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1. The Thermoelectric Properties of Bismuth Telluride

   https://doi.org/10.1002/aelm.201800904  

   Witting, Ian T.; Chasapis, Thomas C.; Ricci, Francesco; Peters, Matthew; Heinz, Nicholas A.; Hautier, Geoffroy; Snyder, G. Jeffrey (April 2019, Advanced Electronic Materials)

   Abstract Bismuth telluride is the working material for most Peltier cooling devices and thermoelectric generators. This is because Bi₂Te₃(or more precisely its alloys with Sb₂Te₃for p‐type and Bi₂Se₃for n‐type material) has the highest thermoelectric figure of merit,zT, of any material around room temperature. Since thermoelectric technology will be greatly enhanced by improving Bi₂Te₃or finding a superior material, this review aims to identify and quantify the key material properties that make Bi₂Te₃such a good thermoelectric. The largezTcan be traced to the high band degeneracy, low effective mass, high carrier mobility, and relatively low lattice thermal conductivity, which all contribute to its remarkably high thermoelectric quality factor. Using literature data augmented with newer results, these material parameters are quantified, giving clear insight into the tailoring of the electronic band structure of Bi₂Te₃by alloying, or reducing thermal conductivity by nanostructuring. For example, this analysis clearly shows that the minority carrier excitation across the small bandgap significantly limits the thermoelectric performance of Bi₂Te₃, even at room temperature, showing that larger bandgap alloys are needed for higher temperature operation. Such effective material parameters can also be used for benchmarking future improvements in Bi₂Te₃or new replacement materials. 

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2. Atomic doping to enhance the p-type behavior of BiFeO ₃ photoelectrodes for solar H ₂ O ₂ production

   https://doi.org/10.1039/d4ta03191a  

   Seo, Daye; Grieder, Andrew; Radmilovic, Andjela; Alamudun, Sophya F; Yuan, Xin; Ping, Yuan; Choi, Kyoung-Shin (August 2024, Journal of Materials Chemistry A)

   Na-doped BiFeO₃demonstrates an enhanced p-type behavior compared to p-type BiFeO₃prepared without extrinsic dopants, and Na-doped BiFeO₃can serve as a photocathode for solar O₂reduction to H₂O₂when coupled with Ag nanoparticle catalysts. 

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3. Calibration of the Solid‐State Nuclear Magnetic Resonance Search for Axion‐Like Dark Matter

   https://doi.org/10.1002/andp.202300252  

   Winter, Andrew J.; Marić, Tanja; Balabanova, Viktoriya A.; Ádám, János; Randall, Glenn; Wickenbrock, Arne; Jackson Kimball, Derek F.; Budker, Dmitry; Sushkov, Alexander O. (November 2023, Annalen der Physik)

   Abstract Calibration of nuclear‐magnetic‐resonance‐based searches for axion‐like dark matter can be performed by free induction decay (FID) measurements. This manu‐ script describes FID experiments on several solid materials, motivated by the Cosmic Axion Spin Precession Experiment (CASPEr) program. Experiments with²⁰⁷Pb nuclear spins in ferroelectrics, lead magnesium niobate‐lead titanate (PbMg_1/3Nb_2/3O₃) (PbTiO₃)_1/3(PMN‐PT) and lead zirconium titante PbZr_0.52Ti_0.48O₃(PZT) are directly relevant to the CASPEr‐electric search for the electric dipole moment interaction of axion‐like dark matter. Experiments with³¹P nuclear spins in gadolinium‐doped hydroxypyromorphite Pb_4.95Gd_0.05(PO₄)₃OH (HPM:Gd) are used for apparatus calibration. The measurements characterized the nuclear spin ensemble coherence time and the magnetic resonance detection sensitivity for these samples. Calibration is performed using small tip‐angle pulses. 

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4. Formation of large low shear velocity provinces through the decomposition of oxidized mantle

   https://doi.org/10.1038/s41467-021-22185-1  

   Wang, Wenzhong; Liu, Jiachao; Zhu, Feng; Li, Mingming; Dorfman, Susannah M.; Li, Jie; Wu, Zhongqing (March 2021, Nature Communications)

   Abstract Large Low Shear Velocity Provinces (LLSVPs) in the lowermost mantle are key to understanding the chemical composition and thermal structure of the deep Earth, but their origins have long been debated. Bridgmanite, the most abundant lower-mantle mineral, can incorporate extensive amounts of iron (Fe) with effects on various geophysical properties. Here our high-pressure experiments and ab initio calculations reveal that a ferric-iron-rich bridgmanite coexists with an Fe-poor bridgmanite in the 90 mol% MgSiO₃–10 mol% Fe₂O₃system, rather than forming a homogeneous single phase. The Fe³⁺-rich bridgmanite has substantially lower velocities and a higherV_P/V_Sratio than MgSiO₃bridgmanite under lowermost-mantle conditions. Our modeling shows that the enrichment of Fe³⁺-rich bridgmanite in a pyrolitic composition can explain the observed features of the LLSVPs. The presence of Fe³⁺-rich materials within LLSVPs may have profound effects on the deep reservoirs of redox-sensitive elements and their isotopes. 

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5. Empirical Insights Into the Fate of Ammonia in Western U.S. Wildfire Smoke Plumes

   https://doi.org/10.1029/2020JD033730  

   Lindaas, Jakob; Pollack, Ilana B.; Calahorrano, Julieta Juncosa; O'Dell, Katelyn; Garofalo, Lauren A.; Pothier, Matson A.; Farmer, Delphine K.; Kreidenweis, Sonia M.; Campos, Teresa; Flocke, Frank; et al (June 2021, Journal of Geophysical Research: Atmospheres)

   Abstract Wildfires are a major source of gas‐phase ammonia (NH₃) to the atmosphere. Quantifying the evolution and fate of this NH₃is important to understanding the formation of secondary aerosol in smoke and its accompanying effects on radiative balance and nitrogen deposition. Here, we use data from the Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE‐CAN) to add new empirical constraints on the e‐folding loss timescale of NH₃and its relationship with particulate ammonium (pNH₄) within wildfire smoke plumes in the western U.S. during summer 2018. We show that the e‐folding loss timescale of NH₃with respect to particle‐phase partitioning ranges from ∼24 to ∼4000 min (median of 55 min). Within these same plumes, oxidation of nitrogen oxides is observed concurrent with increases in the fraction ofpNH₄in each plume sampled, suggesting that formation of ammonium nitrate (NH₄NO₃) is likely. We find wide variability in how close ourin situmeasurements of NH₄NO₃are to those expected in a dry thermodynamic equilibrium, and find that NH₄NO₃is most likely to form in fresh, dense smoke plumes injected at higher altitudes and colder temperatures. In chemically older smoke we observe correlations between both the fraction ofpNH₄and the fraction of particulate nitrate (pNO₃) in the aerosol with temperature, providing additional evidence of the presence of NH₄NO₃and the influence of injection height on gas‐particle partitioning of NH₃. 

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