AbstractThe demand to produce clean energy has been increasing over the last years due to the various climate changes, which are strongly afflicting the world. Therefore, it is necessary to implement new and alternative energy sources that contribute for the environment preservation. That is the case, for instance, of novel energy-storage devices, which could contribute for the current demand of clean energies. In fact, most of the system used nowadays are those lead-based materials, which are strongly pollutant and contribute for the environment contamination. In this way, the interest in the development and study of lead-free materials has become a real priority in the scientific community. The objective of the present work is to synthesize and investigate the physical properties of lead-free ferroelectric systems based on BaTiO3 (BT) with technological interest. In particular, the structural and dielectric properties have been investigated as a function of the Sn4+ content, used as a doping element in the BT hosting crystalline structure. The phase transition characteristics have been also analyzed in a wide temperature and frequency range.

AbstractGenerally speaking, the aerodynamic force generated by each component will hinder the endurance and performance of the UAV. In addition, because PVDF has the characteristics of high flexibility, corrosion resistance and nontoxic, a wind resistance pro-filed sensor based on polyvinylidene fluoride (PVDF) is developed, which can be used to measure the resistance of UAV in different directions. The sensor consists of nine surfaces, which can measure the resistance caused by wind in different directions at the same time. By analyzing the average output voltage collected under different wind speeds and flight states, the resistance of different UAV propellers is estimated. This research is helpful to improve the structure of UAV, reduce the impact of drag, and increase the UAV's endurance time and carrying capacity.

AbstractLead-free AgNbO3 ceramic system has been synthesized via solid-state reaction sintering method. High-density material has been obtained, revealing the formation of the pure perovskite structure, without secondary phases. Dielectric response showed three typical anomalies in the temperature dependence of the dielectric permittivity, with evident frequency-dependent dielectric dispersion for temperatures close to both the room temperature and the Curie temperature regions. Results have been analyzed and discussed within the framework of the theoretical models reported in the literature.

AbstractPVDF-based compounds are one of the most promising materials for technological application. In this work, structural and optical techniques have been used to study PVDF-based lead-free ceramic composites, considering the inclusion of the ferroelectric BaTiO3 (BT) and magnetic BaFe12O19 (BHF) and SrFe12O19 (SHF) phases. Results obtained from X-Ray diffraction measurements revealed the formation of the PVDF/ceramic composites with the respective ferroelectric and magnetic phases related to the BT and BHF and SHF ceramics. On the other hand, from the analyses of the Raman and FT-IR spectroscopies, it was possible to confirm the incorporation of the ceramics into the PVDF matrix. It was observed that the β-phase % decreased with the increase of doping content, except for the PVDF/BHF composite, which showed to remains almost constant. The results reveal that the studied hybrid PVDF/ceramic samples could be considered potential candidates for electronic applications.

AbstractWe report on magneto-electric (ME) effects in core-shell nanofibers of hexagonal ferrites and ferroelectrics synthesized by electrospinning. The core-shell structure in annealed fibers of M, Y, and W-type hexagonal ferrites and PZT was confirmed by electron and scanning microwave microscopy. Fibers showed ferroelectric polarization and magnetization smaller than for bulk samples. The ME coupling strength was measured by magnetic field H induced polarization and ME voltage coefficient (MEVC). In SrM-PZT fibers the remnant polarization decreased by as much as 20% with the application of H. The highest MEVC was measured for magnetic field assembled films of SrM–PZT fibers.

AbstractPure Li2MnO3 powders were synthesized at 900 °C for 4 h by a solid-state reaction method. Li2MnO3 ceramics were prepared in the temperature range of 1100 °C to 1250 °C. All the samples displayed a single phase structure. The microwave dielectric properties of sintered samples were closely related to sintering temperature and microstructure. The Li2MnO3 ceramics exhibited a well microwave dielectric properties of εr = 12.5, Q × f = 43150 GHz, τf = −9.5 ppm/°C at 1200 °C.

AbstractThe Sn-doped CuO nanosheets were synthesized on the surface of ZnO nanorods arrays by a two-step method. The as-prepared samples were investigated by X-ray diffraction (XRD), electron microscopy techniques (SEM and EDS), X-ray photoelectron spectroscopy (XPS), UV–Vis spectroscopy, and evaluation of photoelectric performances. With the increase of [Sn4+]/[Cu2+] concentration ratio, the size and number of CuO nanosheets coated on the surface of ZnO nanorods become smaller, and the surface of ZnO nanorods become more and more rough. When the [Sn4+]/[Cu2+] concentration ratio is 2%, the dark current, photocurrent and photoelectric sensitivity of the prepared Sn-doped CuO@ZnO nanorod arrays composites photoelectric devices are 0.038 µA, 141.52 µA and 3724.2, respectively. In this sense, probing the Sn modified CuO@ZnO nanorod arrays composites can elucidate some useful keys for the development of high photoelectric properties.

AbstractZn-doped and un-doped BCTO ceramics (Bi2/3Cu3−xZnxTi4O12, x = 0 and 0.05) were prepared by chemical route sintered at 1123 K for 8 h. The Phase formation of ceramics were confirmed by X-ray Diffraction. Their microstructural properties were examined through SEM, EDX, and TEM. The dielectric constant (ɛr) of BCTO ceramic was obtained higher than BCZTO-0.05 ceramics at 100 Hz and 470 K. The tangent loss (tan δ δ δ) value for Zn doped BCTO ceramics were found to be lower than undoped BCTO ceramics at 10 kHz and 310 K. The conductivity dependence of Bi2/3Cu3−xZnxTi4O12 ceramics (where x = 0, 0.05), with the inverse of temperature follows the Arhenius equation, with a major temperature range of 300–500 K.

AbstractWe used the density functional theory with spin polarization to investigate multifunctional properties of the Sm-doped BaTiO3 system (Ba1–xSmxTiO3). The self-consistent calculation results were used to analyze the ferromagnetic and dielectric properties. The spontaneous electric polarization was estimated from the King-Smith and Vanderbilt theory and 1s core-hole absorbing atom was used to calculate the oxygen K-edge XANES spectra. The Hubbard correction has been considered over the rare-earth f-electrons. Results for x = 0.125 revealed a narrow band-gap energy, showing an enhanced ferroelectric character, with a spontaneous polarization higher than the reported for the pure tetragonal BaTiO3. On the other hand, the magnetic properties have been also confirmed, with a total magnetization value around 5.90 µB/cell, which have been mainly ascribed to the inclusion of the Sm cation into the BT crystalline structure.

AbstractRecent developments in Machine Learning (ML) models that purport to automate material discovery are explored, with a treatment of the logical extension of this work that we have defined as “Design Discovery”. If we use the Rydberg sensor as a representative target for modeling with advanced ML tools and algorithms, the definition of a sufficient feature set to establish an ML model requires the quantum mechanical description of electrical and magnetic interactions that leverage Stark effect observations and Rydberg states of the targeted atom, as well as other forces internal and external to the atomic structure. This provides a feature rich environment from the standpoint of predictive design using Machine Learning models. The paper concludes with a theoretical treatment of a Rydberg sensor and its potential sensitivity to measurement of extremely small electromagnetic phenomena, with an initial consideration of potential variations of existing experiments that can be “discovered” from an appropriately defined ML design discovery model.

AbstractA comparison study of pure barium titanate BaTiO3, dipole-pair [Ga3+, Ta5+] substituted barium titanate Ba(Ga3+, Ta5+)0.005Ti0.99O3 ([Ga3+, Ta5+]: BaTiO3), single ion [Ga3+] substituted barium titanate Ba(Ga3+)0.01Ti0.99O3 ([Ga3+]: BaTiO3), and single ion [Ta5+] substituted barium titanate Ba(Ta5+)0.01Ti0.99O3 ([Ta5+]: BaTiO3) ferroelectric ceramics have been conducted in order to discern the unique electric and dielectric properties derived from dipole-pair substitution. The band gap, DC resistivity, relative permittivity, dissipation factor, and complex impedance have been measured and analyzed. The dipole-pair substituted material is demonstrated to be an excellent dielectric, which possesses high electrical resistivity, high activation energy, significant dielectric diffuseness, high relative permittivity and low dissipation factor, due to charge compensation and creation of dipole-pairs in barium titanate solid solution ceramic matrix. The single substituted (acceptor and donor, respectively) samples behave more like traditional semiconductors, which have lower electrical resistivity, lower activation energy, and exhibit strong dielectric anomaly and large dissipation factor due to charge imbalance (electrons and holes) in part compensated for through additional defect creation. The relaxor-like behavior of the dipole-pair substituted sample is distinguishable from the classic relaxor through electric properties and structural phase diagram and is anticipated to spark more attention and further exploration. The unique features of electric resistivity and dielectric diffuseness of the dipolar-pair engineered BaTiO3 affords opportunity for designing properties of novel relaxor-like ferroelectrics.

AbstractImpulse excitation is a suitable tool to determine the temperature dependence of Young’s modulus and to monitor the ferroelectric phase transition of unpoled barium titanate ceramics (tetragonal-to-cubic and vice versa). By measurement from room temperature to 200–300 °C and back, it is found that there is an elastic anomaly with a sharp minimum (at 120 °C during heating and 110 °C during cooling, with a completely reproducible hysteresis), below and above which Young’s modulus exhibits values of 40–50 GPa and up to 90 GPa, respectively, and damping changes abruptly from values of order 0.01 to less than 0.001.

AbstractThe sensitivity analysis of the anisotropic properties for PZT-4 and PZT-5 have been performed using the complex variable finite element method (ZFEM) on a two-dimensional geometry. A thin film model is subjected to a uniform boundary load to induce mechanical strain yielding variations in the electric potential field. The numerical results from mechanical displacements and electric potential fields are verified against the solution from a commercial software. The first order derivatives obtained from ZFEM illustrate the sensitivity of material properties as design parameters for real time tunability of additive manufacturing processes. Results show that the largest sensitivities for the direct piezoelectric effect emerge from C33 and the elastic anisotropic coupling of normal and shear stresses through coefficient C13 followed by the dielectric and piezoelectric constants in the poling direction.

AbstractThe non-linear behavior of a broadband piezoelectric energy harvester with various configurations (single-layer, multi-layer and multi-step) in multimode operation is designed for powering fetal-heart rate monitoring medical device. In this research work the harvester has a zig-zag uniform structure with a dual-hold composition and three proof masses that improves the harvester’s operational bandwidth. The goal of this study is to find the maximum power generated from the harvester with lowest frequency and large bandwidth for enhancing the effectiveness of the device. The Multi-step energy harvester has proved to be more effective in comparison to single-layer and multi-layer harvesters, respectively.

AbstractCa2KZn2(VO4)3:Sm3+ phosphors have been prepared via the conventional solid state reaction method. Under 331 nm excitation, undoped Ca2KZn2(VO4)3 phosphor exhibits broad emission in the range of 400 nm to 600 nm, centered at the 515 nm emission wavelength. Whereas, Sm3+ doped Ca2KZn2(VO4)3 phosphor exhibited three intense emission bands around 567, 601 and 648 nm due to 4G5/2− 6H5/2, 4G5/2− 6H7/2 and 4G5/2− 6H9/2 transition of Sm3+ ions, respectively. These results indicates that the synthesized Ca2KZn2(VO4)3:Sm3+ phosphors can be used as potential candidate for white light emitting diodes (WLEDs) and display devices.

AbstractThe prevailing use of sensing technologies has facilitated advanced research on the fabrication of sensors for various applications. As the demand for sensor technology continues to rise, there is also an increased need for fabrication methods that are inexpensive and fit for use. Most conventional fabrication methods are not adaptive to rapid design and material change. Strain gauge sensors play a vital role in monitoring subtle mechanical deformations in rigid bodies. Additive manufacturing techniques can be utilized to easily prototype sensors that fit the application’s specific geometric and material needs. Also, modifications of design in terms of both shape and substrate can be implemented and tested using rapid prototyping. Within this study, the performance of 3D-printed meandering-line strain gauge sensors is investigated. A design of experiments (DoE) was developed, wherein the parameters of line width, thickness, and shape were varied and their impact on performance is analyzed.

AbstractThe finite element numerical calculation can get the shock wave velocity and overpressure at any point in the explosion field, but some factors such as the parameter value of the state equation influence the calculation results. The tomography inversion can acquire the velocity and overpressure distribution of shock wave; however, the initial model and constraints can affect the inversion results. Aiming at the shortcoming of the two algorithms, this article combines the two methods and presents a new algorithm to reconstruct the explosion field. First, The LS-DYNA finite element program is applied to establish a numerical model and calculate the shock wave velocity and superpressure in air explosion. Second, generalized inversion with regularization tomography inversion algorithm is used to invert the shock wave field. In the inversion, the finite element calculation results are used as the initial model of inversion and constrain the inversion. The experiment results prove that the proposed algorithm can greatly improve the inversion accuracy and the iterative convergence speed. The inversion image can better depict the internal details of the explosion field and eliminate noise.

AbstractIn this article, by using the first-principles calculations based on density functional theory (DFT), we investigate the structural, electronic and optical properties of α-Li3BN2 under pressure up to 10 GPa. The obtained results indicate that the value of V/V0 basically decreases linearly with the increase of pressure. By increasing the pressure, α-Li3BN2 remains an indirect band gap semi-conductor. Although, the band gap of the α-Li3BN2 increases with pressure. Besides, the optical spectra exhibit anisotropy in the x and z directions and a small blue shift under pressure.

AbstractCobalt ferrite (CFO), barium titanate (BTO) core-shell nanoparticles (CFO:BTO NPs) exhibit multiferroic properties through the magnetoelectric effect. Inkjet printing is a direct-write, additive manufacturing technique for fabrication of electronic components and devices. Hansen Solubility Parameters (HSP) are a practical tool to understand solution and dispersion behavior of materials in a mixture. This work applies HSP analysis to improve CFO:BTO NPs synthesis and guide the ink formulation process. The estimated HSP values for CFO:BTO core-shell NPs (dD = 15.5, dP = 11.9, dH = 23, r = 4.6), CFO (dD = 15.9, dP = 10.6, dH = 22.5, r = 4.9), and BTO (dD = 16.6, dP = 9.7, dH = 15.4, r = 5.8) are analyzed. Limits and considerations of the HSP are discussed and results are combined with solvent thermal and fluid properties to develop ink formulations for multi-functional, multi-material inkjet printing applications.

AbstractxBaO–xTiO2–(100–2x)TeO2 (BTT) glass-ceramics were prepared through a melt-quenching synthesis method. Structural and optical properties, analyzed from Raman spectroscopy and absorption (OA) measurements, revealed that the increase in the TiO2 content promoted a loss in the network connectivity because of the formation of the non-bridging oxygen atoms (NBO’s) as well as the Te–O–Te bonds’ deformation. X-ray diffraction analysis confirmed the formation of ferroelectric nanocrystals (FeNCs) with tetragonal symmetry, related to the BaTiO3 phase, in the studied compositions, whose crystallinity seems to be intensified as the TiO2 concentration increases. The room temperature energy storage performance of these BTT samples, assessed using P-E hysteresis loops, confirmed excellent energy storage response and reveals the potential of the study glass-ceramics for practical applications.