A detailed investigation of the structural, electronic, vibrational, and dielectric properties of polycrystalline LaV0.5Nb0.5O4 samples, prepared at two sintering temperatures (1000 degrees C and 1250 degrees C) is presented. The introduction of Nb5+ at the V5+ site leads to notable structural and vibrational changes, which can be attributed to their isoelectronic nature and the comparatively larger ionic radius of Nb5+. The Rietveld refinement of the X-ray diffraction patterns confirms a coexistence of monoclinic (P2(1)/n) and scheelite-type tetragonal (I4(1)/a) phases; for example, with a fraction of 4 % and 96 % for the sample annealed at 1250 degrees C. The particle morphology has altered from spherical (1000 degrees C to irregular-shaped (1250 degrees C) as a result of increase in annealing temperature. The Raman spectroscopy, Fourier Transform Infrared spectroscopy and X-ray Photoemission Spectroscopy have been used to understand the vibrational and electronic properties. An optical band gap of 2.7 eV for the sample sintered at 1250 degrees C is calculated using Ultraviolet-vis diffuse reflectance spectroscopy measurements. The dielectric studies shows the higher dielectric permittivity (epsilon(r)) and lower dielectric loss for the sample annealed at 1250 degrees C.

We present the detailed study of the temperature dependent dielectric properties, impedance spectroscopy and electrical conductivity of LaV1−xNbxO4 (x=0–1) samples prepared by the solid-state reaction method. The dielectric constant (ϵr′) increases (decreases) with increase in the temperature (frequency); while, the magnitude of ϵr′ remains almost invariant (order of 104 at 100 Hz and 600 °C) with x. The single phase x=0 (monoclinic-monazite, P21/n) and x=1 (monoclinic fergusonite, I2/a) samples show the lower values of loss factor [tanδ= (4–8)] as compared to the x=0–0.8 samples [tanδ= (12–18)] having mixed tetragonal and monoclinic phases, which indicates the strong correlation between the crystal structure and the dielectric properties. The real part of impedance (Z′) decreases with both temperature and frequency, and the observed weak relaxation remains almost unaltered with x. The imaginary part of impedance (Z′′) shows strong relaxation peaks shifting towards higher temperatures with frequency, which is attributed to the effect of grains, grain boundaries, and electrodes in the samples. The activation energy of the relaxation process is estimated to be 0.8–1.0 eV for the x=0–0.6 samples, and ≈1.4 eV for the x=0.8; whereas the x=1 sample shows two values (≈0.5 eV and ≈1.0 eV) in the higher and lower temperature range, respectively. Further, the change in total conductivity with the angular frequency, which found to be in the range of 10−3 to 10−5 S/m, is fitted using the Jonsher power law. The analysis suggests the overlapping large polaron tunneling (OLPT) model for all the samples, whereas the x = 1 sample exhibit a transition near 480 °C and at higher temperatures it shows non-overlapping small polaron tunneling (NSPT) and quantum mechanical tunneling (QMT). This transition is corroborated by the tangent loss curves and may be associated with the change in structure.

The sintering behavior and functional properties of Ba0.95Bi0.02Ca0.02Zr0.02Ti0.976Cu0.008O3 (Abb. as BCZTCB) lead-free ceramics have been studied through appropriate techniques. The XRD technique reveals a perovskite phase with a pure tetragonal symmetry for samples sintered at 1260 degrees C & 1300 degrees C. However, it is observed to be an admixture of Tetragonal and Orthorhombic phases for samples sintered beyond 1300 degrees C. Microstructural evaluation evidences numerous pores for samples sintered at 1260 degrees C, while the microstructure appears very dense with fewer pores for sintering at 1340 degrees C. The co-doping of Cu2+/Bi3+ results in a significant reduction in sintering temperature along with an enhanced Curie temperature (TC) and improved temperature stability. The enhanced electrical properties obtained for sample sintered at 1340 degrees C are as follows: TC - 153 degrees C, & epsilon;max - 3276, tan & delta; - 2%, the degree of diffuseness (& gamma;) - 1.44, Remnant Polarization (Pr) = 10.8 & mu;C/cm2, Corrosive field (EC) = 11.2 kV/cm, and piezoelectric coefficient (d33) - 114 pC/N.

Lead-free 0.98(K0.5Na0.5)(Nb0.96Sb0.04O3)–0.02(Bi0.5Na0.5)(Zr0.8Sn0.1Hf0.1)O3 (0.98KNNS–0.02BNZSH) perovskite ferroelectric ceramics have been designed and prepared through the traditional ceramic fabrication technique. To have an insight on the effects of sintering temperature (in the range from 1020 to 1110 °C), the structural, microstructural, dielectric and ferro/piezoelectric properties of 0.98KNNS–0.02BNZSH ceramics are investigated systematically. The structural analysis has revealed a pure perovskite phase for sintering at different temperatures. The rhombohedral (R) and orthorhombic (O) phases coexist for sintering of 0.98KNNS–0.02BNZSH ceramic at 1080 °C, while the rhombohedral phase dominates above 1080 °C. The grains become more uniform and tightly packed when the sintering temperature is increased from 1020 to 1080 °C. However, the grain size and the density have been revealed to be decreased for samples sintered above 1080 °C. The conduction behavior of 0.98KNNS–0.02BNZSH ceramics has also been investigated using complex impedance spectroscopy. The optimum values of different dielectric and ferro/piezoelectric parameters for 0.98KNNS–0.02BNZSH ceramics sintered at 1080 °C are obtained to be as the following: TC ~ 317 °C, εmax ~ 7102, tanδ ~ 0.10, ρ ~ 4.49 g/cm3, d33 ~ 180 pC/N, and Pr ~ 16.7 µC/cm2. These findings show that crystallizability, density, and electrical properties are significantly influenced by the sintering temperature.

We investigate the structural, vibrational, morphological, and electronic properties of Nb substituted orthova-nadate LaV1-xNbxO4 samples prepared by the solid-state reaction method. The x-ray diffraction (XRD) analysis reveals the presence of three crystal structures [monoclinic monazite (m -m) type for the x = 0, two-phase equilibrium of monoclinic monazite (m -m) and tetragonal scheelite (t -s) type for the 0.2 = x = 0.8, and monoclinic fergusonite (m -f) type for the x = 1 samples] with an increase in Nb5+ concentration. The Raman spectroscopy and x-ray photoelectron spectroscopy (XPS) were employed to study the vibrational and electronic properties of all the samples, respectively. In order to choose an excitation wavelength that does not cause undesirable fluorescence and has observable intensities of all the vibrational modes, the Raman spectra are collected using 532 nm, 633 nm, and 785 nm laser lines. With increasing the Nb5+ concentration, new Raman modes associated with Nb-bonds are clearly visible and the intensity of V-bonds assigned modes is decreasing. The XPS analysis shows the unchanged 3+ oxidation state of La ion where the intensity of the V 2p core-level decreases while the Nb 3d core-level increases with x. The equal spin-orbit energy splitting of the states is confirmed by the average energy difference (across La core-level spectra for all the samples) for state I as well as bonding and anti-bonding of state II. Interesting, the relative intensity of La 3d state I and state II show systematic change with Nb doping altering the metal ligand overlap. We discuss and provide insight into the evolution of the structural, morphological, and chemical features with Nb substitution in LaV1-xNbxO4 samples.

Series of Al3+ doped Gd1.92Ti2-xO7:Eu0.08Al3+x (where x = 0, 0.02, 0.04, 0.06, & 0.08), powdered samples had been successfully developed using the solid-state reaction strategy. The purity of the produced samples was confirmed using X-ray diffraction analysis, while through Raman spectroscopy analysis and deconvolution, it has been observed that high intensity vibrational bands exhibited a blue shift (from 312.3 to 313.9 cm-1 and 518.2-518.6 cm-1) upon the introduction of Al3+ substitution in the Gd1.92Eu0.08Ti2O7 host lattice. Photoluminescence excitation spectra showed absorption in the ultraviolet & near-ultraviolet regions for Gd1.92Eu0.08Ti2O7, monitored at a wavelength of 588 nm. On the other hand, the Al3+ doped Gd1.92Eu0.08Ti2O7 oxides exhibited distinct absorption bands in 250-500 wavelength region, in addition to the host excitation bands. Under 322 nm excitation, the Al3+ doped Gd1.92Eu0.08Ti2O7 pyrochlore oxides displayed a dominant orange-reddish emission spike at 588 nm occurring due to 5D0 -> 7F1 transition, along with weak emission peaks at 612 nm originating from 5D0 -> 7F2 transition of trivalent europium ions. Similarly, under 394 nm excitation, the whole series exhibited analogous emission spikes, with the highly intense peak centered at 588 nm and weak band at 612 nm but in this case the emission intensity for all the peaks are relatively low as compared to when excited to 322 nm. The energy transfer processes and their relative possible reasons for concentration quenching above a Al3+ ion concentration of 2.0 mol% were discussed in detail. The optimized sample showed CIE chromaticity coordinates of (0.605, 0.392) under 322 nm excitation, indicating its positioning in the orange-reddish region. The CIE coordinates measured, depends on the emission profile under 322 nm excitation closely matched those of the economic phosphor Y2O2S:Eu3+ (x = 0.622 and y = 0.351). Overall, these results highlight the potential of Al3+ doped Gd1.92Eu0.08Ti2O7 pyrochlore oxides as orange-reddish emitting components for luminescent devices.

After the redefinition of the International System of Units (SI), it has been realized that the pascal, the SI unit of pressure, can be calculated more accurately because, according to ideal gas law, the pressure depends on temperature, gas number density, and few fundamental constants like Boltzmann’s constant, the universal gas constant, and Avogadro’s number. Among those, the temperature is redefined by evaluating the thermal energy. The fundamental constants are already calculated using quantum electrodynamics (QED) with the utmost accuracy. Therefore, the precise measurement of pascal depends majorly on gas number density, which can be computed using optical techniques. Quantum calculations involve calculating pressure using optical methods, also known as the quantum realization of pascal. This chapter reviewed the optical techniques for measuring pressure using refractometry proposed by various national metrology institutes.

We investigate the structural, vibrational, morphological, and electronic properties of Nb substituted orthovanadate LaV_1-xNb_xO_4 samples prepared by the solid-state reaction method. The x-ray diffraction (XRD) analysis reveals the presence of three crystal structures [monoclinic monazite (m-m) type for the x= 0, two-phase equilibrium of monoclinic monazite (m-m) and tetragonal scheelite (t-s) type for the 0.2≤x≤0.8, and monoclinic fergusonite (m-f) type for the x= 1 samples] with an increase in Nb^5+ concentration. The Raman spectroscopy and x-ray photoelectron spectroscopy (XPS) were employed to study the vibrational and electronic properties of all the samples, respectively. In order to choose an excitation wavelength that does not cause undesirable fluorescence and has observable intensities of all the vibrational modes, the Raman spectra are collected using 532 nm, 633 nm, and 785 nm laser lines. With increasing the Nb^5+ concentration, new Raman modes associated with Nb-bonds are clearly visible and the intensity of V-bonds assigned modes is decreasing. The XPS analysis shows the unchanged 3+ oxidation state of La ion where the intensity of the V 2p core-level decreases while the Nb 3d core-level increases with x. The equal spin-orbit energy splitting of the states is confirmed by the average energy difference (across La core-level spectra for all the samples) for state I as well as bonding and anti-bonding of state II. Interesting, the relative intensity of La 3d state I and state II show systematic change with Nb doping altering the metal ligand overlap. We discuss and provide insight into the evolution of the structural, morphological, and chemical features with Nb substitution in LaV_1-xNb_xO_4 samples.

Abstract 0.9Bi1- x Nd x FeO3 − 0.1PbTiO3 solid solution with x = 0.05, 0.10, 0.15 and 0.20 were success fully synthesized by the standard solid-state reaction method. The effect of Nd3+ion substitution on structural, micro structural, ferroelectric, magnetic and dielectric properties of 0.9BiFeO3-0.1PbTiO3 have been investigated. The XRD analysis for the samples under study revealed distorted rhombohedral structure with R3C space group. 0.9Bi1- x Nd x FeO3 − 0.1PbTiO3 i.e. (BNFPT)x with x = 0.05, 0.10, 0.15 and 0.20 compounds crystallized as single-phase materials with the same structure as the parent BiFeO3 compound. The SEM study revealed the uniform grain scattering for all prepared samples. Raman spectroscopy showed disappearance of some Raman modes indicated a structural phase transition with substitution of Nd dopants at Bi site and also confirmed the distorted rhombohedral perovskite structure of (BNFPT)x compounds with R3c symmetry. Dielectric measurements reveals that, around Neel temperature, all the samples exhibit magneto-electric coupling and also improved dielectric properties with addition of dopants in BiFeO3(BFO) compound. All the prepared samples exhibit weak ferro-magnetic character at room temperature. However, the variation in linear behavior and enhancement in magnetization is found at 5 K which shows gradual increase in remnant magnetization from 0.00785 emu/g to 0.37513 emu/g with increase in Nd doping for all (BNFPT)x samples. Nd doping reduces leakage current by three orders of magnitude, from 10−4 to 10−7. Ferroelectric study revealed the pinning effect in hysteresis loops with low remnant polarization and coercive field which can be related to the energy storage performance of the samples.

In this work, Bi3+ doped Ba0.98- 3x/2BixCa0.02Zr0.02Ti0.976Cu0.008O3 [0 <= x <= 0.03] lead free ceramics, to be employed for structural, dielectric and ferroelectric studies, have been synthesized via conventional solid state reaction method. Rietveld refinement of the X-ray diffraction (XRD) data evidences the existence of a pure perovskite phase with tetragonal symmetry for all ceramics. The Scanning Electron Microscopy (SEM) reveals that the grain size, which is 16.14 mu m for x = 0 reduced to 2.11 mu m for x = 0.03. Dielectric studies demonstrate excellent dielectric behavior with high Curie temperature (T-C similar to 159 degrees C), high dielectric constant (epsilon(r) similar to 834, epsilon(max) similar to 3146), and a low dielectric loss (tan delta similar to 0.019), for an optimum value of x = 0.02. The analysis of temperature coefficient of the dielectric permittivity indicates the applicability of these materials in multilayer ceramic capacitors. Impedance studies, conducted to understand the underlying physical mechanisms, are found to be in good agreement with the results of structural and dielectric studies. Furthermore, the ferroelectric measurement confirms the ferroelectric nature for all samples with an energy storage efficiency (eta) of similar to 42% for x = 0.02 composition.

In the present work, lead-free piezoelectric ceramics (Rx)(K0.5Na0.5)(Nb0.96Sb0.04O3)−x(Bi0.5Na0.5)(Zr0.8Sn0.1Hf0.1)O3 [abb. as (Rx)KNNS−xBNZSH, 0 ≤ x ≤ 0.04] were prepared via solid-state sintering technique. The thermal behavior of mixed powders has been investigated for x = 0, 0.02, and 0.04 using TGA-DSC analysis to estimate the calcination temperature. The structural, morphological, dielectric, ferroelectric and piezoelectric properties are analyzed through the appropriate characterization techniques. The X-ray diffraction (XRD) patterns demonstrate a pure perovskite phase structure for all the sintered samples. Further, the coexistence of rhombohedral to orthorhombic (R-O) phase is observed in ceramic sample with x = 0.02. The morphology of all the sintered samples exhibits an inhomogeneous, dense microstructure with the rectangular grain, while for x = 0.02, a relatively homogeneous distribution of grains is observed. BNZSH doping decreases the average grain size from 2.22 to 0.33 μm for x = 0 to x = 0.04, respectively. Owing to the presence of multiple-phase coexistence as well as the improved microstructure and enhanced dielectric properties (dielectric constant εr = 1080, εmax = 5301; Curie temperature - TC ~ 317 °C; dielectric loss - tanδ ~ 6%) the ceramics with x = 0.02 has been found to have a large piezoelectric coefficient (d33) of ~180 pC/N, remnant polarization (Pr) ~ 16.7 µC/cm2 and coercive field (Ec) ~ 10.7 kV/cm. We believe it will expand the range of applications for KNN-based ceramics.

In this study, a comparison of structural changes on hydrogen loading-deloading cycles in palladium (Pd) nanoparticle layer and Pd thin film has been carried out. Cracks start to appear in the Pd thin film, which grow in size on continuous hydrogen loading-deloading cycles while no such phenomenon is observed in the nanoparticle layer. The XRD studies of the samples suggest that stress is generated in thin films on hydrogenation, which, when released, results in the crack formation. In comparison, due to low interaction with the substrate, nanoparticles are free to expand in all the directions and hence no stress is generated in the nanoparticle layer on being subjected to hydrogen loading deloading cycles. The variation in the XPS core level peak positions, before and after hydrogenation cycles support the inferences drawn from the XRD and SEM analysis of the samples.

In the present work, the effect of size, pressure and carbon shell thickness on the hydrogen induced structural modifications in Pd-C core-shell nanoparticles (NPs) have been inves-tigated by in-situ X-ray diffraction (XRD) technique. XRD study shows contraction in the lattice with decrease in size of the NPs. Hydrogen pressure dependent alpha-to beta-phase tran-sition is observed on increasing hydrogen pressure (1 x 10(-4) to 100 mbar). Compared to pure Pd NPs, occurrence of alpha <-> beta phase transition at lower H pressure in Pd-C NPs in-dicates that Pd-H interaction is enhanced by the carbon shell. Further, increasing hydrogen partial pressure is accompanied by an increase in the lattice parameter along with the formation of b-phase. Change in lattice constant (Da) at different rates indicates the relative dominance between adsorption and desorption at different pressures. The merits of Pd-C core shell NPs over bulk analogues make it a promising material for repeated hydrogen cycling applications. (c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

The paper describes the design, development, and characterization of a low profile, lightweight and linearly polarized fan beam radiating array antenna for millimeter wave fencing system.Dual antenna topology has been proposed for each transmit and receive tower to obtain maximum coverage area compared to a single antenna configuration.The radiator placement (height) has been optimized to minimize the dead zone region.Proposed RF fencing system utilizes an 8x32 probe-fed microstrip patch array antenna developed on 10 mils RT Duroid dielectric substrate material.ANSYS's High-Frequency Structure Simulator (HFSS) full-wave EM software has been utilized for simulation and analysis of designed radiating array.VSWR of the realized antenna is 1.75:1 over the frequency band of 34.5 GHz to 35.5 GHz.The E-plane and H-plane HPBW of the developed antenna at 35 GHz is 8.4 and 2.2 degrees respectively.The measured gain of the antenna is better than 25.4dBi over the frequency band 34.5 GHz to 35.5 GHz.