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The realization of remarkable thermoelectric (TE) properties in a novel single-crystalline quantum material is a topic of prime interest in the field of thermoelectricity. It necessitates a proper understanding of transport properties under magnetic field and magnetic properties at low field. We report polarized Raman spectroscopic study, TE properties, and magneto-resistance (MR) along with magnetic characterization of single-crystalline Bi2Se3. Polarized Raman spectrum confirms the strong polarization effect of A 1 g 1 and A 1 g 2 phonon modes, which verifies the anisotropic nature of the Bi2Se3 single crystal. Magnetization measurement along the in-plane direction of single crystal divulges a cusp-like paramagnetic response in susceptibility plot, indicating the presence of topological surface states (TSSs) in the material. In-depth MR studies performed in different configurations also confirm the presence of anisotropy in the single-crystalline Bi2Se3 sample. A sharp rise in MR value near zero magnetic field and low-temperature regime manifests a weak anti-localization (WAL) effect, depicting the quantum origin of the conductivity behavior at low temperature. Moreover, in-plane magneto-conductivity data at low-temperature (up to 5 K) and low-field region (≤15 kOe) confirm the dominance of the WAL effect (due to TSS) with a negligible bulk contribution. Quantum oscillation (SdH) in magneto-transport data also exhibits the signature of TSS. Additionally, an exceptional TE power factor of ∼950 μW m−1 K−2 at 300 K is achieved, which is one of the highest values reported for pristine Bi2Se3. Our findings pave the way for designing single crystals, which give dual advantages of being a good TE material along with a topological insulator bearing potential application. [ABSTRACT FROM AUTHOR]

Boron doped tin oxide nanocrystals with tetragonal symmetry (space group: P42/mnm) were prepared by sol-gel route using three different polyhydroxy alcohols like starch, glycerol and poly vinyl alcohol (PVA). Morphological and structural properties were studied for these samples by using scanning electron microscopy, X-ray powder diffraction, Raman spectroscopy and Fourier transform infrared spectroscopy. The morphology of the as-prepared SnO2 sample is dependent on the polyhydroxy alcohol used for preparation in sol-gel method and is evident from scanning electron microscopy and X-ray powder diffraction line profile analysis. Detailed characterization for the effects of lower particle dimensions has been explored and existence of oxygen vacancies has been observed for all the samples. Paracrystalline disorder was observed in the SnO2 sample prepared in glycerol medium. Boron is present as interstitial BO4 and BO3 unit in crystal lattice. The anti-bacterial efficacy of the boron doped SnO2 samples is dependent on the crystallite morphology [ABSTRACT FROM AUTHOR]

A study of Nd based cuprate francisite (NdCufr) is fascinating due to the presence of competing magnetic interactions in this geometrically frustrated layered compound, and Ni doping helps in tailoring these interactions. Here, Ni doped NdCufr is synthesized to compare its magnetic properties with pristine and Co doped NdCufr. Structural (x-ray diffraction, XRD), electronic (x-ray absorption near edge spectroscopy, XANES, and extended x-ray absorption fine structure, EXAFS), and magnetic (temperature dependent magnetization, M–T; field dependent magnetization, M–B) properties are investigated. The XRD, XANES, and EXAFS measurement data show a perfect crystal structure and confirm the merit of doping. A comprehensive comparison for examining the role of Co and Ni in modulation with ferromagnetic–antiferromagnetic interaction strength is presented. A crucial interplay of intra- and interlayer couplings, along with f–d interaction, effectively describes the tuning of Neel temperature (TN) and M–B. Detailed processes of field induced metamagnetic transition around the spin-flip ordering field (BSF), which is equal to that of the critical field (BC) and doping induced ferromagnetism, are addressed considering the relative spin orientations of magnetic elements and energy level splitting schemes, respectively. It is found that the studied compound is magnetically superior to the compared compounds. [ABSTRACT FROM AUTHOR]

Climate change is known to cause alterations in weather patterns and disturb the natural equilibrium. Changes in climatic conditions lead to increased environmental stress on embankments, which can result in slope failures. Due to wetting–drying cycles, expansive clayey soil often swells and shrinks, and matric suction is a major factor that controls the behavior. Increased temperature accelerates soil evaporation and drying, which can cause desiccation cracks, while precipitation can rapidly reduce soil shear strength. Desiccated slopes on embankments built with such soils can cause surficial slope failures after intense precipitation. This study used slope stability analysis to quantify how climate-change-induced extreme weather affects embankments. Historic extreme climatic events were used as a baseline to estimate future extremes. CMIP6 provided historical and future climatic data for the study area. An embankment was numerically modeled to evaluate the effect on slope stability due to the precipitation change induced by climate change. Coupled hydro-mechanical finite element analyses used a two-dimensional transient unsaturated seepage model and a limit equilibrium slope stability model. The study found that extreme climatic interactions like precipitation and temperature due to climate change may reduce embankment slope safety. The reduction in the stability of the embankment due to increased precipitation resulting from different greenhouse gas emission scenarios was investigated. The use of unsaturated soil strength and variation of permeability with suction, along with the phase transition of these earthen embankments from near-dry to near-saturated, shows how unsaturated soil mechanics and the hydro-mechanical model can identify climate change issues on critical geotechnical infrastructure. [ABSTRACT FROM AUTHOR]

In the present article, we report the magnetic, dielectric, and structural properties of the perovskite Bi0.5La0.5Fe0.4Al0.1Mn0.5O3. The structural analysis shows that this system crystallizes in a disordered orthorhombic phase with the space group Pnma. We found two consecutive magnetic transitions at 42 K and 147 K which have been suggested to be associated with the spin-glass and long-range ordering transitions, respectively. Further, temperature-dependent Raman spectra shows that this system has a spin-phonon coupling. Moreover, the dielectric measurement suggests that this system has a large dielectric constant at ambient temperature. Additionally, the dielectric spectrum suggests an unusual frequency-dependent step-like trend and the presence of weak relaxor ferroelectricity in the system. Thus, the presence of such multiple interesting characteristics suggests that Bi0.5La0.5Fe0.4Al0.1Mn0.5O3 can be used as spintronic devices and high dielectric applications. [ABSTRACT FROM AUTHOR]

Improvement in thermoelectric parameters is reported with graphite incorporation in n-type Bi2Te3/graphite nanocomposite systems. In-depth thermoelectric properties of nanostructured Bi2Te3/graphite composites are probed both microscopically and macroscopically using x-ray diffraction, Raman spectroscopy, inelastic neutron scattering, and measurement of the temperature dependence of thermal conductivity κ, Seebeck coefficient S, resistivity ρ, and carrier concentration nH. Raman spectroscopic analysis confirms that graphite introduces defects and disorder in the system. Graphite addition induces a large (∼17%) decrease of κ, originating from a strong phonon scattering effect. A low lattice thermal conductivity, κL, value of 0.77 W m−1 K−1, approaching the κmin value, estimated using the Cahill–Pohl model, is reported for Bi2Te3 + 1.0 wt. % graphite sample. Graphite dispersion alters the low-energy inelastic neutron scattering spectrum providing evidence for modification of the Bi2Te3 phonon density of states. Improvement in other thermoelectric parameters, viz., Seebeck coefficient and resistivity, is also reported. Theoretical modeling of electrical and thermal transport parameters is carried out and a plausible explanation of the underlying transport mechanism is provided assuming a simple model of ballistic electron transport in 1D contact channels with two different energies. [ABSTRACT FROM AUTHOR]

Current soil stabilization methods are often limited by durability and leaching issues and do not always offer sustainable treatments. This research explores the use of geopolymers to stabilize clays in the North Texas area. In recent years, geopolymer has received much attention as an eco-friendly and sustainable alternative to conventional chemical additives, since it can be processed at room temperature from aqueous solutions by utilizing waste materials and/or abounded natural sources. Two subgrade soils from North Texas were treated with GP mix at a ratio of 8 wt% dry GP to dry soil. GP is shown to reduce swelling and shrinkage potential of soil considerably while an increase in unconfined compressive strength is observed as well. Therefore, further studies are recommended to understand the mechanism of GP and soil bonding resulting in said changes.