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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 289 records · Page 16

Correlating Crystallographic Orientation and Ferroic Properties of Twin Domains in Metal Halide Perovskites

Metal halide perovskite (MHP) solar cells have attracted worldwide research interest. Although it has been well established that grain, grain boundary, and grain facet affect MHPs optoelectronic properties, less is known about subgrain structures. Recently, MHP twin stripes, a subgrain feature, have stimulated extensive discussion due to the potential for both beneficial and detrimental effects of ferroelectricity on optoelectronic properties. Furthermore, connecting the ferroic behavior of twin stripes in MHPs with crystal orientation will be a vital step to understand the ferroic nature and the effects of twin stripes. In this work, we studied the crystallographic orientation and ferroic properties of CH 3 NH 3 PbI 3 twin stripes, using electron backscatter diffraction (EBSD) and advanced piezoresponse force microscopy (PFM), respectively. Using EBSD, we discovered that the orientation relationship across the twin walls in CH 3 NH 3 PbI 3 is a 90° rotation about ($\bar{11}0$), with the (030) and (111) directions parallel to the direction normal to the surface. By careful inspection of CH 3 NH 3 PbI 3 PFM results including in-plane and out-of-plane PFM measurements, we demonstrate some nonferroelectric contributions to the PFM responses of this CH 3 NH 3 PbI 3 sample, suggesting that the PFM signal in this CH 3 NH 3 PbI 3 sample is affected by nonferroelectric and nonpiezoelectric forces. If there is piezoelectric response, it is below the detection sensitivity of our interferometric displacement sensor PFM (<0.615 pm/V). Overall, this work offers an integrated picture describing the crystallographic orientations and the origin of PFM signal of MHPs twin stripes, which is critical to understanding the ferroicity in MHPs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Strongly temperature dependent ferroelectric switching in AlN, Al 1-x Sc x N, and Al 1-x B x N thin films

This manuscript reports the temperature dependence of ferroelectric switching in Al 0.84 Sc 0.16 N, Al 0.93 B 0.07 N, and AlN thin films. Polarization reversal is demonstrated in all compositions and is strongly temperature dependent. Between room temperature and 300 °C, the coercive field drops by almost 50% in all samples, while there was very small temperature dependence of the remanent polarization value. Furthermore, over this same temperature range, the relative permittivity increased between 5% and 10%. Polarization reversal was confirmed by piezoelectric coefficient analysis and chemical etching. Applying intrinsic/homogeneous switching models produces nonphysical fits, while models based on thermal activation suggest that switching is regulated by a distribution of pinning sites or nucleation barriers with an average activation energy near 28 meV.

36 MATERIALS SCIENCE↗

Engineering local strain for single-atom nuclear acoustic resonance in silicon

Mechanical strain plays a key role in the physics and operation of nanoscale semiconductor systems, including quantum dots and single-dopant devices. In this report we describe the design of a nanoelectronic device, where a single nuclear spin is coherently controlled via nuclear acoustic resonance (NAR) through the local application of dynamical strain. The strain drives spin transitions by modulating the nuclear quadrupole interaction. We adopt an AlN piezoelectric actuator compatible with standard silicon metal–oxide–semiconductor processing and optimize the device layout to maximize the NAR drive. We predict NAR Rabi frequencies of order 200 Hz for a single 123Sb nucleus in a wide region of the device. Spin transitions driven directly by electric fields are suppressed in the center of the device, allowing the observation of pure NAR. Using electric field gradient-elastic tensors calculated by the density-functional theory, we extend our predictions to other high-spin group-V donors in silicon and to the isoelectronic 73Ge atom.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Strain transfer in porous multiferroic composites of CoFe 2 O 4 and PbZr x Ti 1- x O 3

This manuscript examines the mechanism of strain-coupling in a multiferroic composite of mesoporous cobalt ferrite (CFO), conformally filled with lead zirconate titanate (PZT). We find that when the composites are electrically poled, remanent strain from the piezoelectric PZT layer can be transferred to the magnetostrictive CFO layer. X-ray diffraction shows that this strain transfer is greatest in the most porous samples, in agreement with magnetometry measurements, which show the greatest change in sample saturation magnetization in the most porous samples. In conclusion, strain analysis shows that porosity both accommodates greater lattice strain and mitigates the effects of substrate clamping in thin film strain-coupled composites.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Investigations of room temperature multiferroic and magneto-electric properties of (1-Φ) PZTFT-Φ CZFMO particulate composites

Multiferroic composites consisting of a single-phase multiferroic [0.6(PbZr 0.53 Ti 0.47 O 3 )-0.4(PbFe 0.5 Ta 0.5 )O 3 ] as a matrix and a magnetostrictive phase (Co 0.6 Zn 0.4 Fe 1.7 Mn 0.3 O 4 ) dispersed in the matrix are fabricated via hybrid synthesis technique. The structure and surface morphology studies using x-ray diffraction and field emission scanning electron microscopy techniques indicate the formation of 3-0 type particulate composites. Coexistence of soft-magnetic behavior and ferroelectric characteristics are confirmed for composites from magnetization vs magnetic field (M–H) and polarization vs electric field (P–E) measurements, respectively. Magneto-dielectric (MD) measurement shows significant changes in the dielectric properties with the application of a magnetic field, indicating the existence of strong MD behavior. The biquadratic nature of magneto-electric (ME) coupling is described by the Landau free energy equation arising from the strain transfer at the interfaces between the constituent phases. The direct magneto-electric voltage coefficient measurement also confirms very strong coupling between ferroelectricity and magnetism and supports the strain-mediated magneto-electric effect in composites. The Φ = 0.3 composite exhibits the maximum ME coefficient of 20.72 mV/cm Oe with M S = 24.62 emu/g, H C = 59.66 Oe, and piezoelectric coefficient value d 33 = 19 pC/N. In conclusion, the strong magneto-electric effect along with low dielectric loss at room temperature in these composites suggests their suitability for multifunctional magneto-electric device applications such as magnetic sensors, etc.

36 MATERIALS SCIENCE↗

Thickness dependence of piezo-bimorph adaptive mirror bending

A new generation of adaptive x-ray optics (AXO) is being installed on high-coherent-flux x-ray beamlines worldwide to correct and control the optical wavefront with sub-nm precision. These ultra-smooth mirrors achieve high reflectivities at glancing angles of incidence and can be hundreds of mm long. One type of adaptive x-ray mirror relies on piezoelectric ceramic strips which are segmented into channels and actuated to induce local, longitudinal bending, generating one-dimensional shape changes in the mirror substrate. A recently described mirror model uses a three-layer geometry with parallel actuators on the front and back surfaces of a thicker mirror substrate. By analogy to a solved problem in the thermal actuation of a tri-metal strip, we show that the achievable bending radius varies approximately as the square of the substrate thickness. We provide an analytic solution and simulate bending using a finite-element model.

47 OTHER INSTRUMENTATION↗

An exploration of anomalous electrical noise in shocked cyclotrimethylenetrinitramine (RDX)-based explosives

Gas gun shock experiments on cyclotrimethylenetrinitramine (RDX)-based explosive compositions that employ embedded gauge particle velocity tracers have noted a significant amount of electrical noise when compared to other explosive formulations. This paper reexamines previously published embedded gauge data on Cyclotols (60–80 wt. % RDX) to quantify the electromagnetic behavior of these materials. The primary observation is a fourfold increase in the electrical noise when Cyclotols are shocked above 4.22 ± 0.08 GPa. Electromagnetic gauge noise is also observed within particle velocity traces in reactive growth and off-Hugoniot shocks, although at higher pressures than the direct shock case, suggesting a temperature- or kinetically dependent transition. In all cases, the electrical noise disappears upon detonation. By comparing with the static high-pressure phase diagram of RDX, we interpret this change in electromagnetic behavior to be a change in the RDX crystal structure to a piezoelectric phase, although it is uncertain whether the γ or ε phase is responsible for the observed behavior.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Monolithic AlScN/SiC phononic waveguides for scalable acoustoelectric and quantum devices

Unlike conventional surface acoustic wave devices, phononic waveguide systems enable higher circuit density and stronger strain and piezoelectric fields, making them promising for advanced acoustoelectric and quantum applications. One such material system for generating and guiding phonons at gigahertz frequencies is AlScN on SiC, which can be synthesized by sputter depositing AlScN directly onto SiC wafers. The AlScN on the SiC platform allows for tightly vertically-confined acoustic modes with high electromechanical coupling, high speed of sound, and simple fabrication of strip and rib waveguides. Until now, this system has only been studied as a slab waveguide platform, i.e., without any lateral waveguiding. Here, we demonstrate a two-dimensionally confined phononic architecture in AlScN on SiC that supports guided modes at 2.95 and 4.05 GHz. These modes exhibit strong electromechanical coupling coefficients (k 2 = 4.27%) and propagation losses on the order of 10 dB/mm. Furthermore, this architecture is well-suited for phononic routing and power-efficient active or nonlinear devices such as amplifiers, mixers, and oscillators, and is compatible with the integration of quantum systems, including vacancy centers, charge carriers, photons, and spins, either embedded in SiC or heterogeneously integrated on the surface.

Electrical components↗

Ferroelectricity of wurtzite Al 1−x Hf x N heterovalent alloys

Thin films of aluminum hafnium nitride (Al1−xHfxN) were synthesized via reactive magnetron sputtering for Hf contents up to x = 0.13. X-ray diffraction showed a single c-axis oriented wurtzite phase for all films. Hard x-ray photoelectron spectroscopy demonstrated homogeneous Al:Hf distribution through the thin films and confirmed their insulating character. A collection of complementary tests showed unambiguous polarization inversion, and thus ferroelectricity in multiple samples. Current density vs electric field hysteresis measurements showed distinct ferroelectric switching current peaks, the piezoelectric coefficient d 33,f,meas measured using a double beam laser interferometer (DBLI) showed a reversal in sign with similar magnitude, and anisotropic wet etching confirmed field-induced polarization inversion. This demonstrates the possibility of using tetravalent–and not just trivalent–alloying elements to enable ferroelectricity in AlN-based thin films, highlighting the compositional flexibility of ferroelectricity in wurtzites and greatly expanding the chemistries that can be considered for future devices.

36 MATERIALS SCIENCE↗

Magnetic state switching in FeGa microstructures

This work demonstrates that magnetoelectric composite heterostructures can be designed at the length scale of 10µms that can be switched from a magnetized state to a vortex state, effectively switching the magnetization off, using electric field induced strain. This was accomplished using thin film magnetoelectric heterostructures of Fe 81.4 Ga 18.6 on a single crystal (011) [Pb(Mg 1/3 Nb 2/3 )O 3 ] 0.68 -[PbTiO 3 ] 0.32 (PMN-32PT) ferroelectric substrate. Here, the heterostructures were tripped from a multi-domain magnetized state to a flux closure vortex state using voltage induced strain in a piezoelectric substrate. FeGa heterostructures were deposited on a Si-substrate for superconducting quantum interference device magnetometry characterization of the magnetic properties. The magnetoelectric coupling of a FeGa continuous film on PMN-32PT was characterized using a magneto optical Kerr effect magnetometer with bi-axial strain gauges, and magnetic multi-domain heterostructures were imaged using x-ray magnetic circular dichroism—photoemission electron microscopy during the transition to the vortex state. The domain structures were modelled using MuMax 3 , a micromagnetics code, and compared with observations. The results provide considerable insight into designing magnetoelectric heterostructures that can be switched from an ‘on’ state to an ‘off’ state using electric field induced strain.

36 MATERIALS SCIENCE↗

Roadmap on energy harvesting materials

Ambient energy harvesting has great potential to contribute to sustainable development and address growing environmental challenges. Converting waste energy from energy-intensive processes and systems (e.g. combustion engines and furnaces) is crucial to reducing their environmental impact and achieving net-zero emissions. Compact energy harvesters will also be key to powering the exponentially growing smart devices ecosystem that is part of the Internet of Things, thus enabling futuristic applications that can improve our quality of life (e.g. smart homes, smart cities, smart manufacturing, and smart healthcare). To achieve these goals, innovative materials are needed to efficiently convert ambient energy into electricity through various physical mechanisms, such as the photovoltaic effect, thermoelectricity, piezoelectricity, triboelectricity, and radiofrequency wireless power transfer. By bringing together the perspectives of experts in various types of energy harvesting materials, this Roadmap provides extensive insights into recent advances and present challenges in the field. Additionally, the Roadmap analyses the key performance metrics of these technologies in relation to their ultimate energy conversion limits. Building on these insights, the Roadmap outlines promising directions for future research to fully harness the potential of energy harvesting materials for green energy anytime, anywhere.

14 SOLAR ENERGY↗

Anomalous polarization reversal in strained thin films of CuIn⁢P 2 ⁢S 6

Strain-induced transitions of polarization reversal in thin films of a ferrielectric CuIn⁢P 2 ⁢S 6 (CIPS) with ideally conductive electrodes are explored using the Landau-Ginzburg-Devonshire approach with an eighth-order free energy expansion in polarization powers. Due to multiple potential wells, the height and position of which are temperature and strain dependent, the energy profiles of CIPS can flatten in the vicinity of the nonzero polarization states. Thereby, we reveal an unusually strong effect of a mismatch strain on the out-of-plane polarization reversal, hysteresis loop shape, dielectric susceptibility, and piezoelectric response of CIPS films. By varying the sign of the mismatch strain and its magnitude in a fairly narrow range, quasistatic hysteresisless paraelectric curves can transform into double, triple, and other types of pinched and single hysteresis loops. The strain effect on the polarization reversal is opposite, i.e., anomalous, in comparison with many other ferroelectric films, for which the out-of-plane remanent polarization and coercive field increase strongly for tensile strains and decrease or vanish for compressive strains. For definite values of temperature and mismatch strain, the low-frequency hysteresis loops of polarization may exhibit negative slope in a relatively narrow range of external field amplitude and frequency. The low-frequency susceptibility hysteresis loops, which correspond to the negative slope of polarization loops, contain only positive values, which can be giant in the entire range of field changes. In conclusion, the corresponding piezoresponse also reaches giant values, being maximal near coercive fields.

Dielectric properties↗

Structural, electronic, and polarization properties of YN and LaN

ScN has attracted great attention for its electronic properties and its ability to enhance polarization of AlN; however, its sister compounds, YN and LaN, remain much less studied. Here, we use first-principles calculations to evaluate YN and LaN in their cubic and hexagonal phases. Rocksalt YN and LaN are semiconductors, although we show that LaN differs from ScN and YN in having a direct band gap, which we attribute to its weaker p-p coupling. Both have low electron effective masses. In addition to their rocksalt structures, we evaluate the layered hexagonal and wurtzite phases of YN and LaN. For YN, the wurtzite phase cannot be stabilized, and hexagonal YN is higher in energy than rocksalt YN. In contrast, for LaN, the wurtzite phase is favored, and it is comparable in energy to rocksalt LaN. Wurtzite LaN has a polarization of 0.608 C/m 2 (referenced to the centrosymmetric layered hexagonal phase), and a high piezoelectric coefficient e 33 = 1.78 C/m 2 . Interestingly, we find that the polarization of wurtzite LaN may be reversible; we find a relatively small switching barrier of 0.06 eV per formula unit, offering the potential for its use as a ferroelectric. Since wurtzite LaN is closely lattice matched to InP, we investigate a heterostructure between (0001) wurtzite LaN and (111) zinc-blende InP, and find the polarization discontinuity would yield a bound charge of 1.3 × 10 14 e/cm 2 , offering the potential for novel electronic applications such as tunnel junctions. Furthermore, our results compare and contrast ScN, YN, and LaN, and highlight the potential of these materials for adoption in electronic and ferroelectric devices.

36 MATERIALS SCIENCE↗

Optimizing Sensor Count and Placement to Detect Bond Wire Lift-Offs and Surface Defects in High-Power IGBT Modules Using Low-Cost Piezo-Electric Resonators

This manuscript presents the most recent results and findings to identify bond wire lift-offs and surface defects in high-power isolated gate bipolar junction transistor (IGBT) modules. The authors of this manuscript formerly proposed a low-cost, piezoelectric resonator-based measurement unit to detect bond wire related degradation in larger IGBT modules. Since high-power IGBT modules are expensive, it was apparent that evaluating our proposed method by inducing controlled damage to fresh (new) IGBTs may not be cost-effective especially when multiple sets of data need to be captured by inducing damage to different levels. In order to overcome this limitation, IGBT bond wires have been mimicked using a 3D printed enclosure, a PCB, and copper wires with dimensions very closely resembling a real IGBT. Using this method, multiple test devices can be built at the cost of a real IGBT, and the proposed technique could be fine-tuned without damaging expensive, real IGBTs. Our recent findings can be used to determine real IGBT degradation and bond wire lift-offs using only two sensors, as opposed to six transducers used in the first iteration of the setup. In addition to optimizing the sensor count, we have also identified the best possible locations of these sensors by attempting multiple placements inside the IGBT casing.

condition monitoring↗

Piezo-Antenna: An Electromagnetic-Ultrasonic Data Transfer System

Electronic systems contained within sealed metallic enclosures, such as nuclear waste containers where wire penetration is not an option, require a through-wall data transfer technology to communicate. One such technology utilizes piezoelectric ultrasonic transducers to communicate through the barrier using elastic waves. Currently demonstrated ultrasonic through-wall data communication techniques have relied on having a direct interface with the ultrasonic transducers on either side. Here, this work studies the coupling of an antenna to such an ultrasonic communication system. A computationally efficient model of a piezobarrier ultrasonic communication system and antenna using a simplified antenna model and a transfer matrix piezobarrier model is utilized to perform a representative parameter space search. The system efficiency and bandwidth trends are shown for the system parameters as well as operating frequency. The tradeoff between efficiency and bandwidth is also presented. A system configuration within the parameter space is fabricated and demonstrated to achieve a data rate of up to 100 kb/s.

Antenna↗

3D printing of ceramics: Advantages, challenges, applications, and perspectives

Abstract 3D printing (3DP) technologies have transformed the processing of advanced ceramics for small‐scale and custom designs during the past three decades. Simple and complex parts are designed and manufactured using 3DP technologies for structural, piezoelectric, and biomedical applications. Manufacturing simple or complex geometries or one‐of‐a‐kind components without part‐specific tooling saves significant time and creates new applications for advanced ceramic materials. Although development and innovations in 3DP of ceramics are far behind compared with metals or polymers, with the availability of different commercial machines in recent years for 3DP of ceramics, exponential growth is expected in this field in the coming decade. This article details various 3DP technologies for advanced ceramic materials, their advantages and challenges for manufacturing parts for various applications, and perspectives on future directions. We envision this work will be helpful to advanced ceramic researchers in industry and academia who are using different 3DP processes in the coming days.

36 MATERIALS SCIENCE↗

TEAMER: Electrically Engaged Undulation System for Unmanned Underwater Vehicles

This TEAMER RFTS 1 (Request for Technical Support) project supported the flume tank testing of a long range, high endurance unmanned underwater vehicle (UUV) to monitor maritime space. Today, battery-powered remotely operated vehicles (ROVs) lack the duration to make persistent, wide-area data collection possible.The proposed solution, an Electrically Engaged UnduLation (EEL) drone, can sustain missions for longer duration through hydrodynamic energy harvesting. Power is provisioned via the piezoelectric effect, a material-led phenomenon that converts applied stress into electricity. The EEL subsystems include power, propulsion, navigation, ballast, telemetry, and instrumentation. By mimicking the gait of aquatic eels, EEL can counter currents during maneuvering and level-flight. The identified opportunity is in the future capability of extreme endurance UUVs in swarms. The specific goal for the EEL development is to expand the spatio-temporal coverage of the existing ocean observation mission by overcoming significant challenges of autonomous robotics. Some of the challenges presented include novel compliant mechanism for robust actuation, bio-inspired design to emulate efficient locomotion, smart material-based energy harvesting for sustained power, and swarming architecture through enabled autonomy.

16 TIDAL AND WAVE POWER↗