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This paper presents the design of a strain-sensitive, dual ball-shaped tunable zone (DBT) taper structure for light intensity modulation. Unlike conventional tapered optical fibers, the DBT incorporates a central light field modulation zone within the taper. By precisely controlling the fusion parameters between single-mode fiber (SMF) and polarization-maintaining fiber (PMF), the ellipticity of the modulation zone can be finely adjusted, thereby optimizing spectral characteristics. Theoretical analysis based on polarization mode interference (PMI) coupling confirms that the DBT structure achieves a more uniform spectral response. In cantilever beam strain tests, the DBT exhibits high sensitivity and a highly linear intensity–strain response (R² = 0.99), with orthogonal linear polarization mode interference yielding sensitivities of 0.049 dB/με and 0.023 dB/με over the 0–244.33 με strain range. Leveraging the DBT’s light intensity sensitivity, a temperature-compensated intensity difference and ratio calculation method is proposed, effectively minimizing the influence of light source fluctuations on sensor performance and enabling high-precision strain measurements with errors as low as ±6 με under minor temperature variations. The DBT fiber device, combined with this innovative demodulation technique, is particularly suitable for precision optical sensing applications. The DBT structure, combined with the novel demodulation method, is particularly well-suited for high-precision and stable measurements in industrial monitoring, aerospace, civil engineering, and precision instruments for micro-deformation sensing.

Mn compounds presenting magneto-structural phase transitions are currently intensively studied for their giant magnetocaloric effect; nevertheless, several parameters remain to be further optimized. Here, we explore the Mn(Fe,Ni)(Si,Al) series, which presents two advantages. The Mn content is fixed to unity ensuring a large saturation magnetization, and it is based on non-critical Si and Al elements instead of the more commonly employed Ge. Structural and magnetic properties of MnFe0.6Ni0.4Si1-xAlx compounds are investigated using powder X-ray diffraction, SEM, EDX, DSC, and magnetic measurements. We demonstrate that a magneto-structural coupling leading to transformation from ferromagnetic with orthorhombic TiNiSi-type structure to a paramagnetic hexagonal Ni2In-type phase can be realized for 0.06 < x ≤ 0.08. Unfortunately, the first-order transition is relatively broad and incomplete, likely as the result of insufficient sample homogeneity. A comparison between samples synthesized in different conditions (as-cast, quenched from 900 °C, or quenched from 1100 °C) reveals that Mn(Fe,Ni)(Si,Al) samples decompose into a Mn5Si3-type phase at intermediate temperatures, preventing the synthesis of high-quality samples by conventional methods such as arc-melting followed by solid-state reaction. By identifying promising MnFe0.6Ni0.4Si1-xAlx compositions, this study paves the way toward the realization of a giant magnetocaloric effect in these compounds using alternative synthesis techniques.

Promethazine and scopolamine are two major components of a drug commonly used as a substitute for heroin addiction but with its own potential for abuse. Here, surface-enhanced Raman spectroscopy experiments were combined with density functional theory computations of the Raman frequencies of promethazine. The enhancement of the SERS substrate was optimized by contrast detection of silver nanoparticles. The optimized substrate was used to detect scopolamine, promethazine and their mixtures. Several mixtures of different concentrations were detected and analyzed. The approach of rapid identification and monitoring of drugs will become an important tool in the detection and control of illicit drug use.

LaCrO 3 (LCO) has promising applications as a p-type conductive material in the fields of transparent conducting oxes, high-temperature sensors, and magnetohydrodynamic power generators. However, the easy volatility of the Cr element, along with the issues of low electrical conductivity caused by the small-polaron conduction mechanism and wide band gap, has hindered the widespread application of LCO. In this work, based on band engineering and defect engineering, we screened doping schemes through first-principles calculations that can reduce Cr volatility by enhancing the Cr-O bond energy. We also aimed to promote small-polaron hopping and improve the electrical conductivity by introducing impurity levels. Additionally, we conducted a thorough analysis of the small-polaron conductivity mechanism. Through the solid-state method, we successfully prepared codoped LCO with Ca and Zn. The Zn dopants effectively enhanced the Cr-O bond strength, suppressed the Cr volatility, and improved high-temperature stability. The Zn dopants introduced additional impurity energy levels within the band gap, significantly changing the mobility of small polarons. Through optimal doping concentration, the La 0.7 Ca 0.3 Cr 0.95 Zn 0.05 O 3 sample demonstrated a significant enhancement in electrical conductivity compared to La 0.7 Ca 0.3 CrO 3 , increasing from 7 to 60 at 1000 K. Additionally, the impurity energy levels enhanced the asymmetry near the Fermi level, resulting in an increased Seebeck coefficient ( S ). This is beneficial for the production of high-temperature sensors. The output voltage of an LCO thermocouple module reaches up to 58 mV at 2170 K, indicating that the performance optimization strategy employed in this work has significant implications for the regulation and application of oxide electrical materials.

Critical phenomena are one of the most captivating areas of modern physics, whereas the relevant experimental and theoretical studies are still very challenging. Particularly, the underlying mechanism behind the anomalous thermoelectric properties during critical phase transitions remains elusive, i.e., the current theoretical models for critical electrical transports are either qualitative or solely focused on a specific transport parameter. Herein, we develop a quantitative theory to model the electrical transports during critical phase transitions by incorporating both the band broadening effect and carrier-soft TO phonon interactions. It is found that the band-broadening effect contributes an additional term to Seebeck coefficient, while the carrier-soft TO phonon interactions greatly affects both electrical resistivity and Seebeck coefficient. The universality and validity of our model are well confirmed by experimental data. Furthermore, the features of critical phase transitions are effectively tuned. For example, alloying S in Cu 2 Se can reduce the phase transition temperature but increase the phase transition parameter b. The maximum thermoelectric figure of merit zT is pushed to a high value of 1.3 at the critical point (377 K), which is at least twice as large as those of normal static phases. This work not only provides a clear picture of the critical electrical transports but also presents new guidelines for future studies in this exciting area., (© 2024. The Author(s).)

Silver sulfide in monoclinic phase (α-Ag2S) has attracted significant attention owing to its metal-like ductility and promising thermoelectric properties near room temperature. However, first-principles studies on this material by density functional theory calculations have been challenging as both the symmetry and atomic structure of α-Ag2S predicted from such calculations are inconsistent with experimental findings. Here, we propose that a dynamical approach is imperative for correctly describing the structure of α-Ag2S. The approach is based on a combination of ab initio molecular dynamics simulation and deliberately chosen density functional considering both proper treatment of the van der Waals interaction and on-site Coulomb interaction. The obtained lattice parameters and atomic site occupations of α-Ag2S are in good agreement with experimental data. A stable phonon spectrum at room temperature can be obtained from this structure, which also yields a bandgap in accord with experimental measurements. The dynamical approach thus paves the way for studying this important ductile semiconductor in not only thermoelectric but also optoelectronic applications., (© 2023 Author(s). Published under an exclusive license by AIP Publishing.)

Black phosphorus (BP) has been demonstrated as a promising electrode material for supercapacitors. Currently, the main limitation of its practical application is the low electrical conductivity and poor structure stability. Hence, BP-based supercapacitors usually severely suffer from low capacitance and poor cycling stability. Herein, a chemically bridged BP/conductive g-C 3 N 4 (BP/c-C 3 N 4 ) hybrid is developed via a facile ball-milling method. Covalent P-C bonds are generated through the ball-milling process, effectively preventing the structural distortion of BP induced by ion transport and diffusion. In addition, the overall electrical conductivity is significantly enhanced owing to the sufficient coupling between BP and highly conductive c-C 3 N 4 . Moreover, the imbalanced charge distribution around the C atom can induce the generation of a local electric field, facilitating the charge transfer behavior of the electrode material. As a result, the BP/c-C 3 N 4 -20:1 flexible supercapacitor (FSC) exhibits an outstanding volumetric capacitance of 42.1 F/cm 3 at 0.005 V/s, a high energy density of 5.85 mW h/cm 3 , and a maximum power density of 15.4 W/cm 3 . More importantly, the device delivers excellent cycling stability with no capacitive loss after 30,000 cycles.