Electrical transport properties of layered structure bismuth oxide: Ba0.5Sr0.5Bi2V2O9

The layered structure bismuth oxide, Ba_0.5Sr_0.5Bi₂V₂O₉, was prepared using solid state reaction technique. Room temperature X-ray diffraction study confirms the formation of the material with an orthorhombic crystal structure. The temperature dependent impedance parameters were investigated using an impedance analyzer in a wide range of frequencies (10²–10⁶ Hz) at different temperatures. The Nyquist plots reveal the presence of both grain and grain boundary effect above 275 °C. The bulk resistance of the material decreases with rise in temperature which shows negative temperature coefficient resistance behavior like semiconductor. The variation of ac electrical conductivity (σ_ac) was measured, and the activation energy of the material found to be 0.36, 0.33, 0.34, 0.31 eV at 10, 50, 100 and 500 kHz respectively. Ac conductivity data were used to evaluate the density of states at Fermi level. From the dynamic light scattering and electrophoretic light scattering study, it is observed that the particle show excellent aqueous dispersion stability without any change in hydrodynamic size and zeta potential.     

Structural refinement,optical and electrical properties of [Ba1−x Sm2x/3](Zr0.05Ti0.95)O3 ceramics

Samarium doped barium zirconate titanate ceramics with general formula [Ba_1?x Sm_2x/3](Zr_0.05Ti_0.95)O₃ [x = 0, 0.01, 0.02, and 0.03] were prepared by high energy ball milling method. X-ray diffraction patterns and micro-Raman spectroscopy confirmed that these ceramics have a single phase with a tetragonal structure. Rietveld refinement data were employed to model [BaO₁₂], [SmO₁₂], [ZrO₆], and [TiO₆] clusters in the lattice. Scanning electron microscopy shows a reduction in average grain size with the increase of Sm³⁺ ions into lattice. Temperature-dependent dielectric studies indicate a ferroelectric phase transition and the transition temperature decreases with an increase in Sm³⁺ ion content. The nature of the transition was investigated by the Curie–Weiss law and it is observed that the diffusivity increases with Sm³⁺ ion content. The ferroelectric hysteresis loop illustrates that the remnant polarization and coercive field increase with an increase in Sm³⁺ ions content. Optical properties of the ceramics were studied using ultraviolet–visible diffuse reflectance spectroscopy.     

Structural,dielectric and electrical properties of a new tungsten bronze ferroelectric ceramics

The polycrystalline sample of Li₂Pb₂Nd₂W₂Ti₄Ta₄O₃₀ was prepared by a solid-state reaction technique. Room temperature X-ray structural analysis confirms the formation of a single phase compound. The morphology of the sintered sample recorded by scanning electron microscope exhibits a uniform grain distribution. Detailed studies of the nature of variation of dielectric constant, tangent loss and polarization with temperature and frequency confirmed the existence of ferroelectricity in the material. The temperature and frequency dependence of impedance parameters (impedance, modulus, etc.) of the material exhibits a strong correlation of its micro-structure (i.e., bulk, grain boundary, etc.). The nature of variation of pyroelectric-coefficient and current with temperature suggests that material has good pyroelectric properties useful for pyroelectric detector.     

Structural and electrical properties of La-modified BiFeO3–BaTiO3 composites

In the present investigation, La-modified solid solutions of BiFeO₃ (BFO) and BaTiO₃ (BT) in different molar ratios [i.e., (Bi_0.5?x La _x Ba_0.5)(Fe_0.5Ti_0.5)O₃, with x = 0.0, 0.05, 0.10 and 0.15)] have been synthesized using a solid-state reaction route. Structural and electrical properties of single phase (with minor secondary phase) of BFO–BT system have been studied in details to understand their ferroelectric and other properties. Preliminary X-ray diffraction analysis confirms the formation of a new system, which is different from that of its parent compounds. Substitution of a small amount BaTiO₃ into BiFeO₃ enhances dielectric and ferroelectric responses and reduces electrical leakage or tangent loss. The ac conductivity obeys Jonscher’s universal power law. The electrical behavior of the samples was investigated by impedance spectroscopy in a wide temperature range (25–525 °C) at different frequency (1 kHz–1 MHz). The impedance spectroscopy of the materials also confirms the origin of the relaxation mechanism in the system.     

Sunflower Oil and Protein-based Novel Bigels as Matrices for Drug Delivery Applications—Characterization and in vitro Antimicrobial Efficiency

The current study deals with the characterization of sunflower oil- and protein-based bigels for drug delivery applications. Span-40 was used as an organogelator for the preparation of bigels. The bigels were characterized by microscopy, XRD, thermal, texture studies and impedance spectroscopy. The microscopic studies revealed that the droplets were apolar in nature (organogels), while the continuum phase was polar in nature (protein hydrogel matrix). Incorporation of the proteins improved the stability of the bigels. The release of the drugs followed diffusion kinetics. The bigels showed good antimicrobial efficiency against E.coli and were cytocompatible in presence of L929 cells.     

A chemically stable nanoporous coordination polymer with fixed and free Cu2+ ions for boosted C2H2/CO2 separation

Safely and highly selective acetylene(C₂H₂)capture is a great challenge,because of its highly explosive nature,as well as its nearly similar molecule size and boiling point toward the main impurity of carbon dioxide(CO₂).Adsorption separation has shown a promising future.Herein,a new nanoporous coordination polymer(PCP)adsorbent with fixed and free Cu ions(termed NTU-66-Cu)was prepared through post-synthetic approach via cation exchanging from the pristine NTU-66,an anionic framework with new 3,4,6-c topology and two kinds of cages.The NTU-66-Cu shows significantly improved C₂H₂/CO₂selectivity from 6 to 32(v/v:1/1)or 4 to 4₂(v/v:1/4)at low pressure under 298 K,along with enhanced C₂H₂capacity(from 89.22to 111.53 cm³·g^-1).More importantly,this observation was further validated by density functional theory(DFT)calculations and breakthrough experiments under continuous and dynamic conditions.Further,the excellent chemical stability enables this adsorbent to achieve recycle C₂H₂/CO₂separation without loss of C₂H₂capacity.     

Study of combined effect of natural convection and radiation heat transfer from annular finned vertical cylinder

The present numerical study reports the combined effect of natural convection and radiation heat from a vertical cylinder with annular fins. The study involves simulation for laminar as well as turbulent regimes. For the present study, Rayleigh's number is varied in the range ${10}^8-{10}^{12}$, emissivity in the range $0.2-0.8$, and the fin spacing ratio (s/d) in the range $0.1-10$. The radiation heat transfer has been found to share a considerable amount in the total heat transfer of the system for the laminar regime, but in the turbulent regime, its effect is minimal and can be neglected. When the fin spacing ratio is reduced, the total heat transfer increases for both the turbulent and laminar flow conditions. But the radiation heat increases with a reduction in fin spacing ratio for laminar and in case of turbulent flow radiation heat rate reduces with a reduction in s/d ratio. For the range of Rayleigh numbers considered in the present study, the Nusselt number increases with the increment of the fin spacing ratio. Thus, it can be concluded that there is a remarkable enhancement in the heat transfer rate in laminar cases with the fins. For turbulent cases, the fin efficiency lies between 40% and 50%.     

A Simulation Approach to Study the Effect of SiC Polytypism Factor on Sensitivity of Piezoresistive MEMS Pressure Sensor

Silicon - SiC is a well known wide band gap semiconductor explored for realizing the piezoresistive micro-electro-mechanical systems (MEMS) pressure sensors for harsh environments. In this work a...