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Highly effective electromagnetic (EM) wave absorber materials with strong reflection loss (RL) and a wide absorption bandwidth (EBW) in gigahertz (GHz) frequencies are crucial for advanced wireless applications and portable electronics. Traditional microwave absorbers lack magnetic loss and struggle with impedance matching, while ferrites are stable, exhibit excellent magnetic and dielectric losses, and offer better impedance matching. However, achieving the desired EBW in ferrites remains a challenge, necessitating further composition design. In this study, impedance matching is successfully enhanced and EBW in Ni–Zn ferrite is broadened by successive doping with Mn and Co , without incorporation of any polymer filler. It is found that Ni0.4Co0.1Zn0.5Fe1.9Mn0.1O4 material exhibits exceptional EM wave absorption, with a maximum RL of −48.7 dB. It also featured a significant EBW of 10.8 GHz, maintaining a 90% absorption rate (RL < −10 dB) for a thickness of 4.5 mm. These outstanding properties result from substantial magnetic losses and favorable impedance matching. These findings represent a significant step forward in the development of microwave absorber materials, addressing EM wave pollution concerns within GHz frequencies, including the frequency band used in popular 5G technology. [ABSTRACT FROM AUTHOR]

To fulfill the demands of more bandwidth in 5G and 6G communication technology, new dielectric substrates that can be co‐fired into packages and devices that have low dielectric loss and improved thermal conductivity are desired. The motivation for this study is to design composites with low dielectric loss (tan δ) and high thermal conductivity (κ), while still limiting the electrical conductivity, for microwave applications involving high power and high frequency. This work describes the fabrication of high‐density electroceramic composites with a model dielectric material for cold sintering, namely sodium molybdate (Na2Mo2O7), and fillers with higher thermal conductivity such as hexagonal boron nitride. The physical properties of the composites were characterized as a function of filler vol.%, temperature, and frequency. Understanding the variation in measured properties is achieved through analyzing the respective transport mechanisms. [ABSTRACT FROM AUTHOR]

2D/3D bilayer perovskite synthesized using sequential deposition methods has shown effectiveness in enhancing the stability of perovskite solar devices. However, these approaches present several limitations such as uncontrolled chemical processes, disordered interfacial states, and microscale heterogeneities that can chemically, structurally, and electronically compromise the performance of solar modules. Here, this work demonstrates an emulsion‐based self‐assembly approach using natural lipid biomolecules in a nonionic solution system to form a 0D/3D bilayer structure. The new capping layer is composed of 0D‐entity nanoparticles of perovskite encapsulated by a hydrophobic lipid membrane, analogous to a cell structure, formed through a molecular self‐assembly process. This 0D layer provides a strong water repellent characteristics, optimum interface microstructure, and excellent homogeneity that drives significant enhancement in stability. Solar modules with a large active area of 70 cm2 fabricated using films comprising of 0D/3D bilayer structure are found to show consistent efficiency of >19% for 2800 h of continuous illumination in the air (60% relative humidity). This emulsion‐based self‐assembly approach is expected to have a transformative impact on the design and development of stable perovskite‐based devices. [ABSTRACT FROM AUTHOR]

Ultrasound medical imaging is an entrenched and powerful tool for medical diagnosis. Image quality in ultrasound is mainly dependent on performance of piezoelectric transducer elements, which is further related to the electromechanical performance of the constituent piezoelectric materials. With rising need for piezoelectric materials with better performance and low cost, a highly $\langle 001\rangle $ textured piezo ceramic, Pb(Mg1/3Nb2/3)O3-Pb(Zr, Ti)O3, has been developed. Recently, textured ceramic materials can be produced at low cost and exhibit high piezoelectric strain constants and large electromechanical coupling coefficients. In this work, 15-MHz ultrasonic transducers with an effective aperture of 2.5 mm in diameter based on these highly $\langle 001\rangle $ textured ceramics have been successfully fabricated. The fabricated transducers achieved a central frequency of 15 MHz, a fractional bandwidth of 67% (at −6 dB), a high effective electromechanical coupling coefficient ${k}_{\text {eff}}$ of 0.55, and a low insertion loss (IL) of 21 dB. Ex vivo ultrasonic imaging of a porcine eyeball was used to assess the tomography quality of the transducer. The results show that utilized textured ceramic has a great potential in developing ultrasonic devices for biomedical imaging purposes. [ABSTRACT FROM AUTHOR]

Mechanically resilient optoelectronic devices are relevant for a wide range of applications, including portable and wearable devices. Perovskite thin film‐based devices are a suitable choice for designing such resilient systems as it demonstrates high performance while preserving moderate mechanical compliance. Yet its mechanical property can be improved further by integrating the energy dissipation system and self‐healing ability into the thin film. Copolymers containing Lewis‐base functional groups, elastomer chains, and cyclic linkages are synthesized and introduced into the perovskite precursor. The polymers impart multifunctional effect of controlled crystal growth, defect passivation, protection against moisture, mechanical energy dissipation, and self‐recoverability. The polymer‐added perovskite solar cells are shown to provide a power conversion efficiency of 23.25% (a steady‐state efficiency of 22.61%), due to the strong coordinative covalent interaction between the polymer and the perovskite. An operational lifetime of solar cells under harsh conditions is also substantially extended by the polymer incorporation. Furthermore, the interchain hydrogen‐bond strength controlled by the cyclic linkage, and hybrid cross‐linked network formed within the thin film significantly improves the mechanical stability and self‐recoverability of the thin film. As a result, the devices demonstrate robustness under 2000 cyclic flex tests at a bending radius of 1 mm. [ABSTRACT FROM AUTHOR]

Quantifying digestive and fermentative processes within the rumen environment has been the subject of decades of research; however, our existing research methodologies preclude time-sensitive and spatially explicit investigation of this system. To better understand the temporal and spatial dynamics of the rumen environment, real-time and in situ monitoring of various chemical and physical parameters in the rumen through implantable microsensor technologies is a practical solution. Moreover, such sensors could contribute to the next generation of precision livestock farming, provided sufficient wireless data networking and computing systems are incorporated. In this review, various microsensor technologies applicable to real-time metabolic monitoring for ruminants are introduced, including the detection of parameters for rumen metabolism, such as pH, temperature, histamine concentrations, and volatile fatty acid concentrations. The working mechanisms and requirements of the sensors are summarized with respect to the selected target parameters. Lastly, future challenges and perspectives of this research field are discussed. [ABSTRACT FROM AUTHOR]

Refractory multicomponent alloys (RMCAs) have garnered attention as potential materials for high-temperature structural applications, due to their excellent mechanical properties. However, conventional alloy design has limitations in terms of constrained compositional space and a lack of computational databases with adequate coverage. To address this, we present a design framework that leverages machine learning (ML), the CALculation of PHAse Diagram (CALPHAD) method, and experimental validation to efficiently develop refractory alloys. The present study focuses on the Mo-Nb-W ternary system. Six ternary alloys were inversely designed by means of the conditional generative adversarial network (cGAN) and fabricated via arc melting. The ternary alloys exhibit a single BCC phase which is consistent with CALPHAD calculations as well as Scheil simulations. The present interactive design loop between the ML surrogate model and experiments is demonstrated through the accurate hardness prediction, resulting in cGAN models capable of rapid exploration of the higher-order design space. The hardness of the Mo-Nb-W alloys is in the range of 5–6 GPa due to their solid solution strengthening. [Display omitted] • Inverse design integrating machine learning, CALPHAD and experimental validation of Mo-Nb-W alloys has been developed. • The microstructure of six Mo-Nb-W ternary compounds has been analyzed, which agrees with CALPHAD simulations. • The Vickers hardness has been accurately predictedthrough the iteration of the model. • The solid solution strengthening mechanism of high hardness has been clarified. [ABSTRACT FROM AUTHOR]

Piezoelectric materials enable the conversion of mechanical energy into electrical energy and vice-versa. Ultrahigh piezoelectricity has been only observed in single crystals. Realization of piezoelectric ceramics with longitudinal piezoelectric constant (d33) close to 2000 pC N-1, which combines single crystal-like high properties and ceramic-like cost effectiveness, large-scale manufacturing, and machinability will be a milestone in advancement of piezoelectric ceramic materials. Here, guided by phenomenological models and phase-field simulations that provide conditions for flattening the energy landscape of polarization, a synergistic design strategy is demonstrated that exploits compositionally driven local structural heterogeneity and microstructural grain orientation/texturing to provide record piezoelectricity in ceramics. This strategy is demonstrated on [001]PC-textured and Eu3+-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) ceramics that exhibit the highest piezoelectric coefficient (small-signal d33 of up to 1950 pC N-1 and large-signal d33* of ≈2100 pm V-1) among all the reported piezoelectric ceramics. Extensive characterization conducted using high-resolution microscopy and diffraction techniques in conjunction with the computational models reveals the underlying mechanisms governing the piezoelectric performance. Further, the impact of losses on the electromechanical coupling is identified, which plays major role in suppressing the percentage of piezoelectricity enhancement, and the fundamental understanding of loss in this study sheds light on further enhancement of piezoelectricity. These results on cost-effective and record performance piezoelectric ceramics will launch a new generation of piezoelectric applications. [ABSTRACT FROM AUTHOR]

Future advancements in three-dimensional (3D) electronics require robust thermal management methodology. Thermoelectric coolers (TECs) are reliable and solid-state heat pumping devices with high cooling capacity that can meet the requirements of emerging 3D microelectronic devices. Here, we first provide the design of TECs for electronics cooling using a computational model and then experimentally validate the main predictions. Key device parameters such as device thickness, leg density, and contact resistance were studied to understand their influence on the performance of TECs. Our results show that it is possible to achieve high cooling power density through optimization of TE leg height and packing density. Scaling of TECs is shown to provide ultra-high cooling power density. [ABSTRACT FROM AUTHOR]

Traditional organic–inorganic halide perovskites (OIHPs), in which perovskites layers are separated by an organic spacer material, have been mainly explored for photovoltaics devices, but they also offer promises for nonlinear optics and quantum light applications. These attributes include (a) high quantum efficiency, (b) large binding energy of excitons in low-dimensional structures, (c) polarons of long coherence times at room temperature, and (d) a large spin–orbit coupling. OIHP systems can be engineered to have photoluminescence (PL) emissions from UV to IR regions, in addition to power conversion efficiencies, in excess of 24%. This class of materials offers broad tunability of its properties, through controlling the number of atomic layers in the quantum well, tuning the organic spacer thickness, or even engineering the composition with exotic dopants. In this work, we present PL and time-resolved PL measurements of quasi-2D BA2PbI4 and provide new insights on the temperature dependence of their excitonic dynamics and fine structures of their PL emissions. We observed long lifetimes, which can result from the formation of large polarons, screening the Coulomb interactions of the charge carriers and reducing the scattering of the carriers with charge defects. [ABSTRACT FROM AUTHOR]

Smart electronic devices are becoming ubiquitous due to many appealing attributes including portability, long operational time, rechargeability and compatibility with the user-desired form factor. Integration of mobile power sources (MPS) based on photovoltaic technologies with smart electronics will continue to drive improved sustainability and independence. With high efficiency, low cost, flexibility and lightweight features, halide perovskite photovoltaics have become promising candidates for MPS. Realization of these photovoltaic MPS (PV-MPS) with unconventionally extraordinary attributes requires new 'out-of-box' designs. Natural materials have provided promising designing solutions to engineer properties under a broad range of boundary conditions, ranging from molecules, proteins, cells, tissues, apparatus to systems in animals, plants, and humans optimized through billions of years of evolution. Applying bio-inspired strategies in PV-MPS could be biomolecular modification on crystallization at the atomic/meso-scale, bio-structural duplication at the device/system level and bio-mimicking at the functional level to render efficient charge delivery, energy transport/utilization, as well as stronger resistance against environmental stimuli (e.g., self-healing and self-cleaning). In this review, we discuss the bio-inspired/-mimetic structures, experimental models, and working principles, with the goal of revealing physics and bio-microstructures relevant for PV-MPS. Here the emphasis is on identifying the strategies and material designs towards improvement of the performance of emerging halide perovskite PVs and strategizing their bridge to future MPS. [ABSTRACT FROM AUTHOR]

The determination of complex elastic, piezoelectric, and dielectric coefficients of piezoelectric ceramics is important for precision engineering devices. Here, a novel method for determining the optimal material coefficients is presented. This method minimizes the average relative error in the values of conductance, susceptance, resistance, and reactance obtained from the 1-D model in the IEEE Standard (ANSI/IEEE Std 176-1987) and the experimental measurements of the first and second radial modes. Poisson’s ratio is assumed to be a complex number in addition to the elastic, piezoelectric, and dielectric coefficients in the present method. The global minimum of the average relative error is found by searching the minimum among all local minima of the average relative error, which are obtained with the Levenberg–Marquardt modification of Newton’s method from randomly chosen initial conditions. The optimal material coefficients of an APC 850 disk and an APC 855 disk are calculated with this method. The uncertainties in the optimal material coefficients are evaluated by calculating the minimum average relative error when the real or imaginary part of each coefficient is prescribed. [ABSTRACT FROM AUTHOR]

Single crystals of 71PMN-6PZ-23PT [71Pb(Mg1/3Nb2/3)O3-6PbZrO3-23PbTiO3] oriented along the thickness direction (011) with and without Mn doping were grown by a solid-state single-crystal growth method, and pyroelectric properties of the crystals were investigated. Though the pyroelectric coefficient of a Mn doped crystal is not significantly higher than the un-doped one at room temperature (RT), a large enhancement was observed after 0.7 mol. % Mn doping at high temperatures (>100 °C). Furthermore, the FoMs for practical applications at RT, the Mn doped crystal showed large enhancement as compared to the un-doped one. The presented single crystals also yielded excellent figure of merit (FoM) values for pyroelectricity: Fi, Fv, and FD were 3.5 × 10−10 m V−1, 0.02 m2 C−1, and 2.68 × 10−5 Pa−1/2, respectively, at RT. The large pyroelectric response in the Mn-doped single crystal is attributed to the large ferroelectric polarization and low dielectric constant and dielectric loss. The demonstrated pyroelectric response in the Mn-doped 71PMN-6PZ-23PT single crystal shows that it exhibits excellent potential for various thermal sensor applications. [ABSTRACT FROM AUTHOR]

Even though ZnO is commonly used as the ETL in the perovskite solar cell (PSC), the reactivity of perovskite deposited thereupon limits its performance. Herein, an ethylene diamine tetraacetic acid‐complexed ZnO (E‐ZnO) is successfully developed as a significantly improved electron selective layer (ESLs) in perovskite device. It is found that E‐ZnO exhibits higher electron mobility and better matched energy level with perovskite compared to ZnO. In addition, in order to eliminate the proton transfer reaction at the ZnO/perovskite interface, a high quality perovskite film fabrication process that requires neither annealing nor antisolvent is developed. By taking advantages of both E‐ZnO and the new process, the highest efficiency of 20.39% is obtained for PSCs based on E‐ZnO. Moreover, the efficiency of unencapsulated PSCs with E‐ZnO retains 95% of its initial value exposed in an ambient atmosphere after 3604 h. This work provides a feasible path toward high performance of PSCs, and it is believed that the present work will facilitate transition of perovskite photovoltaics in flexible and tandem devices since the annealing‐ and antisolvent‐free technology. [ABSTRACT FROM AUTHOR]

Even though ZnO is commonly used as the ETL in the perovskite solar cell (PSC), the reactivity of perovskite deposited thereupon limits its performance. Herein, an ethylene diamine tetraacetic acid‐complexed ZnO (E‐ZnO) is successfully developed as a significantly improved electron selective layer (ESLs) in perovskite device. It is found that E‐ZnO exhibits higher electron mobility and better matched energy level with perovskite compared to ZnO. In addition, in order to eliminate the proton transfer reaction at the ZnO/perovskite interface, a high quality perovskite film fabrication process that requires neither annealing nor antisolvent is developed. By taking advantages of both E‐ZnO and the new process, the highest efficiency of 20.39% is obtained for PSCs based on E‐ZnO. Moreover, the efficiency of unencapsulated PSCs with E‐ZnO retains 95% of its initial value exposed in an ambient atmosphere after 3604 h. This work provides a feasible path toward high performance of PSCs, and it is believed that the present work will facilitate transition of perovskite photovoltaics in flexible and tandem devices since the annealing‐ and antisolvent‐free technology. [ABSTRACT FROM AUTHOR]

The physical properties (dielectric, ferroelectric, piezoelectric, etc.) of complex perovskite ferroelectrics depend on the degree of order/disorder and the scale of the ordered domains. In this study, the electrocaloric (EC) properties of three representative complex perovskite ferroelectrics, Pb(Mg 1/3 Nb 2/3)O 3 –8PbTiO 3 (PMN-8PT), 1mol% Sm-doped Pb(Mg 1/3 Nb 2/3)O 3 –8PbTiO 3 (1S-PMN-8PT) and Pb(Sc 1/2 Ta 1/2)O 3 (PST) are evaluated. Multi-layer ceramic capacitors (MLCCs) with identical structural configurations were fabricated for these three compounds, and their EC properties were characterized by direct measurement using a thermocouple. The EC temperature change Δ T of PMN-8PT, 1S-PMN-8PT and PST MLCCs under 20 V μm−1 at room temperature were found to be 1.42 K, 1.54 K, and 3.10 K, respectively. X-ray diffraction and high-resolution transmission electron microscopy data suggests that the high EC performance of PST is related to the ordering of B-site cations (Sc3+ and Ta5+) with the ordering parameter S = 0.82 and a long coherence length of ∼100 nm, such that the sample transitioned from a relaxor ferroelectric to a normal ferroelectric. These results provide pathway towards design of high performance EC materials required for solid state refrigeration and air-conditioning technologies. Multi-layer ceramic capacitors for three representative complex perovskite ferroelectrics, Pb(Mg 1/3 Nb 2/3)O 3 –8PbTiO 3 (PMN-8PT), 1mol% Sm-doped Pb(Mg 1/3 Nb 2/3)O 3 –8PbTiO 3 (1S-PMN-8PT) and Pb(Sc 1/2 Ta 1/2)O 3 (PST), were fabricated. Their EC temperature change Δ T under 20 V μm−1 at room temperature were 1.42 K, 1.54 K, and 3.10 K, respectively. The high EC performance of PST is related to the long-range ordering of B-site cations (Sc3+ and Ta5+). [Display omitted] [ABSTRACT FROM AUTHOR]

Piezoelectric ceramics with combinatory soft and hard characteristics are highly desired for high-power applications. However, it remains grand challenge to achieve simultaneous presence of hard (e.g. high coercive field, E c ; high mechanical quality factor, Q m) and soft (e.g. high piezoelectric constant, d ; high electromechanical coupling factor, k) piezoelectric properties in piezoelectric ceramics since the mechanism controlling the hard behavior (pinned domain walls) will significantly reduce the soft behavior. Here, we address this grand challenge and demonstrate <001> textured MnO 2 and CuO co-doped Pb(In 1/2 Nb 1/2)O 3 - Pb(Mg 1/3 Nb 2/3)O 3 -PbTiO 3 (PIN-PMN-PT) ceramics exhibiting ultrahigh combined soft and hard piezoelectric properties (d 33 = 713 pC N−1, k 31 = 0.52, Q m ≈950, E c = 9.6 kV cm−1, tan δ = 0.45%). The outstanding electromechanical properties are explained by considering composition/phase selection, crystallographic anisotropy and defect engineering. Phase-field model in conjunction with high resolution electron microscopy and diffraction techniques is utilized to delineate the contributions arising from intrinsic piezoelectric response, domain dynamics, and local structural heterogeneity. These results will have significant impact in the development of high-power transducers and actuators. [Display omitted] [ABSTRACT FROM AUTHOR]

• Decoupled backpack generates energy from the pack-mass suspended only on springs. • Power and efficiency derivation for semi-coupled, decoupled and coupled backpacks. • Coupled and semi-coupled harvester response is verified using Simulink models. • Experimental coupled backpack harvesters indicated high normalized force. • Efficiency of semi-coupled and decoupled backpacks is higher than coupled backpack. Harvesting energy from human motion has the potential to power wearable sensors and low power portable systems. Here, a backpack harvester that generates electrical energy by suspending the pack-mass only on springs is demonstrated. In this mechanism, the relative motion between a fixed frame (relative to the body) and a suspended frame winds a torsional spring that serves as a mechanical reservoir in one-half of the oscillation cycle (one walking step). In the second half cycle, the stored energy is released to the generator. This approach eliminates the damping force from the generator on the human bearing the load. As the load is suspended on springs and does not directly drive the generator, the proposed system results in a decoupled harvester. Experimental results demonstrate that the output power generated from the decoupled harvester is 65% of that obtained from a semi-coupled harvester with 52% smaller backpack displacements and oscillatory forces. The decoupled and semi-coupled backpack harvesters achieved 53% and 45% efficiency at 1.4 m/s walking speed compared to 34% efficiency in a fully coupled harvester. This demonstrates significant advancement towards developing decoupled backpack energy harvesters that suspend pack-mass only on springs. [ABSTRACT FROM AUTHOR]

• Large, thin, and light-weight thermoacoustic projectors benefit from encapsulation • Plate-cavity coupling modifies vibration modes of the plate • Modified vibration profile is favorable for plane-wave radiation of the sound • Proper choice of cavity and plate geometry provides a desirable performance • Increase of acoustic stiffness of the entrained gas increases the bandwidth of device • Coupling of internal pressure with modified modes provides a high performance The problem of coupled panel-cavity vibrations is addressed by studying the resonance modes in high power, low frequency, encapsulated thermoacoustic sound projectors using scanning laser vibrometry and sound pressure measurements. We fabricated and analyzed the performance of large area thermoacoustic sound projectors based on freestanding carbon nanotube sheets, encapsulated between a heat sink and various rigid vibrating plates. For thin, simply-supported vibrating plates we observed a strong deviation of resonance frequency and sound intensity from theoretical prediction for in vacuo plates. The domination of symmetric, odd modes for thin plates, with substantially improved sound radiation, is attributed to the coupled panel-cavity modes produced by harmonically varying pressure within the cavity. The observed modified mode shapes result from a minimum energy principle, wherein the potential energy stored in the entrained gas is minimized by reducing the overall change of the cavity gas volume. The effect of plate and cavity thickness on thermoacoustic projector performance in air is described for various devices. The optimized ultralight, low volume sound projectors can generate a remarkably high sound pressure level in air of over 120 dB re 20 μPa @ 1 m in a frequency range of 500 - 3000 Hz. [Display omitted] [ABSTRACT FROM AUTHOR]