Space Group Pm3m Research Articles

Investigation of the behaviour of tunable chalcogenide-Bismuth based perovskite BiTl (SxSe1-x)3(X = 0, 0.33, 0.67, 1): first principles calculations

Density functional theory (DFT) driven by the quantum ESPRESSO code was used in this study to investigate the structural, opto-electronic, and thermoelectric properties of ternary perovskite chalcogenide compound. This is to examine their possible use in optoelectronics and reducing the dependency on silicon and fossil fuel. The Perovskite compounds crystalize in the cubic phase with a space group Pm-3m. The volume versus energy is fitted by the Birch-Murnaghan equation of state which yielded the equilibrium lattice constant of 8.353, 8.488, 8.629 and 8.806, bulk modulus of 255.8, 242.7, 233.5 and 222.4, for BiTlS3 , BiTlS2 Se1 , BiTlS1 Se2 and BiTlSe3 . Indirect band gaps of 2.6 eV, 2.7 eV, 2.9 eV, and 3.2 eV were obtained for BiTlS3 , BiTlS2 Se1 , BiTlS1 Se2 and BiTlSe3 compounds, respectively. Also, increment in the energy from 0 eV to 10 eV resulted in optical properties fluctuation within 0 cm-1 to 1.5 × 109 cm-1 for absorption coefficient in the compounds. However, a variation from 10 eV to 20 eV moved the absorption coefficient to 4.2 × 109 cm-1 for all the compounds from visible to the UV range. Furthermore, the observed properties show that the value of figure of merit obtained is 0.125 for BiTlS3 , 0.100 for BiTlS2 Se1 , 0.068 for BiTlS1 Se2 and 0.055 for BiTlSe3 at 300 K. By adjusting the chalcogen ratio, BiTlX3 (X = S, Se) possess the tunable band gap in the whole visible light range, which is of great significance for the development of new-type, high-efficient semiconductor material and optoelectronic devices, while the low thermoelectric values predict the compounds use as sensors. The proposed results may pave the way for further investigations into the use of the perovskite compounds for optoelectronic devices.

Structural, Microstructural, Dielectric and Ac-conductivity of CaTi1-xFexO3 Multiferroic Materials Synthesized by Solid State Method

In this study, the structural, microstructural, dielectric and conductivity properties of Fe-doped CaTiO3 (CT) ceramic were investigated. These ceramics were successfully synthesized using the conventional solid-state method. The X-ray diffraction and Rietveld refinement results showed that the ceramics at x=0.0, 0.1, 0.2 and 0.3 crystalized in the orthorhombic phase with the Pmmm space group. While for x=0.4, 0.5 and 0.6, the phase formation changes from orthorhombic to tetragonal phase with P4/mmm group space. The SEM results revealed a semi-spherical shape of grain for lower Fe content (≤0.4), while at x=0.5 and 0.6 an agglomeration phenomenon is observed and the observed density of the sample at x=0.5 is higher than the other ceramics. The dielectric properties were studied as function of frequency and temperature. The dielectric permittivity (ɛ’r) decreases as function of frequency at lower frequency region and remain almost independent of frequency at high frequency region in the whole temperature range of R.T–520 °C. Each converges at high frequency (>105 Hz) for all the temperatures. The evolution of ɛ’r as function of temperature for pure CT ceramic showed a stability at large range of temperature (from R.T to 250°C). For substituted ceramics, we obtained a phase transition which shifted to the lower temperature with the increase of Fe content. And the value of ɛ’r, increases for Fe-doped CT ceramics and reaches a maximal value for x=0.5 which is 50 time bigger than the pure ceramic. The AC conductivity, σAC, is found to increase rapidly as a function of frequency, at low frequency region, and increases linearly at high frequency region, which confirms the hopping of electrons related to the conduction mechanism. The σAC evolution is found to follow the Jonscher’s law and the s exponent decreased with the increasing temperature which is related to the correlated barrier height (CBH) model. And the σAC values increase with the increases of Fe content.

Predictions on new Cu-based ABO3 (A=Cu and B=Lu, Y) oxide-perovskite for energy storage and optoelectronic applications: A DFT study

Cu-based novel oxide-perovskite ABO3(A = Cu and B=Lu, Y) compounds have been investigated for their physical properties using the Generalized Gradient Approximation and Revised-Perdew-Burke-Ernzerhof (GGA-RPBE) exchanging correlation-functional within the density functional theory (DFT). The calculations show that both compounds comprise a cubic structure with the space group of Pm3m. The calculations also indicate that the results we have discovered represent unique compounds. Formation enthalpy computations have been used to assess the overall structural stability of both compounds. The density of states and band structure graphs for both perovskite compounds provide strong evidence of their semiconducting behavior. In-depth research is also done on optical properties such as the refractive index, extinction coefficient, absorption, reflectivity, electrical conductivity, and the energy loss function. At high-energy photons, both compounds CuLuO3 and CuYO3 show outstanding conductivity and absorption. While, at lower incident photon energy intervals, they both exhibit transparency. Based on our electronic and optical properties investigations, we have found that CuLuO3 and CuYO3 are potential candidates for use in high-energy UV, and optoelectronic technologies.

Intermediate-spin state of Co ions in magnetic and thermoelectric properties of double perovskite Ba2CoNbO6

Double perovskite Ba2CoNbO6, obtained by pyrolysis of nitrate-organic mixtures, was studied by XRD, XRF, DFT, AC/DC-magnetization, specific-heat, thermoelectric, and ESR methods. The sample has cubic symmetry space group Pm3m with a = b = c = 4.0074(11) Å. Deficiency in oxygen ions shows the presence of Co ions in both 3+ and 2+ valency. According to AC-magnetization and specific-heat data, Ba2CoNbO6 demonstrates spin-glass ordering at TSG = 30 K at external field value of 0.1 kOe. This temperature of spin glass transition drops with field power increase down to complete suppression at 10 kOe. The effective magnetic moment determined using the Curie-Weiss approximation is 4.29 μB, which is consistent with the theoretical estimation for Co ions in the intermediate-spin state. The peak at T = 90 K, observed in the temperature dependence of the specific heat and accompanied by a peak in the ESR linewidth, is possibly due to the structural transition at this temperature. The Seebeck coefficient of the compound is S = 4–6.5 μV/K and the band gap obtained within the small-polaron-jump conductivity model is ΔE = 0.284 eV in the temperature range of 350–550 K connected with DFT calculation. An intensity ESR line, related to Co2+ ions, was observed in ESR spectra.

Structural and Electrochemical Characterisation of NBZFO Cobalt-Free Cathode Material for Intermediate-Temperature Solid Oxide Fuel Cells: An Experimental Investigation

Compared to other energy-generating technologies and energy conversion devices, intermediate-temperature solid oxide fuel cells (IT-SOFCs) have gained significant attention from energy experts due to its high energy density, moderate operating temperature (600–800°C), low emissions and reliability. Enhancing the performance of IT-SOFCs requires suitable and excellent cathode materials. Thus, a perovskite-type Nd0.5Ba0.5Zr0.8Fe0.2O3+δ (NBZFO) material was synthesised via traditional solid-state reaction technique and analysed as a potential cathode material for IT-SOFCs. Analysis of X-ray diffraction data (XRD) revealed a single-phase perovskite material that crystallises in cubic space group (pm-3m). The thermal and electrochemical properties were analysed with the aid of thermogravimetric analysis (TGA) and electrochemical impedance spectroscopy (EIS). NBZFO has an electrical conductivity in air of 80 S cm−1 at 400°C and a polarisation resistance (Rp) of 0.106 Ω cm2 at 800°C. TGA reveals a slight loss in weight of about 0.58%, thereby suggesting a highly stable cathode material for IT-SOFC. Electrochemical investigation shows that NBZFO has good electronic and ionic conductivity and excellent oxygen stichometry. Further studies are required to understand the effects of varying B-site composition of the cathode material.

Exploring the inorganic perovskite materials Mg3SbX3 (Where, X=I, Br, Cl and F) through the perspective of density functional theory: Adjustment of physical characteristics as consequence of strain

The solar technology industry has lately given inorganic perovskite materials an abundance of thought because of their unique optical, electrical and structural characteristics. Issues pertaining to lead (Pb) toxicity and instability require being referred to promptly, making lead-free atomically designed metal halide perovskites of foremost importance to the photovoltaic and optoelectronic industries. Perovskites, a class of inorganic metal halide semiconductors, have variant similarities with Mg3SbX3 (X = I, Br, Cl and F). According to the space group Pm-3m Mg3SbX3 (X = I, Br, Cl and F) has a cubic perovskite crystal structure. Utilizing first-principles density-functional theory (FPDFT), The intention of this investigation is to analyze how strain and spin-orbit coupling (SOC) impact the structural, electrical, optical and mechanical features of the inorganic cubic perovskite of Mg3SbX3 (X = I, Br, Cl and F). At the point between R and Γ, the Mg3SbI3,Mg3SbBr3,Mg3SbCl3 molecule displays an indirect bandgap of 0.105 eV, 0.957 eV, 1.728 eV. At the Γ point, the Mg3SbF3 molecule displays a direct bandgap of 3.184 eV. The bandgaps of the Mg3SbI3,Mg3SbBr3,Mg3SbCl3 and Mg3SbF3 perovskites are 0.198 eV, 1.203 eV, 1.901 eV and 3.723 eV respectively, when considering the spin-orbital coupling (SOC) quantum influence. A wider bandgap is investigated for increasing compressive strain while a smaller bandgap is observed for increasing tensile strain. Apart from the elastic constants and anisotropic factors, other factors that are anticipated include Pugh's ratio, Poisson's ratio, bulk modulus and others. Isotropic, ductile and mechanically stable are the words that best describe these materials, according to the elastic property evaluations. In the photon energy range that is appropriate for solar cells, the dielectric constant spikes of Mg3SbX3 are found to be visible. Therefore, Mg3SbX3 (X = I, Br, Cl and F) perovskite is a good material to use in solar cells for managing light and producing electricity.

Theoretical Studies of the Electronic and Thermoelectric Properties of PrIn3 and NdIn3 in Cubic Phase

The electronic and thermoelectric properties of AB3 (A =Pr, Nd and B=In) materials (crystallizing in the cubic structure) having space group Pm-3m (221) are studied using B3PW91 hybrid functional through the Full-Potential Linear Augmented Plane Wave (FP-LAPW) approach within the framework of Density Functional Theory (DFT). The calculated lattice parameters for PrIn3 and NdIn3 are 4.5668 Å and 4.5539 Å respectively. Electron-electron correlation effect is due to the 4f orbitals present in these materials and therefore, with the use of B3PW91 hybrid functional, band structure and density of states are calculated. When analyzing electron charge density, these materials showed a stronger ionic character. Band structure and density of state analysis confirms the metallic nature of the materials. Using the semi-empirical Boltzmann approach implemented in the BoltzTraP code, the thermoelectric parameters, such as Seebeck coefficient, figure of merit, electrical conductivity per relaxation time, and electronic thermal conductivity per relaxation time as a function of chemical potential, were computed at 500 K temperature gradient. PrIn3 showed highest Seebeck coefficient value, 50.68 μV/K among these compounds. The peak value of electrical conductivity per relaxation time and electronic thermal conductivity per relaxation time among these compounds is calculated for NdIn3 is 2.43 x 1020 1/Ωms and 22.50×1014 W/mKs.

Thermal-dependent luminescence in Er³⁺-doped BaHfO₃ and SrHfO₃ perovskites: Improve temperature sensing via Ba-Sr exchange

The luminescence process behavior stimulated by temperature changes is examined by using the theory of thermally coupled energy levels of erbium ion (Er3+) 2H11/2 and 4S3/2. The different mechanisms and environments are compared and elucidated in crystalline structures of BaHfO3 and SrHfO3 as a product of the atomic exchange of Ba2+ for Sr2+ respectively. The undoped and erbium-doped materials were synthesized by hydrothermal route, the erbium-doped materials were impurified with different Er3+ concentrations; 0.25, 0.5, 1, 3, and 5 at.%. X-ray diffraction (XRD) patterns of both materials present a cubic perovskite-type phase, with space group Pm-3m. High-resolution transmission electron microscopy (HRTEM) micrographs show for both materials the presence of nanocrystals with straight profiles and with an approximate size of 36 nm for BaHfO3 and 32 nm for SrHfO3. The room temperature photoluminescent emission spectra shows the highest luminescent intensity at 1 % Er3+ for both materials, showing different spectral characteristic shapes for each material, due to the different electrostatic forces produced by either Ba2+ or Sr2+ ions surrounding Er3+. Using the “Fluoresce Intensity Ratio” (FIR) technique, the temperature sensing properties of these materials were analyzed and compared from 290 to 330 K covering the well-known physiological range (298.15 K–318.15 K). Both materials, BaHfO3:1%Er3+ and SrHfO3:1%Er3+, show dependence to temperature changes, and the experimental energy gap (ΔE) was used to improve (or decrease) the temperature sensing properties. The theoretical ΔE, maximum relative sensitivity (SRMAX), and the resolution in temperature (δT) were obtained, for BaHfO3: 1 % Er3+ these values were: ΔE = 505.73 cm−1, SRMAX = 0.87 % K−1 at 288.5 K and δT = 0.02 K, while for SrHfO3: 1 % Er3+ the values were: ΔE = 649.21 cm−1, SRMAX = 1.12 % K−1 at 288.5 K and δT = 0.01 K.

Exploration of Na-based NaXO3 (X = Ge, Si) oxide-perovskites: A density functional theory study

The physical properties of Na-based NaXO3 (X = Ge, Si) oxide-perovskite have been explored within the density functional theory (DFT)-based CASTEP code. Both compounds have a cubic shape with a space group Pm3m. Thestructural stability of these compounds has been assessed byemploying the formation enthalpy computations. Regarding the electronic properties, it was found that NaGeO3 and NaSiO3 are p-typesemiconducting materials with an indirect band gap. The total density of states (TDOS) and partial density of states (PDOS) confirm the amount of electron concentration in specific bands. Both materials absorb light more strongly, in the ultraviolet spectrum. Therefore, we believe these materials are good candidates for electronics and optoelectronic applications associated with collecting UV light. It is also found that the cubic forms of both compounds simplify their mechanical stability. These results not only enhance our understanding of NaXO3 materials but also open up new possibilities for the potential applications of these materials in various technological applications.

Study on the Structure, Morphology, Dielectric, and Piezoelectric Properties of Large-Grain (Ba0.85Sr0.15)1-x Pb x TiO3 Ceramic System for 0.02 ≤ x ≤ 0.08.

Barium strontium lead titanate ((Ba0.85Sr0.15)1-x Pb x TiO3), along with various compositions (x(mol %) = 0, 2, 4, and 8), was synthesized through the conventional sol-gel reaction method. Following this, the resultant powders underwent a carefully controlled calcination process at 1000 °C for a period of 4 h. The examination of the crystalline phase of the calcined ceramics was conducted at room temperature using X-ray diffraction. Rietveld refinement of the XRD data, performed using FullProf, revealed that the samples exhibited a tetragonal structure within the space group P4mm. The impact of Pb doping on the lattice structure of BaSr1-x TiO3 was explored by analyzing the charge density distribution. The FTIR analysis unveiled a distinct absorptive band within the 450-600 cm-1 range, indicative of the stretching and bending vibrations associated with TiO6 octahedra. Notably, sintering the material at 1150 °C for 4 h resulted in improved densification, as observed in scanning electron microscopy images showcasing a nearly uniform distribution of densely packed grains. Through the utilization of Williamson-Hall plots derived from XRD data, the average particle diameter was estimated to fall within the range of 131.87-141 nm, with an associated uncertainty ranging from 5 to 10%. Additionally, the dielectric characteristics unveiled the presence of a negative dielectric constant (εr) spanning the frequency range from 1 kHz to 2 MHz. The (Ba0.85Sr0.15)1-x Pb x TiO3 ceramic displayed a widespread occurrence of negative permittivity, emphasizing the influence of dielectric resonance. The investigation revealed that the sintered ceramic with the formula (Ba0.85Sr0.15)1-x Pb x TiO3 exhibited exceptional piezoelectric properties, achieving the highest piezoelectric constant (d33 = 137 pC/N) and electromechanical coupling factor (k p = 0.49).

Electrical conductivity and relaxation mechanisms of nanocrystalline Ba0.75Ca0.2Cs0.05TiO3

Ca and Cs doped barium titanate lead-free ceramic with the formula Ba0.75Ca0.2Cs0.05TiO3 has been prepared by the solid-state reaction method. X-ray diffraction (XRD) confirms the crystallization of the sample in a tetragonal structure with a P4mm space group. The phase purity and grain morphology were evaluated using X-ray diffraction and scanning electron microscopy (SEM). The material exhibits a primary phase of Ba0.75Ca0.2Cs0.05TiO3 with a minor secondary phase of BaO2, and the average grain size is determined to be 1.66 μm. Using non-destructive complex impedance spectroscopy (CIS), we extensively studied the electrical behavior, including complex impedance (Z*), complex modulus (M*), electrical conductivity, and relaxation mechanisms, of Ba0.75Ca0.2Cs0.05TiO3 over a wide temperature (85 K–290 K) and frequency range. The ac conductivity analysis reveals that the dominant conduction mechanism is the non-overlapping small polaron tunneling (NSPT) model. The impedance analysis indicates a single semi-circle in the real and imaginary parts, suggesting a single relaxation mechanism. Additionally, the activation energy was calculated to be approximately 0.0489 eV. These findings contribute to the understanding of the structural and electrical properties of Ba0.75Ca0.2Cs0.05TiO3, highlighting its potential applications in electronic devices such as capacitors, thermistors, and ferroelectric random access memories (FRAMs).

Effect of pressure on electronic, magnetic, thermodynamic and thermoelectric properties of RbNpF3 perovskite

This paper delves into an examination of the structural, electronic, magnetic, thermal, and transport properties of RbNpF3 perovskite using first-principle calculations within density functional theory (DFT). Employing the Birch Murghanan's equation of state the geometric optimization of structure confirms the cubic configuration with the Pm-3m (No. 221) space group and stability in ferromagnetic phase. Effect of high pressure on electronic and magnetic properties was also studied. Electronic band structure and density of states assessments confirm metallic character over a wide range of pressure. Furthermore, for the examined compound we have calculated the heat capacity, thermal expansion coefficients and Grüneisen parameter by using the Debye model. We have also calculated the different transport parameters like Seebeck coefficient, electrical conductivity, thermal conductivity and power factor as a function of temperature. These parameters indicate the potential application of the material for generating thermoelectric energy.

Insight into the structural, electronic, mechanical, and optical properties of Pb-free new inorganic perovskite Mg3SbX3 (X = I, Br, Cl, F) via first-principles analysis

The structural, electronic, mechanical, and optical properties of lead-free new inorganic halide perovskites of Mg3SbX3 (X = I, Br, Cl, F) have been investigated in detail using DFT calculations in this work. Here, all the compounds exhibit cubic phases with the space group Pm-3m (221). Upon detailed analysis, the Mg3SbI3, Mg3SbBr3, Mg3SbCl3, and Mg3SbF3 perovskites have shown semiconducting behavior with direct band gaps of 0.186 eV, 1.097 eV, 1.655 eV, and 3.460 eV, respectively, making them suitable for solar cell applications. Furthermore, elasticity constants reveal that all four perovskites are brittle, stiff, strong, and mechanically stable. According to optical data examined, there is significant absorption and low losses between 2 eV and 10 eV which is very useful for solar cells and optoelectronic devices.

Doublet doped titanate ferroelectric system for capacitors and NTC thermistor applications

A simple negative temperature coefficient (NTC) thermistor Ba0.85Sr0.15Ti0.85Zr0.15O3 system is elaborated using a conventional solid-state reaction route. The structural analysis confirms that the elaborated pseudo-cubic system, which is indexed in the P4mm space group, exhibits one single phase. The dielectric properties and the electrical resistivity data are investigated over a large temperature range from 413 K to 673 K. In this temperature interval, the Steinhart–Hart equations are employed to confirm that Ba0.85Sr0.15Ti0.85Zr0.15O3 is a promising system for sensor application. Accordingly, the thermistor constant (β=10154 K), the sensitivity factor (-5.5 %/K≤α≤-2 %/K), the activation energy (Ea=0.875 eV), and the stability factor (SF=2.27) parameters are calculated to approve that Ba0.85Sr0.15Ti0.85Zr0.15O3 exhibits an NTC-thermistor behavior. The temperature dependence of the electrical resistivity confirms that Ba0.85Sr0.15Ti0.85Zr0.15O3 reveals a semiconductor behavior. The dielectric investigation shows that Ba0.85Sr0.15Ti0.85Zr0.15O3 exhibits a motivating dielectric properties (elevated dielectric constant value (105<ε’<106) and low dielectric losses (mostly < 0.007) with almost frequency independence between 20 Hz to 500 kHz). The colossal dielectric response of Ba0.85Sr0.15Ti0.85Zr0.15O3 is attributed to the internal barrier layer capacitor (IBLC) and the surface barrier layer capacitor (SBLC) effects. Such response suggests the suitability of Ba0.85Sr0.15Ti0.85Zr0.15O3 ceramic for high temperature capacitor applications.

Effect of Co doped BCT on structural, microstructural, dielectric, and multiferroic properties

The structural, microstructural, dielectric, optical, ferroelectric, and magnetic properties of cobalt doped barium calcium titanate (BCT) (Ba0.80Ca0.20Ti1-xCoxO3 with x = 0.000, 0.005, 0.010, 0.015, and 0.020) ceramics have been reported in this paper. The ceramic samples were prepared by the conventional solid-state reaction method. For all of the prepared samples, the tetragonal structure with the space group P4mm has been confirmed using the refinement method through Rietveld refinement of X-ray diffraction patterns. Field Emission Scanning Electron Microscopy (FESEM) micrographs revealed that the average particle size exists in micrometre range (0.3–0.8) μm. Optical studies revealed a gradual decrease in the energy bandgap from 3.31 eV to 2.71 eV with increasing doping concentration. A decreasing trend was observed in the dielectric characteristics of the material with changing frequencies at room temperature. Ferroelectric (P-E loops) analysis displayed an increase in both remnant polarization and maximum polarization of the ceramic with the increasing applied electric field. The highest value for the energy storage efficiency (η) was calculated to be 20.51 %. Magnetic analysis conducted at room temperature revealed the enhancement in ferromagnetism with the increase in doping concentration.

Novel Sol-Gel Synthesis Route for Ce- and V-Doped Ba0.85Ca0.15Ti0.9Zr0.1O3 Piezoceramics.

To meet the current demand for lead-free piezoelectric ceramics, a novel sol-gel synthesis route is presented for the preparation of Ba0.85Ca0.15Ti0.9Zr0.1O3 doped with cerium (Ce = 0, 0.01, and 0.02 mol%) and vanadium (V = 0, 0.3, and 0.4 mol%). X-ray diffraction patterns reveal the formation of a perovskite phase (space group P4mm) for all samples after calcination at 800 °C and sintering at 1250, 1350, and 1450 °C, where it is proposed that both dopants occupy the B site. Sintering studies show that V doping allows the sintering temperature to be reduced to at least 1250 °C. Undoped BCZT samples sintered at the same temperature show reduced functional properties compared to V-doped samples, i.e., d33 values increase by an order of magnitude with doping. The dissipation factor tan δ decreases with increasing sintering temperature for all doping concentrations, while the Curie temperature TC increases for all V-doped samples, reaching 120 °C for high-concentration co-doped samples. All results indicate that vanadium doping can facilitate the processing of BCZT at lower sintering temperatures without compromising performance while promoting thermal property stability.

Synthesis and characterization of Eu3Ba5Cu8O18-δ superconductor doped with 0.1% Graphene oxide

This research presents the synthesis and evaluation of the structural and morphological properties of superconducting Eu3Ba5Cu8O18-δ doped with 0.1% graphene oxide, using the solid state reaction method. The structural analysis performed on the samples, both doped and undoped, allowed identifying the main phase as Eu3Ba5Cu8O18-δ (Eu358), with orthorhombic structure and space group Pmm2(25), maintaining superconducting properties in both cases. In addition, it was observed that doping with graphene oxide resulted in the formation of a minority phase of EuBa4Cu3O9 (Eu143), with cubic structure and space group P23(195). As for the morphological characterization, it was evidenced that the undoped sample presents aggregates formed by non-uniform size grains, with an average size of approximately 97 µm. In contrast, the sample doped with 0.1% graphene oxide exhibits significant improvements in uniformity and grain boundaries, with an average size of about 141 µm. These results confirm obtaining Eu3Ba5Cu8O18-δ with a 73% superconducting phase, exceeding the percentages previously reported using the solid-state reaction method.

Dielectric study and electrochemical detection of ascorbic acid using modified electrode treated with europium-doped tricalcium aluminate nanoparticles

The current study involved the dielectric, and sensor properties of trivalent europium (Eu3+) doped tricalcium aluminate (Ca3Al2O6) Nanoparticles. These samples were synthesized through the solution combustion method with urea (NH2CO·NH2) as the fuel. Structural analysis confirms that the samples exhibited a sustainable cubic phase with the Pm-3m space group. The irregular spherical morphology and agglomeration of synthesized particles were observed using a scanning electron microscope. The energy bandgap values were calculated using the Kubelka and Munk relation, which ranged from 5.14 to 5.27 eV. To examine the dielectric behavior at different frequencies, electrical impedance spectroscopy was performed which provided insights into the changes in electrical permittivity and revealed the contributions of both grains and grain boundaries in the samples. The synthesized material exhibited higher values of dielectric constant and loss at lower frequencies, which decreased significantly as the frequency increased. This suggests that the samples are suitable for applications in microwave devices. Also, the electrochemical studies demonstrate the sensor's rapid amperometric response to ascorbic acid oxidation. The current constructed sensor has a sensitivity of 0.0065 A for ascorbic acid and the electrode treated with Ca3-xAl2O6:xEu3+ (x = 0.05) is better able to detect the electrochemical behavior of substances like ascorbic acid.

TPO12-graphene: A new two-dimensional metallic carbon with 4–5 ring for Lithium ion battery

For many decades, the stability of two-dimensional carbon structures involving connected 4–5 ring remained speculative. Recently, some of the planar carbon structures with connected 4–5 ring have showcased possible stability. In this work we present a new 4–5 ring carbon structure, belonging to Pmmm space group, having additional octagonal and dodecagonal rings to fill the space. The stability of this structure has been ensured in terms of its dynamical, thermal and mechanical stability. The electronic structure indicates that it is a non-magnetic metallic material. Moreover, the Fermi surface points to distinct electron and hole pockets in the first Brillouin zone. The quantum capacitance of the material suggests its use as anode in asymmetric supercapacitors. Besides its low optical absorption in visible range, its potential as an anode material for lithium-ion batteries is worth exploring. The storage capacity results of 558 mAh/g for the new material may be encouraging for its application as a lithium-ion battery anode material.

Co-relation between Rietveld analysis, dielectric studies and impedance spectroscopy of the Ba1−xSrxTiO3 ceramics

Barium strontium titanate (BST), with varying Sr doping levels (x = 0, 0.05, 0.075, 0.1, 0.15, 0.3), was successfully synthesized using the solid-state reaction technique. The aim was to investigate the microstructural, dielectric, and impedance properties as Sr doping increases. X-ray diffraction analysis revealed a tetragonal phase structure for these materials, belonging to the P4mm space group, confirmed via Rietveld refinement using the Fullprof suite. SEM analysis indicated the decrement in grain sizes ranging from 0.198 to 0.0582 μm as doping concentration increases. The temperature and frequency dependencies of the dielectric constant were examined, with the Curie temperature observed in the range of 295 to 351 K with decreasing trend with substitution of strontium in pure barium titanate, showing an increase in dielectric constant with rising temperatures and non-relaxor behavior. P–E loops of BST samples illustrated bulk ferroelectric behavior, with maximum values of retentivity and coercivity reaching 1.56 and 13.97, respectively, in the highly doped BST sample. Various analytical techniques, including Nyquist plots, real and imaginary components of impedance, conductivity measurements, modulus formalism, and determination of charge carrier activation energy, were employed to elucidate the relationships between microstructure and electrical properties. Temperature-dependent resistivity demonstrated the negative temperature coefficient of resistance (NTCR) behavior in Sr-doped barium titanate. Impedance studies revealed semicircular arcs in Nyquist plots, indicating contributions from both grains and grain boundaries. The formation of well-defined grains in the BST samples was further confirmed through modulus spectroscopy.