@article{miller_cabral_dickey_lebeau_reich_2021, title={Accounting for Location Measurement Error in Imaging Data With Application to Atomic Resolution Images of Crystalline Materials}, volume={4}, ISSN={["1537-2723"]}, url={https://app.dimensions.ai/details/publication/pub.1136536111}, DOI={10.1080/00401706.2021.1905070}, abstractNote={Scientists use imaging to identify objects of interest and infer properties of these objects. The locations of these objects are often measured with error, which when ignored leads to biased parameter estimates and inflated variance. Current measurement error methods require an estimate or knowledge of the measurement error variance to correct these estimates, which may not be available. Instead, we create a spatial Bayesian hierarchical model that treats the locations as parameters, using the image itself to incorporate positional uncertainty. We lower the computational burden by approximating the likelihood using a noncontiguous block design around the object locations. We use this model to quantify the relationship between the intensity and displacement of hundreds of atom columns in crystal structures directly imaged via scanning transmission electron microscopy (STEM). Atomic displacements are related to important phenomena such as piezoelectricity, a property useful for engineering applications like ultrasound. Quantifying the sign and magnitude of this relationship will help materials scientists more precisely design materials with improved piezoelectricity. A simulation study confirms our method corrects bias in the estimate of the parameter of interest and drastically improves coverage in high noise scenarios compared to non-measurement error models.}, number={1}, journal={TECHNOMETRICS}, author={Miller, Matthew J. and Cabral, Matthew J. and Dickey, Elizabeth C. and LeBeau, James M. and Reich, Brian J.}, year={2021}, month={Apr} }
 @article{nozariasbmarz_dycus_cabral_flack_krasinski_lebeau_vashaee_2021, title={Efficient self-powered wearable electronic systems enabled by microwave processed thermoelectric materials}, volume={283}, ISSN={["1872-9118"]}, DOI={10.1016/j.apenergy.2020.116211}, abstractNote={The integrated body sensor networks are expected to dominate the future of healthcare, making a critical paradigm shift that will support people in the comfort and security of their own homes. Thermoelectric generators, in this regard, can play a crucial role as they can steadily generate electricity from body heat and enable self-powered wearable or implantable medical, health, and sports devices. This work provides a comprehensive analysis of the operation and the optimization of wearable thermoelectric generators under different human body conditions. Thermoelectric design principles, wearable system considerations, and a novel method to synthesize the materials specially designed for body heat harvesting are presented. The limitations of the materials and systems for wearable applications are deliberated in detail, and the feasibility of eliminating the heatsink for enhancing body comfort is examined. N-type Bi2Te3-xSex was synthesized using a novel approach based on field-induced decrystallization by microwave radiation to achieve the optimum properties. This method resulted in amorphous-crystalline nanocomposites with simultaneously large thermopower and small thermal conductivity around the body temperature. Thermoelectric generators were fabricated from the optimized materials and packaged in flexible elastomers. The devices generated up to 150% higher voltage and 600% more power on the body compared to the commercial ones and, so far, are the best in class for body heat harvesting in wearable applications.}, journal={APPLIED ENERGY}, author={Nozariasbmarz, Amin and Dycus, J. Houston and Cabral, Matthew J. and Flack, Chloe M. and Krasinski, Jerzy S. and LeBeau, James M. and Vashaee, Daryoosh}, year={2021}, month={Feb} }
 @article{otonicar_bradesko_fulanovic_kos_ursic_bencan_cabral_henriques_jones_riemer_et al._2020, title={Connecting the Multiscale Structure with Macroscopic Response of Relaxor Ferroelectrics}, volume={30}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.202006823}, abstractNote={Abstract Lead‐based relaxor ferroelectrics are characterized by outstanding piezoelectric and dielectric properties, making them useful in a wide range of applications. Despite the numerous models proposed to describe the relation between their nanoscale polar structure and the large properties, the multiple contributions to these properties are not yet revealed. Here, by combining atomistic and mesoscopic‐scale structural analyses with macroscopic piezoelectric and dielectric measurements across the (100– x )Pb(Mg 1/3 Nb 2/3 )O 3 – x PbTiO 3 (PMN– x PT) phase diagram, a direct link is established between the multiscale structure and the large nonlinear macroscopic response observed in the monoclinic PMN‐ x PT compositions. The approach reveals a previously unrecognized softening effect, which is common to Pb‐based relaxor ferroelectrics and arises from the displacements of low‐angle nanodomain walls, facilitated by the nanoscale polar character and lattice strain disorder. This comprehensive comparative study points to the multiple, distinct mechanisms that are responsible for the large piezoelectric response in relaxor ferroelectrics.}, number={52}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Otonicar, Mojca and Bradesko, Andraz and Fulanovic, Lovro and Kos, Tomaz and Ursic, Hana and Bencan, Andreja and Cabral, Matthew J. and Henriques, Alexandra and Jones, Jacob L. and Riemer, Lukas and et al.}, year={2020}, month={Dec} }
 @article{pokharel_ramaswamy_devkota_parakh_dawkins_penn_cabral_reynolds_iyer_2020, title={Epitaxial High-Yield Intrinsic and Te-Doped Dilute Nitride GaAsSbN Nanowire Heterostructure and Ensemble Photodetector Application}, volume={2}, ISSN={["2637-6113"]}, DOI={10.1021/acsaelm.0c00450}, abstractNote={Band gap engineering of GaAsSbN nanowires (NWs) grown by Ga-assisted molecular beam epitaxy and demonstration of a Te-doped axial GaAsSbN NW-based Schottky barrier photodetector on p-Si (111) in the near-infrared region are reported. Stringent control on NW nucleation conditions, stem growth duration, and NW exposure to the N-plasma were found to be critical for the successful growth of high-quality dilute nitride quaternary GaAsSbN NWs in the axial configuration. Planar defect-free structures were realized with room temperature photoluminescence (PL) characteristics, revealing reduced N-induced point defects and nonradiative recombination centers. N incorporation in the dilute nitride NWs was ascertained from PL and Raman spectral mode shifts and shapes and weak temperature-dependent PL peak energy. The advantage of Te-doping in dilute nitride NWs using a GaTe captive source is the compensation of point defects, as evidenced by a significant improvement in PL characteristics, Raman mode shifts, and spectral shape, with improved photodetector device performance relative to intrinsic dilute nitride NWs. Te-doped GaAsSbN NW Schottky-based photodetectors have been demonstrated on both single and ensemble configurations with a resultant responsivity of 5 A/W at 860 nm and 3800 A/W at 1100, respectively. Detectivity of 3.2 × 1010 Jones was achieved on the Te-doped ensemble NW device. The findings presented in this work showcase prospects for rich band gap engineering using doped GaAsSbN NWs for near-infrared region device applications.}, number={9}, journal={ACS APPLIED ELECTRONIC MATERIALS}, author={Pokharel, Rabin and Ramaswamy, Priyanka and Devkota, Shisir and Parakh, Mehul and Dawkins, Kendall and Penn, Aubrey and Cabral, Matthew and Reynolds, Lewis and Iyer, Shanthi}, year={2020}, month={Sep}, pages={2730–2738} }
 @article{nozariasbmarz_suarez_dycus_cabral_lebeau_ozturk_vashaee_2020, title={Thermoelectric generators for wearable body heat harvesting: Material and device concurrent optimization}, volume={67}, ISSN={["2211-3282"]}, DOI={10.1016/j.nanoen.2019.104265}, abstractNote={Body heat harvesting systems based on thermoelectric generators (TEGs) can play a significant role in wearable electronics intended for continuous, long-term health monitoring. However, to date, the harvested power density from the body using TEGs is limited to a few micro-watts per square centimeter, which is not sufficient to turn on many wearables. The thermoelectric materials research has been mainly focused on enhancing the single parameter zT, which is insufficient to meet the requirements for wearable applications. To develop TEGs that work effectively in wearable devices, one has to consider the material, device, and system requirements concurrently. Due to the lack of an efficient heatsink and the skin thermal resistance, a key challenge to achieving this goal is to design systems that maximize the temperature differential across the TEG while not compromising the body comfort. This requires favoring approaches that deliver the largest possible device thermal resistance relative to the external parasitic resistances. Therefore, materials with low thermal conductivity are critically important to maximize the temperature gradient. Also, to achieve a high boost converter efficiency, wearable TEGs need to have the highest possible output voltage, which calls for a high Seebeck coefficient. At the device level, dimensions of the legs (length versus the base area) and fill factor are both critical parameters to ensure that the parasitic thermal resistances are again negligible compared to the resistance of the module itself. In this study, the concurrent impact of material and device parameters on the efficiency of wearable TEGs is considered. Nanocomposite thermoelectric materials based on bismuth telluride alloys were synthesized using microwave processing and optimized to meet the requirements of wearable TEGs. Microwave energy decrystallized the material leading to a strong reduction of the thermal conductivity while maintaining a high zT at the body temperature. A comprehensive quasi-3D analytical model was developed and used to optimize the material and device parameters. The nanocomposite TEG produced 44 μW/cm2 under no air flow condition, and 156.5 μW/cm2 under airflow. In comparison to commercial TEGs tested under similar conditions, the nanocomposite based TEGs exhibited 4–7 times higher power density on the human body depending on the convective cooling conditions.}, journal={NANO ENERGY}, author={Nozariasbmarz, Amin and Suarez, Francisco and Dycus, J. Houston and Cabral, Matthew J. and LeBeau, James M. and Ozturk, Mehmet C. and Vashaee, Daryoosh}, year={2020}, month={Jan} }
 @article{li_cabral_xu_cheng_dickey_lebeau_wang_luo_taylor_hackenberger_et al._2019, title={Giant piezoelectricity of Sm-doped Pb(Mg1/3Nb2/3)O-3-PbTiO3 single crystals}, volume={364}, ISSN={["1095-9203"]}, url={https://doi.org/10.1126/science.aaw2781}, DOI={10.1126/science.aaw2781}, abstractNote={High-performance piezoelectrics benefit transducers and sensors in a variety of electromechanical applications. The materials with the highest piezoelectric charge coefficients (d33) are relaxor-PbTiO3 crystals, which were discovered two decades ago. We successfully grew Sm-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 (Sm-PMN-PT) single crystals with even higher d33 values ranging from 3400 to 4100 picocoulombs per newton, with variation below 20% over the as-grown crystal boule, exhibiting good property uniformity. We characterized the Sm-PMN-PT on the atomic scale with scanning transmission electron microscopy and made first-principles calculations to determine that the giant piezoelectric properties arise from the enhanced local structural heterogeneity introduced by Sm3+ dopants. Rare-earth doping is thus identified as a general strategy for introducing local structural heterogeneity in order to enhance the piezoelectricity of relaxor ferroelectric crystals.}, number={6437}, journal={SCIENCE}, publisher={American Association for the Advancement of Science (AAAS)}, author={Li, Fei and Cabral, Matthew J. and Xu, Bin and Cheng, Zhenxiang and Dickey, Elizabeth C. and LeBeau, James M. and Wang, Jianli and Luo, Jun and Taylor, Samuel and Hackenberger, Wesley and et al.}, year={2019}, month={Apr}, pages={264-+} }
 @article{kang_floyd_lowum_cabral_dickey_maria_2019, title={Mechanism studies of hydrothermal cold sintering of zinc oxide at near room temperature}, volume={102}, ISSN={0002-7820 1551-2916}, url={http://dx.doi.org/10.1111/JACE.16340}, DOI={10.1111/jace.16340}, abstractNote={Zinc oxide densification mechanisms occurring during the cold sintering process (CSP) are examined by investigating specifically the effects of ion concentration in solution, temperature, pressure, and die sealing. The experiments suggest that mass transport through solution is a primary densification mechanism and that either a pre-loaded solution or grain dissolution can supply migrating ions. Additionally, results indicate cold sintering zinc oxide requires a critical pressure value, above which densification is relatively pressure independent under the majority of process conditions. This critical pressure is related to thermal expansion of the liquid and determines the uniaxial pressure threshold for densification. The data supports a three-stage interpretation of cold sintering, which includes quick compaction, grain rearrangement, and dissolution-reprecipitation events. Further, it is observed that under the lowest temperature conditions a net decrease in particle size can occur during the cold sintering process.}, number={8}, journal={Journal of the American Ceramic Society}, publisher={Wiley}, author={Kang, Xiaoyu and Floyd, Richard and Lowum, Sarah and Cabral, Matthew and Dickey, Elizabeth and Maria, Jon‐Paul}, year={2019}, month={Feb}, pages={4459–4469} }
 @article{cabral_zhang_dickey_lebeau_2018, title={Gradient chemical order in the relaxor Pb(Mg1∕3Nb2∕3)O3}, volume={112}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.5016561}, DOI={10.1063/1.5016561}, abstractNote={Here, we apply aberration-corrected scanning transmission electron microscopy to quantify chemical ordering in the relaxor Pb(Mg1∕3Nb2∕3)O3 (PMN). We find that contrary to the prevailing model of a binary distribution of chemically ordered regions within a disordered matrix, the degree of ordering smoothly varies within an ordered domain and approaches a minimum at anti-phase boundaries. These results provide direct insight into the nature of cation ordering in this important prototypical relaxor material.}, number={8}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Cabral, Matthew J. and Zhang, Shujun and Dickey, Elizabeth C. and LeBeau, James M.}, year={2018}, month={Feb}, pages={082901} }
 @article{nozariasbmarz_roy_zamanipour_dycus_cabral_lebeau_krasinski_vashaee_2016, title={Comparison of thermoelectric properties of nanostructured Mg2Si, FeSi2, SiGe, and nanocomposites of SiGe-Mg2Si, SiGe-FeSi2}, volume={4}, ISSN={["2166-532X"]}, DOI={10.1063/1.4966138}, abstractNote={Thermoelectric properties of nanostructured FeSi2, Mg2Si, and SiGe are compared with their nanocomposites of SiGe–Mg2Si and SiGe–FeSi2. It was found that the addition of silicide nanoinclusions to SiGe alloy maintained or increased the power factor while further reduced the thermal conductivity compared to the nanostructured single-phase SiGe alloy. This resulted in ZT enhancement of Si0.88Ge0.12–FeSi2 by ∼30% over the broad temperature range of 500-950 °C compared to the conventional Si0.80Ge0.20 alloy. The Si0.88Ge0.12–Mg2Si nanocomposite showed constantly increasing ZT versus temperature up to 950 °C (highest measured temperature) reaching ZT ∼ 1.3. These results confirm the concept of silicide nanoparticle-in-SiGe-alloy proposed earlier by Mingo et al. [Nano Lett. 9, 711–715 (2009)].}, number={10}, journal={APL MATERIALS}, author={Nozariasbmarz, Amin and Roy, Palash and Zamanipour, Zahra and Dycus, J. Houston and Cabral, Matthew J. and LeBeau, James M. and Krasinski, Jerzy S. and Vashaee, Daryoosh}, year={2016}, month={Oct} }