional secondary-phases, and suggest the amphoteric character (A- or B-site occupancy) of the Sm3+ ion into the BaTiO3 structure. This effect, which has not been previously reported, has been also confirmed from microstructural (scanning electron microscopy) analysis. The obtained results reveal to be the starting point for further detailed investigations of the real amphoteric behavior of the Sm3+ ion, and other rare-earth elements in perovskite-type structure systems. Univ Fed Uberlandia, Inst Fis, Grp Ferroeletr & Mat Multifuncionais, Uberlandia, MG, Brazil Univ Estadual Paulista, Dept Fis & Quim, Ilha Solteira, SP, Brazil Univ La Habana, Fac Fis, Inst Ciencia & Tecnol Mat, Havana, Cuba Univ Sao Paulo, IFSC, Grp Nanomat & Ceram Avancadas, Sao Carlos, SP, Brazil Univ Texas San Antonio, Coll Engn, Dept Elect & Comp Engn, Multifunct Elect Mat & Devices Res Lab, San Antonio, TX USA Univ Estadual Paulista, Dept Fis & Quim, Ilha Solteira, SP, Brazil

(Ba0.7Ca0.3)Ti1-xCuxO3-x ceramics (where x = 0, 0.01, 0.02 and 0.03) were prepared employing a conventional solid state sintering technique. X-ray diffraction patterns and Ti K-edge X-ray Absorption Near-Edge Structure (XANES) spectra indicated a structural distortion of Cu-doped ceramics. Depending on Cu content, the features of normal ferroelectric and diffuse dielectric phase transition could be induced by the Cu addition. The temperature where maximum dielectric existed was decreased upon increase of Cu concentration. The creation of oxygen vacancies and defect dipoles caused double-like P-E loop in host material. The decrease of d33, g33 and kp values was observed in correlation with decrease of Pr in doped ceramics. The results here suggested that the electrical properties of this ceramic system may be largely tunable by Cu dopant and could be an attractive material for high-dielectric response devices.

Bi2(Zn1/3Nb2/3)2O7 ceramics were synthesized using conventional solid-state reaction. The effect of densification annealing treatments on microstructures and microwave dielectric properties of Bi2(Zn1/3Nb2/3)2O7 ceramics have been investigated. The ordered of B-site zirconolite structures were obtained after a long-time annealing. The order-disorder transition contributes to enhance the microwave dielectric properties of Bi2(Zn1/3Nb2/3)2O7 ceramics. The ceramics sintered at 980 °C exhibit a large permittivity of 75 and a Qf value of 3000 GHz. The most efficient annealing treatment which induced a≈100% improvement of Qf value was obtained in the samples annealed at 890 °C for 24 h, while the permittivity remain stable. As the annealing temperature increased to 930 °C, the Qf value abruptly decreased. The microwave dielectric properties of Bi2(Zn1/3Nb2/3)2O7 ceramics are affected by the enhancement of cation order and the reduction of crystal defect. An excellent microwave dielectric properties Qf ≈ 6300 GHz, e ≈ 76 and τf ≈ 189 ppm/°C was obtained when the ceramic was annealed at 890 °C for 24 h.

Electro-optic (EO) devices with high EO coefficients at radio and microwave frequencies are integral components of the photonics industry. This work determines the EO effect of ferroelectric Li-doped niobium-rich potassium tantalate niobate (K 0.95 Li 0.05 Ta 1- x Nb x O 3 ; KLTN) single crystals using improved dynamic EO measurement. The phase transitions of KLTN crystals were investigated via variable-temperature Raman spectroscopy. A full view of the surface displacement and velocity for the KLTN sample at the resonant frequency was studied using an ultra-frequency vibrometer. The KLTN sample with x = 0.60 exhibits the enhanced effective EO coefficient (γ c ) ∼ 217 pm/V near the piezoelectric resonant peaks, which is comparable with the value at low frequency. The piezoelectric enhanced EO property of KLTN single crystals can be attributed to nonlinear polarization and nonzero stress, and showing promising for designing practical optical-piezoelectric-mechanism coupling devices.