The integrable substrate for THz modulation directly influences both the quality of films and THz absorption. Currently, the available THz substrate candidate library is still not clear. Here, we have carried out a systematic investigation of commonly used commercial substrates, including Si, quartz SiO2, MgO, Al2O3, GdScO3 and TbScO3 in the range of 0.4–1.6 THz. It is found that low resistance Si, TSO and GSO are certainly not appropriate for THz light modulation due to their relatively higher absorption and dielectric constant, while the rest show better THz transmittance, low refractive index and loss. However, the dielectric constant and refractive index of high resistance Si are generally two times larger than quartz SiO2, Al2O3 and MgO. Compared with Al2O3 and MgO, quartz SiO2 shows at least 50% lower dielectric constant, refractive index and absorption, making it the best candidate. Our research is believed to build the rich substrate candidate library for THz range light modulation.

Piezoelectric energy harvesting from mechanical vibrations has attracted considerable attention during the last decade. The homogeneous harvesters were studied experimentally or numerically by various models such as single degree of freedom (SDOF) modeling, finite element (FE) modeling as well as using analytical solutions. In this work, FE models for simulating a piezoelectric beam bimorph power harvester consisting of a laminated piezoelectric beam, a proof mass, and an electrical load (series or parallel connections) configurations are developed. The effects of the material and size of the substrate, the proof mass have been studied on the resonance frequencies and the output parameters of the piezoelectric generator (PEG). Numerical results obtained using the proposed procedure for piezoelectric bimorph power harvesters are in good agreement with the experimental data available in the literature. The proposed method can be used for modeling accurately this class of energy harvesting devices.

Antimony sulfoiodide (SbSI) is a highly efficient energy conversion piezoelectric material. We obtained SbSI doped with tin (II) ions according to the formula Sb1-xSnxSI1-x (x=0.01–0.1). This heterovalent doping has been performed by the novel method of synthesis in an aqueous solution. The introduction of tin cations leads to a material Curie point increase of more than 10 K. The samples containing 5 mol.% of the dopant possess the best piezoelectric properties: piezomodule d33～750 pC/N, dielectric constant at a frequency of 1 kHz — 1758, dielectric loss tangent — 0.054, and piezosensitivity — 50 mV × m/N. Thus, tin-doped SbSI is a promising material for highly efficient electromechanical transducers and sensors.

This study focuses on the properties of Vanadium and Copper co-doped Barium Zirconate Titanate (BZT) for potential technological applications. Various doping ratios of CuO:V2O5 were used to synthesize the materials, and X-ray diffraction (XRD) confirmed a tetragonal phase in all samples. The grain density and dimensions decreased with higher concentrations of V2O5 and CuO. FTIR spectra confirmed the compositional structure and bonding of the samples. The impedance analysis indicated that higher doping concentrations facilitated charge conduction at grain boundaries. Dielectric relaxation was studied using the Havriliak–Negami model and electrical modulus behavior was analyzed. Activation energy values from Arrhenius fitting matched those from impedance data, suggesting the same type of charge carriers. The study revealed that elevated levels of V concentration induced charge carriers to exhibit hopping behavior, thereby enhancing conductivity. Conversely, higher Cu concentration impeded hopping, leading to a swift rise in activation energy.

Graphene-oxide (GO) is one of the most commonly used carbon nanomaterials in advanced applications such as microwave absorption and EMI shielding, due to various advantages such as ease of synthesis and exfoliation, effective doping capability, and superior composite compatibility. In this study, we used the modified Hummer’s method to synthesize GO by exfoliating graphite powder, and a simple hydrothermal approach was employed for elemental doping and GO reduction. As nitrogen–sulfur (N, S) dual-doping precursors, thiourea and l-cysteine amino acids were utilized. The structural features and microporous network structure of GO aerogel foams were investigated. The microwave absorption capabilities of polyethersulfone-based nanocomposite films incorporating the as-produced nitrogen–sulfur enrich reduced GO (NS-rGO) are also explored. According to the physicochemical characterization, the existence of remarkable structural defects with a porous three-dimensional (3D) network was discovered due to heteroatom insertion and hydrothermal doping. Additionally, the dual-doped sample exhibited high Nitrogen and sulfur content of 8.93% and 13.19%, respectively. While NS-rGO possesses a higher conductivity of 174.7 μS compared to 12.65 μS for GO. The nanocomposites filled with NS-rGO foams demonstrated a high shielding efficiency (SE) of 45 dB in the X-band with a filler loading of 0.5 wt.%. This high SE arises from dopant heteroatoms and the heterogeneous interface, which induce interface polarization, thereby increasing microwave absorption and dielectric constant. It also results from multi-level reflections caused by the 3D porous structures. These findings offer valuable insights into the functionalization of carbon nanostructures and the development of 3D networks in GO-based functional materials, providing further guidance for engineering high-performance electromagnetic interference shielding materials.

In this paper, we studied the formation of self-organized domain arrays created by moving biased tip of scanning probe microscope (SPM) in deuterated TGS crystals. The shape of created domains depends significantly on scanning direction and applied voltage. For scanning along c axis, the domain shape drastically changed from arrays to stripe domains at 150 V. Scanning perpendicular to c axis led to formation of the array of the dashed domains. Increasing of the dashed domain length leads to change of domain shape from arrays of dashed domains to solid stripe domain. The obtained effect has been considered in terms of the kinetic approach as a result of formation of comb-like domain with charged domain walls in the bulk due to repetitive appearance of the domain spikes. The spontaneous backswitching under the action of the depolarization field leads to the fast growth of the tooth to the surface and results in the transformation of the domain shape. The computer simulation of the nonuniform motion of charged domain wall under the action of depolarization field has been done. The obtained results demonstrate the essential role of screening processes and pave the way for further improvement of domain engineering methods.

Piezoelectric materials are commonly used in transducers to convert electromechanical signals due to their energy conversion characteristics. We designed a PIMNT/epoxy 2–2 composite to take full advantage of the excellent beam-mode piezoelectric and acoustic features of PIMNT single crystals. Following the approach used for piezoelectric ceramic composites, we selected PIMNT piezoelectric single crystal and EPO-TEK301-2 epoxy resin for the composite, and combined finite element analysis with experimental preparation. We prepared, tested and analyzed 2–2 piezoelectric single crystal composites with varying volume fractions, which showed high electromechanical coupling properties (kt>75%) and low acoustic impedance (Z<20 MRayl). These encouraging findings suggest the possibility of devising high-performance ultrasonic transducers utilizing the PIMNT/epoxy 2–2 composite.

This paper presents the results of the first experimental observation of polarization reversal in the bulk of ferroelectric with a charged domain wall (CDW) under the action of an electric field on the example of a single crystal LiTaO3 plate. A CDW was obtained in the sample bulk at the locus of points with a sign change of the composition gradient which results from sample annealing in lithium rich atmosphere. Imaging of the domain structure in the bulk and its evolution on the surface made it possible to detect anomalous domain kinetics, which represents the growth of ledges on the CDW toward the polar surface. The main stages of the domain structure evolution on the polar surface, including the growth of isolated domains, as well as the formation and decay of the maze domain structure, were revealed. An analysis is made for the time dependence of the area fraction occupied by growing domains. We used a kinetic approach based on the analogy between the growth of domains and crystals to explain the obtained results.

Low-temperature co-fired ceramics (LTCC) applied in millimeter/microwave and terahertz frequencies (5G/6G) have attracted a lot of attention recently. In this study, MgO-based dielectric ceramics were successfully sintered at 950°C with the sintering aids: x wt.% of LiF fluoride (x=2, 4, 6, 8, 10) and 0.5 wt.% of BBSZ (Bi2O3–B2O3–SiO2–ZnO) glass. BBSZ glass was introduced as another sintering aid to facilitate the sintering and densification. Crystalline structure and micro-morphology were investigated and analyzed. Dielectric properties (εr, Q×f, τf) at millimeter/microwave and terahertz wave frequencies were also studied. The ionic characteristics of Mg–O bond (fi), the lattice energy (U) and the bond energy (E) were calculated and analyzed. It is suggested that the optimal x=4, where εr=10.5, Q×f=120,000 GHz (@12 GHz) and τf=?26 ppm/°C at millimeter/microwave range. When the frequency was up to terahertz (1.0 THz), the εr values were 8.8–9.35 and the tanδ were 5.6×10?3–8.7×10?3. The experimental results indicated that the low-temperature sintered MgO-based ceramics have potential for millimeter/microwave and terahertz communication applications.