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This study examines the effects of varying calcination temperatures on the properties of Ni0.4Cu0.4Cd0.2Fe2O4 spinel ferrites. As confirmed by X-ray diffraction measurements, the compound calcined at 950°C exhibits a larger average crystallite size and lattice constant than the sample calcined at 850°C. The electrical conductivity study demonstrated semiconductor behavior for both samples, following the non-overlapping small polaron tunneling (NSPT) model for conduction. The samples showed high electrical resistivity and decreased activation energy (Ea) from 0.33 eV (at 850°C) to 0.31 eV (at 950°C), suggesting that they could be used in microwave absorption devices. The optical measurements reveal that the samples present direct optical transitions with an estimated optical bandgap energy (Eg) of 2.61 eV at 850°C and 2.39 eV at 950°C. Analyzing the refractive index change provided the Cauchy parameters, while the Wemple–DiDomenico relationship provided the dispersion energy parameters. Other optical characteristics, like the extinction coefficient, penetration depth, dielectric constants, and optical conductivity, were also thoroughly examined. These optical characteristics offered insightful information about the synthesized samples' possible optoelectronic uses. [ABSTRACT FROM AUTHOR]

In the present study, the hydrogen-absorption properties of the LaNi5 and the La0.7Ce0.1Ga0.3Ni5 compounds were determined and compared. This work is therefore divided into two parts: an experimental part that presents and discusses the kinetics and isotherms of hydrogen absorption in the two compounds at two different temperatures (298 K and 318 K). In addition, the temperature variations inside the hydride bed were determined. In the second section, the experimental isotherms were compared to a numerical model processed using statistical physics. Following that, thanks to the perfect agreement between the experimental data and the proposed model, the stereographic and energetic parameters associated with the hydrogen absorption reaction, such as the number of hydrogen atoms per receptor site (n1, n2), the densities of the sites (Nm1, Nm2), the half-saturation pressures (P1, P2) and the absorption energies (ΔE1, ΔE2) for each receptor site, were calculated. All of these parameters are acquired by making numerical adjustments to the experimental data. Thermodynamic functions, such as internal energy and Gibbs energy, which regulate the absorption process, were then identified using these parameters. For both compounds, all of the aforementioned were compared and discussed in relation to initial temperature and pressure. The results demonstrated that the hydrogen-storage properties in LaNi5 are enhanced by more than 30% of stored mass and kinetics when Ce and Ga are substituted at the La sites. [ABSTRACT FROM AUTHOR]

The results of an experimental and mathematical study into the MmNi4.2Mn0.8 compound's hydrogen storage properties are presented in the present research. Plotting and discussion of the experimental isotherms (P-C-T) for different starting temperatures (288 K, 298 K, 308 K, and 318 K) were carried out first. Then, the enthalpy and entropy of formation (ΔH0, ΔS0) were deduced from the plot of van't Hoff. Following that, the P-C-T were contrasted with a mathematical model developed via statistical physics modeling. The steric and energetic parameters, such as the number of the receiving sites (n1, n2), their densities (Nm1, Nm2), and the energy parameters (P1, P2) of the system, were calculated thanks to the excellent agreement between the numerical and experimental results. Therefore, plotting and discussing these parameters in relation to temperature preceded their application in determining the amount of hydrogen in each type of site per unit of metal ([H/M]1, [H/M]2) as well as for the entire system [H/M] versus temperature and pressure besides the absorption energies associated with each kind of site (ΔE1, ΔE2) and the thermodynamic functions (free energy, Gibbs energy, and entropy) that control the absorption reaction. [ABSTRACT FROM AUTHOR]

The effect of Nb for Ti substitution on the electrical, modulus, dielectric and conductivity behaviors of a ceramic perovskite, barium lanthanum titanate (BLTi1-xNb4x/5), Ba0.97La0.02Ti1-xNb4x/5O3, for x = 0.07 and 0.10, was investigated at a 0 V d.c. bias potential. The flux reaction method was used to create our solid solutions. With a rising niobium amount, electrical conductivity rose. Jonscher's universal power law was used to fit the experimental results. The fact that the exponent n is marginally greater than 1 suggests that the hopping takes place between neighboring sites. As frequency rose, the dielectric constant dropped. Maxwell–Wagner (M-W) interface polarization is responsible for this behavior. Complex impedance spectroscopy was used to inspect the electrical characteristics in the frequency band (100–106 Hz), at a 0 V d.c. bias potential. With increasing Nb concentration, the real and imaginary components of impedance rose. Each sample was represented by a single impedance semicircle on the complex impedance plot that was visible over both high and low frequencies. The measurement of the complex electrical modulus spectrum revealed the impact of grain boundaries and grains on electrical properties. A mismatch between the two maxima of the impedance and electrical modulus normalization curves was observed, which points to the possibility of short-range motion of charge carriers. [ABSTRACT FROM AUTHOR]

Fe2O3 and SmFeO3 were synthesized using a sol–gel method based on Pechini's technique. At ambient temperature, an X-ray powder diffraction indicated that these compounds crystallize in the monoclinic system with Pnma, hexagonal system, and R-3c space group for Fe2O3 and SmFeO3, respectively. As a result, the current study looked into the shape and electrical properties of Fe2O3 and SmFeO3 samples. Moreover, scanning electron microscopy was used to show both substances' morphologies and average particle size. The complex impedance diagram displayed a single semicircle, showing that the response originates with the grains. Thus, an equivalent circuit has been presented to explain the impedance data. Jonscher's power law of frequency was used to study AC conductivity. Then, as a function of inverse temperature, the σdc variation supports the presence of two phases for both compounds, where a distinct conduction mechanism ensures conductivity. On the other hand, the dielectric investigation verifies the transformation of the Fe2O3 compound at T = 565 K and the start of the ferroelectric transition for the SmFeO3 compound. [ABSTRACT FROM AUTHOR]

Lead-free Ferroelectric Niobium-doped Ba0.97La0.02Ti(1−x)Nb4x/5O3 (for x = 0.07 and 0.1) (BLTi(1−x)Nb4x/5) system was synthesized by the powders MS-ceramic (Molten-Salt) method. These systems’ X-ray diffraction data underwent Rietveld analysis, which revealed that the samples formed in the pure tetragonal perovskite phase, at room temperature. The dielectric characteristics of ceramics with x = 0.07 and 0.1 were investigated across temperature (from 300 to 700 K) and frequency (from 1 Hz to 1000 kHz) range. In these ranges, it was discovered that the dielectric constant rose as the temperature and frequency rose. These characteristics have been clarified in terms of the prepared ceramic’s relaxation process using Debye, V–F (Vogel–Fulcher), and Power law relations. Through the use of parameter goodness, the appropriate model was predicted. The values are within an appropriate range and satisfactorily explain the aim of these prepared compounds have potent relaxation properties. [ABSTRACT FROM AUTHOR]

An investigation of the structural, morphological, magnetic, and optical properties of Ni0.6Mg0.2Co0.2FeCrO4 spinel ferrites prepared by the sol–gel method at different annealing temperatures conducted. The grain size and the unit cells parameters of the synthesized samples exhibit an increasing trend as the annealing temperature increases. A low coercive field was obtained from the hysteresis loops, making Ni0.6Mg0.2Co0.2FeCrO4 ferrites suitable candidates for soft magnetic devices. The bands associated with the tetrahedral (A) and octahedral [B] sites shift toward higher wavenumbers as the annealing temperature increases. In addition, the optical band gap energy decreases with annealing temperature due to the increase in grain size. From the absorbance and the Tauc method, the samples present direct optical transitions. Moreover, the determined Urbach energies are significantly low and decrease with annealing temperature. This implies that the degree of disorder and defects in the prepared samples decreases by increasing the annealing temperature. A detailed study has also been conducted on the variations versus wavelength of penetration depth, refractive index, extinction coefficient, dielectric constants, conductivity, and loss factor. From the variations of these optical parameters, some interesting optoelectronic applications were deduced for the prepared samples. [ABSTRACT FROM AUTHOR]

The structural, mechanical, electronic, and optical characteristics of Alkali chalcogenide and oxychalcogenides, i.e., A 2 O 2 B 2 Se 3 (A = Sr, Ba; B = Bi, Sb), were investigated using density functional theory (DFT). After full relaxation, the obtained structural parameters are in good agreement with the experimental parameters. Furthermore, the calculated elastic stiffness C i j shows that all of the studied compounds followed the mechanical stability criteria. Ductility for these compounds was analyzed by calculating Pugh's ratio; we classified the Sr 2 O 2 Bi 2 Se 3 , Sr 2 O 2 Sb 2 Se 3 , and Ba 2 O 2 Bi 2 Se 3 as ductile, and the Ba 2 O 2 Sb 2 Se 3 as brittle. The Debye temperature and acoustic velocity were estimated. In addition, electronic and chemical bonding properties were studied from the analysis of the band structure and density of state. The main features of the valence and conduction bands were analyzed from the partial density of states. Electronic band structures are mainly contributed to by Se- 4 p and Bi- 6 p /Sb- 5 p states. Direct band gaps are 0.90, 0.47, and 0.73 eV for Sr 2 O 2 Bi 2 Se 3 , Sr 2 O 2 Sb 2 Se 3 , and Ba 2 O 2 Sb 2 Se 3 , respectively. The Ba 2 O 2 Bi 2 Se 3 compound has an indirect band gap of 1.12 eV. Furthermore, we interpreted and quantified the optical properties, including the dielectric function, absorption coefficient, optical reflectivity, and refractive index. From the reflectivity spectra, we can state that these compounds will be useful for optical applications. [ABSTRACT FROM AUTHOR]

The use of solid-state electrolytes (SSEs) instead of liquid organic electrolytes presents one of the important means to increase the energy density and resolve the protection issues of lithium batteries. The development of SSEs compounds, which can suit high-voltage cathodes and lithium metal anode (LMA) is rather important to progress high-energy–density lithium batteries. Among the different compounds, lithium aluminum titanium phosphates (LATP) are especially potential candidates for all-solid-state batteries (ASSBs) since their present high ionic conductivity, superior air stability, and low cost. In this paper, the Li1+xAlxTi2−x(PO4)3 (LATP) compounds with different mixtures have been synthesized via solid-state technique. The rhombohedral phase (space group R 3 ¯ c ) of these samples is confirmed through the powder X-ray diffraction measurements. The thermogravimetric (TG) measurements show that when x-content increments in LATP, the integral temperature of decomposition reduces. Likewise, the temperature whereupon the samples turn stable decreases, which suggested that phase stability is related by the rise of the x-content in the basic sample. Through the 101–106 Hz frequency area, the real and imaginary parts of the dielectric permittivity, the electric modulus, and alternating current (AC) conductivity of LATP samples display temperature reliance. The different contributions of grains and grain boundaries to the total impedance are confirmed by the Nyquist curves. The alternating current (AC) conductivity is illustrated in terms of Jonncher's power law. The studies on charge transportation suggest the presence of the overlapping large polaron tunneling mechanism (LATP − x = 0.0) and the non-overlapping small polaron tunneling mechanism (LATP − x = 0.3 and LATP − x = 0.5). [ABSTRACT FROM AUTHOR]