Piezoelectric materials used in transducer applications suffer from thermal depolarization, resulting in performance degradation or complete loss of their piezoelectricity. Self-poling is a promising phenomenon, as it enables ferroelectric materials to spontaneously develop net polarization and exhibit piezoelectric response without a conventional poling process. However, the mechanism of self-poling in bulk ferroelectric materials remains controversial and unclear. Here, we demonstrate that inhomogeneous physical properties in the bulk ferroelectric single crystals can induce flexoelectricity-driven unidirectional self-poling. We confirmed the presence of inhomogeneous lattice parameters, thermal expansion coefficients, and phase transition temperatures along the [001] direction in the Mn-doped 0.71Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 single crystal through in-situ high-energy synchrotron radiation X-ray diffraction analysis. These inhomogeneities allow the single crystal to preserve its non-centrosymmetric state along the [001] direction well above TC and enable thermal activation of the self-poling even below TC. These self-poling ferroelectrics are expected to resolve critical reliability issues in future electronic applications.

Ferroelectric materials exhibit strong electromechanical coupling, largely influenced by their domain structures. Numerous microstructural studies indicate that smaller domains with higher domain wall density generally enhance domain wall motion, although some inconsistencies have been reported. In this work, we use X-ray photon correlation spectroscopy (XPCS) to probe dynamic response in Pb(Mg1/3Nb2/3)O3-29PbTiO3 (PMN-29PT) single crystals under applied electric fields. We introduce a two-field correlation approach, adapted from conventional two-time correlation to quantify dynamics. Statistical analysis reveals that both [001]-oriented direct current (DC) and alternating current (AC) poled samples show Poisson-like behavior within specific electric field regions. The DC-poled samples exhibit more frequent domain wall jump events but with smaller amount of decorrelation per jump event, whereas the AC-poled samples show fewer jump events with larger decorrelation per jump event. This observation aligns with the prevalence of 109 degrees domain walls in the AC-poled samples, which contribute to more domain wall motion. These findings provide experimental evidence of collective domain wall motion and establish a direct connection between mesoscale dynamics and electromechanical response.

To address thermo-mechanical challenges in power module substrates, this study investigates three Insulated Metal Substrate (IMS) designs with varied copper layer thicknesses. Finite element analysis (FEA) was employed to predict thermal resistance and mechanical warpage, followed by experimental validation through warpage measurements and dielectric insulation tests. The objective is to identify an optimal IMS configuration that balances thermal performance with mechanical reliability, thereby providing a robust substrate solution for next-generation power electronics.

Silicon Carbide (SiC) power modules offer superior switching performance in medium and high voltage (MV and HV) applications but are prone to partial discharge (PD) due to high electric field concentrations. This paper focuses on techniques to mitigate electric field intensity, including stacked substrates, segregated copper pads, filled cavities, and protruded dielectrics, to enhance the PD performance of SiC power modules. A simulation-based co-design framework is introduced to incorporate both electric field and thermomechanical effects. Additionally, a non-dominated sorting genetic algorithm (NSGA) is employed to explore the trade-offs between PD mitigation and the die-attach solder fatigue life under power cycling. The optimization results indicate a 67.5% reduction in electric field intensity compared to conventional 10 kV designs, highlighting the effectiveness of the method in improving PD performance. Furthermore, a comparison of different substrate materials reveals that increasing the number of stacked layers significantly impacts the thermomechanical reliability of modules using epoxy resin composite dielectric (ERCD) and Al2O3 substrates, whereas AlN-based modules are less affected.

Relaxor-based ferroelectric single crystals possess colossal piezoelectric and dielectric properties and have been attractive for a wide range of electromechanical applications including transducers, sensors, and actuators. However, domain dynamics of relaxor ferroelectric single crystals are still not fully understood despite significant progress in the last three decades, partly because of the combined relaxor and normal ferroelectrics with complex domain structures within the material. Without a comprehensive understanding of domain dynamics, rational domain engineering for high piezoelectricity is challenging. In this review, we review experimental methods for characterizing domain dynamics in nanoscale and bulk mesoscale that exhibit both intrinsic and extrinsic contributions. We focus on literature published since 2010 and critically evaluate their strengths and limitations. From an overview of recent understanding, we highlight the need for real-time observations at appropriate time and length scales and cross-validation of different methods for precise measurements of domain dynamics.

Alternating current (AC) poling has been found to be more effective in optimizing the performance of [001]-oriented rhombohedral relaxor-PbTiO3 single crystals. However, these materials undergo ferroelectric phase transformations, during which structural changes result in loss of polarization and property degradation. In this study, we focus on a strategy to mitigate phase transformation-induced depolarization in Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) single crystals through high-temperature AC poling. Our results reveal that thermal depolarization is significantly reduced when AC poling is conducted at high temperature near the rhombohedral-to-tetragonal transformation temperature compared to the room-temperature poling. Furthermore, in-situ X-ray diffraction and Raman spectroscopy demonstrates that high-temperature AC poling can achieve a metastable phase and suppress symmetry changes during the ferroelectric phase transformation, contributing to reduced property degradation in the materials. Our findings highlight the potential of a novel domain engineering technique to enhance structural stability and mitigate depolarization in PMN-PT single crystals.

Copper-filled via is a critical component of advanced electronic packaging technologies. Embedded in interposer substrate, vias provide enhanced electrical performance in 2.5-D and 3-D electronic packaging by allowing a smaller form factor. In addition to the electrical characteristics of an electronic package, its thermal and mechanical performance also depends on via geometry and the interposer material. This necessitates a co-design approach integrating thermal, mechanical, and electrical considerations. This article focuses on a numerical parametric study and multiobjective machine learning-based optimization of through-silicon via (TSV) and through-glass via (TGV). This study investigates the multidisciplinary effects of aspect ratio (AR) and pitch in the square and hexagonal array vias. Copper protrusion, thermal resistance, and electrical parasitics were used as the optimization performance indicators. An online artificial neural network (ANN) algorithm, as well as the conventional genetic algorithm (GA), was adopted to optimize the through-via designs. The parametric study demonstrated that glass substrates are more effective in reducing copper protrusion and mutual capacitance up to 47.5% and 67.6% compared to silicon. However, TSVs showed superior thermal performance. A higher AR helps minimize the copper protrusion for mechanical performance. Moreover, the thermal performance was enhanced by reducing the pitch and using hexagonal array vias. Regarding electrical performance, a high pitch and low AR are preferable to minimize electrical parasitics. Finally, a 61.3% decrease in the computation time was achieved by using an online ANN-based optimization scheme compared to GA, highlighting its potential in the optimization of high-fidelity complex electronic designs.

The understanding of domain dynamics in ferroelectric materials is crucial for optimizing their performance in piezoelectric and electro-optic applications. Although previous studies have focused on static domain structures and macroscopic characteristics, the time-resolved approach of domains remains largely unexplored. In this study, we compare the dynamic responses of direct current (DC) and alternating current (AC) poled [001]-oriented rhombohedral Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) single crystals using X-ray photon correlation spectroscopy (XPCS) during the application of external electric fields. Our results demonstrate that the AC-poled sample exhibit enhanced reconfiguration of domain variants in response to driving fields compared to the DC-poled counterpart, as evidenced by accelerated correlation decay and faster relaxation time. This phenomenon is attributed to enhanced reversible domain wall motion achieved through AC poling, which facilitates field-induced domain realignment. These findings provide insight into the relationship between dynamics and macroscopic properties in relaxor-PT single crystals for high-performance applications.

Relaxor-PbTiO3 single crystals are distinguished by remarkable electromechanical properties, making them valuable for applications in ultrasound transducers. Although many studies have explained the high performance of these materials, real-time observation of dynamics remains challenging. In this study, we investigate correlation dynamics in Pb(Mg1/3Nb2/3)O-3-PbTiO3 (PMN-PT) rhombohedral single crystals using X-ray photon correlation spectroscopy (XPCS). Two crystal orientations, [111] and [001], are examined under bipolar electric field to understand their polarization switching behavior. The correlation decay patterns are analyzed using the Kohlrausch-Williams-Watts (KWW) model, providing quantitative insights into the rate of nucleation and growth. XPCS measurements reveal significantly shorter relaxation times in the [001]-poled sample compared to the [111]-poled counterpart. This enhanced dynamics in the [001]-poled specimen correlates with superior permittivity and piezoelectric coefficient (d(33)), which indicates enhanced domain wall motion as interpreted through classical nucleation and growth mechanisms.

Understanding the depolarization of ferroelectric materials caused by external stimuli is critical for maintaining the aligned polarization states. Although thermal depolarization in poled materials is well established, the mechanisms of electric field-induced depolarization remain largely unexplored. In this study, we investigate the electrical depoling behavior of [001]-oriented rhombohedral Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) single crystals poled using direct current poling (DCP) and alternating current poling (ACP). We reveal that the ACP sample exhibits a lower reverse coercive field than the DCP specimen. We compare the effects of bipolar and unipolar electric fields applied in the reverse poling direction, analyzing the changes in permittivity and piezoelectric resonance. Piezoresponse force microscopy is employed to characterize domain configurations in poled and electrically depoled samples. Our findings suggest that property degradation may arise from the nucleation and growth of domains oriented opposite to the initial arrangement.

The understanding of domain dynamics in ferroelectric materials is crucial for optimizing their performance in piezoelectric and electro‐optic applications. Although previous studies have focused on static domain structures and macroscopic characteristics, the time‐resolved approach of domains remains largely unexplored. In this study, we compare the dynamic responses of direct current (DC) and alternating current (AC) poled [001]‐oriented rhombohedral Pb(Mg 1/3 Nb 2/3 )O 3 –PbTiO 3 (PMN–PT) single crystals using X‐ray photon correlation spectroscopy (XPCS) during the application of external electric fields. Our results demonstrate that the AC‐poled sample exhibit enhanced reconfiguration of domain variants in response to driving fields compared to the DC‐poled counterpart, as evidenced by accelerated correlation decay and faster relaxation time. This phenomenon is attributed to enhanced reversible domain wall motion achieved through AC poling, which facilitates field‐induced domain realignment. These findings provide insight into the relationship between dynamics and macroscopic properties in relaxor‐PT single crystals for high‐performance applications.

This paper reviews the recent development of piezoelectric materials, structures, devices, and their applications in cryogenic environments (< 120 K). It is known that cryogenic environment presents challenges for piezoelectric materials since most of them lose majority of their piezoelectricity at low temperatures. Recently, it was found that some types of these materials, such as relaxor-PT single crystals, can still maintain reasonably high piezoelectric properties in cryogenic environments. In this review paper, the effect of cryogenic temperature on the piezoelectric materials is surveyed, and the methods to tailor the piezoelectric materials for proper functions at cryogenic temperatures (such as doping, changing the material composition, and engineering defects) are discussed and compared. The recent progress on piezoelectric structures for cryogenic space exploration as well as quantum and biomedical applications are then reviewed and discussed. Lastly, the challenges and future perspectives of piezoelectric materials and their associated applications are introduced.

Re-poling of unexpected partially depoled piezoelectric materials conventionally needs to be first fully depoled through annealing above their Curie temperature to revive piezoelectric performances. Here, we investigated de-poling and re-poling of Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals under electric fields at room temperature. We found that alternating current electric fields with amplitudes near the coercive field at low frequencies (<10 Hz) can be employed to successfully depolarize poled crystals at room temperature. We also demonstrated a reversible polarization switching process with a relaxor-PbTiO3 single crystal ultrasound transducer without device performance degradations. This experimental observation is supported by phase-field simulation, showing that alternating current electric fields can readily induce de-poling at room temperature, while direct current electric fields induce a transient depoled state only within an uncontrollable short period of time. The findings suggest new strategies for unprecedented in-device tailoring of the polarization states of ferroelectric materials. The authors find that alternating current electric fields with amplitudes near the coercive field at low frequencies (<10 Hz) can be employed to depolarize poled relaxor-PbTiO3 single crystals at room temperature, without conventional heat treatment.

Lithium Iron Phosphate (LiFePO4) microstructures have been synthesized using the sol-gel process. One-dimensional (1D) LiFePO4 microstructures were fabricated using tissue paper as a template under different temperatures to form pure phase microstructures. XRD analysis confirmed the single phase nature of orthorhombic olivine-structured LiFePO4 with Pnma space group. SEM analysis authenticated the formation of 1D LiFePO4 microstructures along with some clusters of particles. LiFePO4-multi-walled carbon nanotubes (MWCNT) freestanding sheets were prepared using a tape-casting process. Further, the electrochemical properties of LiFePO4-MWCNT freestanding sheet were analyzed through electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic charge-discharge analysis.

Scalable manufacturing of micro- and nanoscale textured surfaces from polymer composites is desirable in many applications from drag reduction in ship applications to energy-efficient radiative cooling of infrastructure. Creation of such surfaces, however, remains a challenge. By exploiting the ribbing phenomena that arise when viscous forces dominate over surface tension forces, we can create topographic patterns using roll-to-roll manufacturing techniques. In this work, we analyze how the rheology of yield stress fluids impacts the morphology of roll-coated surfaces using polydimethylsiloxane (PDMS) samples enhanced to varying degrees with multiwalled carbon nanotubes (CNTs) and fumed silica. We observe that CNTs increasingly dominate the large amplitude oscillatory shear response of PDMS composites. However, their impact is modified by the presence of fumed silica, which introduces a transition from intracycle strain softening to hardening behavior. The roll coating behavior of these PDMS composites is examined using image processing to link the rheological properties with the resulting surface morphologies, specifically focusing on two parameters defining surface morphology-ribbing wavenumber and branching patterns. While both types of PDMS composites display comparable wavenumbers, they exhibit different degrees of branching. The deviation in branching can be attributed to the intracycle strain hardening behavior seen at low CNT loadings in PDMS composites containing fumed silica. The study provides insights into the interactions occurring between CNTs and fumed silica in PDMS composites and highlights the significance of analyzing rheological parameters that are relevant at the high strains and strain rates experienced during roll coating, advancing our understanding of ribbing stability in yield stress fluids.

Thermal depolarization in poling-induced piezoelectric materials is defined as the disappearance of remanent polarization at a so-called depolarization temperature. A thermally stimulated depolarization current (TSDC) measurement is most widely used for examining depolarization as a function of temperature. TSDC results in the literature commonly show a gradual reduction of polarization even below depolarization temperature (Td). However, no degradation happens when thermal heat treatments are conducted below Td, meaning that the apparent reduction in polarization measured by TSDC is sure to be an artifact. Here, we demonstrate that such artifact is unavoidable during TSDC measurements and propose a method to circumvent it. This strategy was manifested on TSDC data collected from a relaxor ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) single crystals.

Heterogeneous ribbed and non-ribbed carbon nanotube (CNT)-PDMS thin-film systems manufactured by largescale rolling exhibit large-strain and high strain-rate characteristics with favorable surface behaviors, such as superhydrophobicity and drag reduction. However, it is not well understood how the multi-phase microstructure and material properties of non-ribbed thin-films are related to the surface material behavior and fracture. Hence, the objective of this investigation is to characterize the large-strain mechanical behavior and the microstructure of various CNT-PDMS compositions to understand how the CNT loading, agglomeration, distribution, and orientation affect the mechanical behavior and fracture of CNT-PDMS unribbed systems. Non-ribbed thin tensile testing specimens were fabricated for neat PDMS and CNT-PDMS with different weight CNT distributions to understand non-ribbed behavior. The ultimate strain, strength, and global stress-strain behavior were obtained by uniaxial mechanical testing. Scanning electron microscopy (SEM) of the fracture surface was also obtained for each sample to analyze the microstructure and relate the damage mode to the different weight distributions. Based on these experimental measurements and observations, large-strain, hyperelastic and hyper-viscoelastic material models were used to characterize the material behavior. The hyper-viscoelastic material model was shown to provide the most accurate material description of the thin-film behavior of the viscoelastic PDMS with the high-strength CNTs.

This article demonstrates design guidelines and development of a novel 3-D heterogeneous integration (3-DHI) thin glass substrate-based half-bridge switching power module for future onboard CPU, transceivers, and so on, power delivery applications. Due to extreme space constraints in onboard power supply applications, this design will support switching frequencies of >50 MHz with power levels of >30 W. To illustrate the capabilities of this module, the detailed ANSYS finite element analysis (FEA) analysis was carried out through thermomechanical and electromagnetic simulations. Extracting thermals is a major limitation factor in a compact layout. Hence, a thermal via density and substrate thickness parametric study was conducted, and effects on the integrity of the mechanical structure were verified through the simulation-based stress analysis. Finally, to switch at very high frequencies, the power and signal loop interconnects were routed through a thin glass substrate to achieve ultralow-power and gate loop parasitics. Two significant contributions demonstrate stacking various component layers in a half-bridge power stage and system-level packaging in a vertical profile.

This study investigates the micro-topographic surfaces as a benign anti-fouling/fouling-release method. The bio-inspired engineered surfaces were manufactured by controlling the viscoelastic instabilities of carbon nanotubes (CNTs) and polydimethylsiloxane (PDMS) nanocomposites using a customized, scalable two-roll coating process. The effects of manufacturing conditions, i.e., roller speed and roller radius-to-gap ratio, on surface properties, such as Wenzel roughness factor, peak density, water contact angle, and the tensile testing of the nanocomposite, were studied. The results showed that decreasing roller gap distance would significantly increase the hydrophobicity of the samples. Moreover, a positive correlation was observed between surface peak density and roughness factor. A textured sample was manufactured that significantly outperformed the non-textured CNT-PDMS, indicating a correlation between surface roughness and diatom attachment density. The dynamic diatom attachment assay showed up to 35% reduction in surface coverage of textured samples by the Navicula perminuta diatom compared to the non-textured CNT-PDMS control samples.

This study investigates the electrical properties of Pb(Mg1/3Nb2/3)-PbTiO3 (PMN-PT) single crystals subjected to corona poling (CorP) compared to direct current poling (DCP) and alternating current poling (ACP) methods. The results revealed the superiority of CorP in terms of polarization retention and softening. The corona-poled sample demonstrated a higher depolarization temperature (T-d similar to 100 celcius) than DCP or ACP methods (T-d similar to 90 celcius), indicating improved polarization stability at elevated temperatures. Furthermore, lowering of the coercive field (EC) in CorP samples suggests CorP makes the materials electrically softer. These advantages stem from the noncontact nature of the CorP method, which minimizes the risk of localized dielectric breakdown, and ensures a uniform electric field distribution. This work sheds a light on the potential of CorP as a promising technique for enhancing the electrical performance of materials in piezoelectric applications.