Space Group Pm3m Research Articles

Alkaline earth based antiperovskite AsPX3 (X = Mg, Ca, and Sr) materials for energy conversion efficient and thermoelectric applications

Antiperovskite were created by swapping ionic positions in the perovskite ABX3 crystal composition. These have great potential for renewable energy devices owing to their low band gap, low cost, and high absorption with Pm-3m space group. Herein, the authors have investigated inherent properties such as bulk modulus and its pressure derivatives, lattice constant, the density of states, band gap, effective mass, refractive index, dielectric constant, extinction coefficient, and absorption coefficient, thermoelectric parameters etc of antiperovskite materials by using density functional theory-based first-principles calculations. These materials exhibit high absorption in the Visible, Ultraviolet region and also in the Near Infrared region which is the most admirable property acquired by various Optoelectronic devices. The proposed compounds have been found mechanically and thermodynamically stable. Their high figure of merit makes them a potential candidate for thermoelectric devices. The proposed material AsPCa3 with a theoretical efficiency of 34% is expected to be a good photovoltaic absorber material.

Synthesis and Characterization of a New Alginate/Carrageenan Crosslinked Biopolymer and Study of the Antibacterial, Antioxidant, and Anticancer Performance of Its Mn(II), Fe(III), Ni(II), and Cu(II) Polymeric Complexes.

Natural polysaccharides are essential to a wide range of fields, including medicine, food, and cosmetics, for their various physiochemical and biological properties. However, they still have adverse effects limiting their further applications. Consequently, possible structural modifications should be carried out on the polysaccharides for their valorization. Recently, polysaccharides complexed with metal ions have been reported to enhance their bioactivities. In this paper, we synthesized a new crosslinked biopolymer based on sodium alginate (AG) and carrageenan (CAR) polysaccharides. The biopolymer was then exploited to form complexes with different metal salts including MnCl2·4H2O, FeCl3·6H2O, NiCl2·6H2O, and CuCl2·2H2O. The four polymeric complexes were characterized by Fourier-transform infrared spectroscopy (FT-IR), elemental analysis, ultraviolet-visible spectroscopy (UV-Vis), magnetic susceptibility, molar conductivity methods, and thermogravimetric analysis. The X-ray crystal structure of the Mn(II) complex is tetrahedral and belongs to the monoclinic crystal system with the space group P121/n1. The Fe(III) complex is octahedral and crystal data fit with the cubic crystal system with the space group Pm-3m. The Ni(II) complex is tetrahedral and crystal data correspond to the cubic crystal arrangement with the space group Pm-3m. The data estimated for the Cu(II) polymeric complex revealed that it is tetrahedral and belongs to the cubic system with the space group Fm-3m. The antibacterial study showed significant activity of all the complexes against both Gram-positive bacteria (Staphylococcus aureus and Micrococcus luteus) and Gram-negative (Escherichia coli and Salmonella typhimurium) pathogenic strains. Similarly, the various complexes revealed an antifungal activity against Candida albicans. The Cu(II) polymeric complex recorded a higher antimicrobial activity with an inhibitory zone reaching 4.5 cm against Staphylococcus aureus bacteria and the best antifungal effect of 4 cm. Furthermore, higher antioxidant values of the four complexes were obtained with DPPH scavenging activity varying from 73 to 94%. The two more biologically effective complexes were then selected for the viability cell assessments and in vitro anticancer assays. The polymeric complexes revealed excellent cytocompatibility with normal human breast epithelial cells (MCF10A) and a high anticancer potential with human breast cancer cells (MCF-7) which increase significantly in a dose-dependent manner.

Enhanced room temperature relative permittivity and low dielectric loss ferroelectric double perovskite for energy storage applications

The polycrystalline ceramic oxide, BaBi1.2Fe0.8TiO6 is synthesized by a mixed oxide method at 1000 °C. XRD and Rietveld's analysis suggests a tetragonal system and P4mm space group. The closely spaced dense micro grains of various shapes and sizes in scanning electron micrograph (SEM) image support the polycrystalline single-phase compound. The UV–Visible spectroscopy results in a convenient value of threshold wavelength (610 nm), absorption bandgap energy (2.23 eV), and reflectance bandgap energy (2.31 eV) which are good responses to the IR and visible range and its possible application in photocatalytic devices. The room temperature (RT) polarization loop shows non-zero remanent polarization, i.e. ferroelectric property of the compound. Relatively higher room temperature dielectric permittivity (ɛr = 2455) with low loss tangent (tanδ) = 0.247 at 100 Hz, phase transition (Td > 200 °C), and Curie (Tc > 470 °C) temperature values are supporting to be as good dielectric material for ceramic capacitors. Transport property shows lower RT current density is in order of 1E-9 at 300 V/cm. The compound follows the Arrhenius equation and results in imminent values of activation energy in ac conductivity (Ea = 0.847 eV at 100 Hz) and dc conductivity (Ea = 0.838 eV) analysis. Based on the results, the present compound is likely to be used as a dielectric material in ceramic capacitors, energy and memory storage devices, and photocatalytic devices.

The effect of charged defects on the local effective piezo-electric response for the polycrystalline lead-free BCZT bulk ceramic versus thin film

The current work presents the d33,eff evaluation for Ba0·9Ca0·1Ti0·9Zr0·1O3 (BCZT) thin film (TF) prepared by RF magnetron sputtering over Pt (111) substrate by switching spectroscopy piezo-response force microscopy (SS-PFM). Our results reveal an d33.eff approximately of 70 p.m. V−1. This value was compared with the bulk ceramic counterpart (d33.eff = 72 p.m. V−1), and it is comparable with other similar lead-free TF compositions. To understand the d33.eff value for the TF, the influence of mixed-valence Ti (Ti3+ and Ti4+) states and oxygen chemical ions is elucidated by x-ray photoelectron spectroscopy (XPS). The component analysis for Ti 2p and O 1s XPS regions confirmed a less presence of oxygen O− ions in the TF. X-ray diffraction corroborates the tetragonal perovskite structure with P4mm space group, which is desired to obtain ferroelectric properties. The good piezo-response for the TF is very promising as a storage device for the electronic industry.

Effects of (Ba,Ca)ScO2F:Bi3+,K+ phosphor particle size on color uniformity white light-emitting diodes

Phosphors that offer considerable performance as well as heat consistency has been a high priority of recent studies concerning light-emitting diodes (LED) devices. This study employs the perovskite phosphors BCSOF (short for Ba<sub>1-x</sub>Ca<sub>x</sub>ScO<sub>2</sub>F:0.001Bi3+,0.001K+ with x value from 0 to 0.12 and one chip at 415 nm generating thin green illumination via cation-replacement method. The study examines the aftermath when Ca<sup>2+</sup> replaces Ba<sup>2+</sup> within the crystal formations of BCSOF as well as the luminescent features of the phosphors, detecting a formation of cube-like perovskite within the space group of Pm3m in the employed phosphors. In addition, the study also assesses the development concerning the magnitude of cells as well as the binding extent of Ba/Ca/K/Bi-O. When the inner quantum performance reaches 77.4% in BCSOF, a potent green discharge is manifested, reaching 510 nm when excited by a chip at 415 nm. Greater luminescent performance as well as heat consistency correlating with changes in inner formation were reported. Via the method of replacing cations, it is possible to control spectrum by manipulating the latticework’s surroundings, leading to desirable performance in LED products.

Study of the structural and electrical properties of the compound (Ba0.99Ca0.01)(Ti0.8−xZr0.2)MnxO3 for x = 0.25%

The material (Ba0.99Ca0.01)(Ti0.8−xZr0.2)MnxO3 for x = 0.25 % is obtained by a conventional solid-state reaction method. It is analyzed in terms of structure, Raman spectra, thermal and electrical properties. It is crystallized in an orthorhombic system of space group Pmmm. The vibrational properties of the material were studied by Raman spectroscopy at room temperature, showing that there is a band around 670 cm−1 sign of the orthorhombic structure.The electrical properties of this compound were studied by complex impedance spectroscopy in the frequency range 100 Hz 100 MHz and temperatures range 450–700 K. The impedance plot indicates the presence of two relaxation processes in this compound, associated with the grain and the grain boundary. The measured AC conductivity follows the typical power-law dependence on charge transport. Therefore, the experimental results are analyzed using various theoretical models.

Synthesis and characterization of (Co1-x Nix)3(BTC)2.12H2O (0 ≤ x ≤ 0.5) MOF based Janus chemical micromotors

We report the synthesis and characterization of Metal–Organic Framework (MOF)-Based Janus chemical Micro motors that self-propel at 26 and 25 µms−1 in 5% and 12% of H2O2, respectively, via ionic diffusiophoresis. The synthesis of this MOF was achieved by solvothermal method. The TG -DT analysis study on (Co1-x Nix)3(BTC)2·12H2O (0 ≤ x ≤ 0.5) micro motors, showed that water ligands can be easily removed. The Co3(BTC)2·12H2O crystallized in orthorhombic crystal system with Pmmm space group and (Co0.8Ni0.2)3(BTC)2·12H2O, (Co1.5Ni1.5)3(BTC)2·12H2O crystallized in monoclinic crystal system with C2 space group. The lattice constants, dislocation density and micro strain of the micro motors were calculated and the structure is discussed in detail using crystal viewer. The morphology of (Co1-x Nix)3(BTC)2·12H2O (0 ≤ x ≤ 0.5) micro motors were scrutinized using the field emission scanning electron microscopy (FE-SEM). Energy dispersion X-ray (EDX) analysis was employed for the elemental analysis and chemical characterization. The vibrational characterization was studied by utilizing Fourier Transform Infrared Spectroscopy (FT-IR) and Raman spectroscopy. The asymmetric and symmetric stretching vibrations of 1,3,5 trisubstituted aromatic ring appeared as three bands at 1368, 1428 and 1219 cm−1. The optical properties were explored using UV–Visible DRS and the absorption edge of Co-BTC, Co0.8Ni0.2-BTC and Co0.5Ni0.5-BTC were observed at approximately 300 nm, 450 nm and 500 nm respectively. The direct band gap for (Co1-x Nix)3(BTC)2.12 H2O (0 ≤ x ≤ 0.5) micromotors was found to be 3.84 eV, 3.76 eV and 3.66 eV respectively. The pore-size distribution and specific surface areas were calculated using Barrett–Joyner–Halenda, BJH and Brunauer Emmett-Teller method respectively. The average pore diameter 8.727 nm and total pore volume of 2.467 × 10−2cm3g−1 was obtained for the material. Insertion of nickel in the lattice of cobalt further accelerates the speed from 0.08 µms−1 to 26µms−1, which leads to a force of 7.29 fN and a power of 4.9 × 10−9 fW, which resembles bio molecular motors. Considering the investigation of MOFS as Microbots/Micromotors so far, Co0.8Ni0.2BTC in both 5% and 12% H2O2 can be represented as the best example of clear observation of bubble tails propelling spherical Janus micromotors.

SrTiO3:Pr,Al phosphor mesocrystals: The role of Al-doping in short-range and electronic structure and its influence on photoluminescence properties

Phosphor materials with narrow emission bands and high quantum efficiency have received a good amount of attention, suggesting the possibility of several applications in the field of optoelectronic devices. SrTiO3:Pr is an example of a material with these characteristics. In this study, mesocrystal samples of Sr0.998Pr0.002Ti1−yAlyO3 (SrTiO3:Pr,Al) were prepared via a hydrothermal route, and the morphology presented a microcube shape and pristine structure with Pm3m space group without any spurious phases for all Al concentrations. Measurements of X-ray absorption spectroscopy (XAS) at Ti K-, LII,III-, and O K-edges, calculated projected density of states, and Raman spectroscopy revealed that the hydrothermal method and Al incorporation cause a local symmetry breaking, deviating from the cubic structure, Ti off-center displacement, tilting of TiO6 octahedra, and O vacancies. As the Al content increases, the intensity of some emissions in the photoluminescence spectra also increases up to 3 at%. The disorder produced by Al concentration leads to a lower symmetry around Pr3+ sites, resulting in an increase in the probabilities of transitions for Pr3+ ions due to the mixing of the opposite parity in 4 f configurational levels. On the other hand, higher Al concentrations cause a decrease in the intensity of Pr emissions, which is related to their quenching because of O vacancies. Additionally, intrinsic defects due to the hydrothermal route and Al incorporation generate a broad emission in the photoluminescence spectra. This broad emission is associated with intermediary electronic levels in the band gap caused by these intrinsic defects.

Addressing electrocatalytic activity of metal-substituted lanthanum manganite for the hydrogen evolution reaction

A comparative electrochemical study between unsubstituted LaMnO3 (LMO) and Ca (LMO-Ca) or Pd (LMO-Pd) substituted LaMnO3, synthesized by the sol-gel method, followed by thermal treatment at low temperature was performed. The obtained materials were studied morpho-structural by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), specific surface (BET), transmission electron microscopy (TEM) and semi-quantitative analysis (EDX), and the electrochemical performance was investigated. X-ray diffraction analysis revealed the formation of single-phase compounds with the average crystals size between 18 and 20 nm (calculated from Scherrer equation), crystallized in the cubic structure with Pm-3m space group. The perovskite materials were studied in terms of their electrocatalytic activity for the hydrogen evolution reaction in alkaline medium. Out of the electrodes manufactured using compositions containing the perovskites, the most catalytically active was the one modified from a suspension obtained by adding 2 mg LMO-Pd, 1 mg Carbon Black and 10 µL Nafion solution in 0.5 mL ethanol, and it displayed an overpotential value of 0.49 V at i = -10 mA/cm2 and a Tafel slope value of 161 mV/dec. The analysis performed in this research work reveals that the most significant results were obtained for the Pd-modified materials.

Phase Instability, Oxygen Desorption and Related Properties in Cu-Based Perovskites Modified by Highly Charged Cations

The rock-salt ordered A2CuWO6 (A = Sr, Ba) with I4/m space group and disordered SrCu0.5M0.5O3−δ (M = Ta, Nb) with Pm3m space group perovskites were successfully obtained via a solid-state reaction route. Heat treatment of Ba2CuWO6 over 900 °C in air leads to phase decomposition to the barium tungstate and copper oxide. Thermogravimetric measurements reveal the strong stoichiometric oxygen content and specific oxygen capacity (ΔWo) exceeding 2.5% for Ba2CuWO6. At the same time, oxygen content reveals Cu3+ content in SrCu0.5Ta0.5O3−δ. Under the following reoxidation of Ba2CuWO6, step-like behavior in weight changes was observed, corresponding to possible Cu+ ion formation at 900 °C; in contrast, no similar effect was detected for M5+ cations. The yellow color of Ba2CuWO6 enables to measure the band gap 2.59 eV. SrCu0.5Ta0.5O3−δ due to high oxygen valance concentration has a low thermal conductivity 1.28 W·m−1·K−1 in the temperature range 25–400 °C.

Oxygen non-stoichiometry and mixed conductivity of Ti -doped BaCo0.4Fe0.4Y0.2O3-δ perovskite

The mixed electronic-ionic conducting (MIEC) perovskite materials are promising as a cathode of solid oxide fuel cells (SOFCs). According to recent reports, BaCo0.4Fe0.4Zr0.2O3-δ (BCFZ) and its doped compounds exhibit potentiality under the SOFCs operating conditions at intermediate-low temperatures. The structural, oxygen non-stoichiometry, electrical conductivity, and oxygen permeability properties of Ti-doped BaCo0.4Fe0.4Y0.2O3-δ was characterized and then compared with those of BaCo0.4Fe0.4Y0.2O3-δ or Mg-doped BaCo0.4Fe0.4Y0.2O3-δ. The cubic symmetry with space group Pm-3m crystallizes in all the prepared samples. The Ti-doped sample displayed the highest total electrical conductivity of 3.19 S cm−1 at 800 °C, which is higher than the conductivity of the Mg-doped sample (2.52 S cm−1). The oxygen permeability of Ti and Mg-doped samples are 0.46 and 0.48 μmol cm−2 s−1 at 800 °C, respectively. The obtained MIEC (total electronic and oxygen ion conductivities) is higher compared to the BaCo0.4Fe0.4Y0.2O3-δ (total electrical conductivity of 2.9 S cm−1 and oxygen permeability of 0.26 μmol cm−2 s−1) potential cathode within the intermediate temperature-based SOFCs. Thus, this work proposes that Ti-doped perovskite could be a new cathode candidate for SOFCs, concerning structural stability and high mixed electronic-ionic conductivity.

Antiferromagnetism and Structure of Sr1−xBaxFeO2F Oxyfluoride Perovskites

Recently, a series of oxyfluorides, Sr1−xBaxFeO2F with x = 0, 0.25, 0.50, and 0.75 obtained through a novel synthesis route, were characterized by X-ray and neutron powder diffraction (NPD), magnetization measurements, and 57Fe Mössbauer spectroscopy (MS). The diffraction data revealed random occupancy of Sr and Ba atoms at the A-cation site, and a statistical distribution of O and F at the anionic sublattice of the perovskite-like structure specified in space group Pm-3m. MS spectra analysis consistently indicated the presence of Fe3+ ions at B-site, confirming the Sr1−xBaxFeO2F stoichiometry. Magnetic structure determination from the NPD data at room temperature established G-type antiferromagnetic arrangement in all compositions with Fe3+ moments of about 3.5 μB oriented along the c axis. In this study, we present and analyze additional NPD data concerning the low-temperature chemical and magnetic structure of Sr0.5Ba0.5FeO2F (x = 0.5) and SrFeO2F (x = 0). Basically, the three-dimensional G-type magnetic structure is maintained down to 2 K, where it is fully developed with an ordered magnetic moment of 4.25(5) μB/Fe at this temperature for x = 0.5 and 4.14(3) μB/Fe for x = 0. The data processing is complemented with a new approach to analyze the temperature dependence of the magnetic order TN on the lattice parameters, based on the magnetic hyperfine fields extracted from the temperature-dependent MS data.

Melansonite, (Na,□)□2KZrSi8O19·5H2O, a New Member of the Rhodesite Group, from Mont Saint-Hilaire, Québec, Canada: Characterization, Crystal-Structure Determination, and Origin

Abstract Melansonite, ideally (Na,□)□2KZrSi8O19·5H2O, is a new mineral discovered at the Poudrette Quarry, Mont Saint-Hilaire, Québec, Canada. It develops as loose clusters of square to rectangular, euhedral plates with average dimensions of 35 × 50 μm. Individual crystals are ∼2 μm in thickness, dominated by the pinacoid {100}, and colorless to pale yellow in color. Associated minerals include albite, calcite, aegirine, quartz, gaidonnayite, a sodic clinoamphibole, an apophyllite-group mineral, and pyrrhotite (?). Melansonite has a vitreous luster, is transparent, and has a white streak. It exhibits a perfect {100} cleavage, is brittle, and has an irregular fracture. The mineral shows a green fluorescence under short-wave radiation. The calculated density is 2.352 g/cm3. Optically, it is non-pleochroic and presumed to be optically biaxial, with α = 1.536(1), β = 1.537(1), γ = 1.538(1) (for λ = 590 nm), 2Vcalc = 89.9(1)°. No dispersion was noted. The optical orientation is inferred to be Z = b, Y = c, Z = a, based on the observed symmetry and crystal morphology. An average of 15 electron microprobe analyses gave Na2O 2.82, Al2O3 6.32, SiO2 53.50, SO3 0.91, K2O 2.64, CaO 1.75, MnO 1.09, Fe2O3 0.46, Y2O3 0.07, ZrO2 15.41, BaO 1.35, H2O (calc.) 11.32, total 97.64 wt.%. The empirical formula (based on 24 anions) is: (Na0.63Ca0.25Mn0.12)Σ1.00(□1.91Na0.09)Σ2.00(□0.48K0.45Ba0.07)Σ1.00(Zr0.99Fe0.05Y0.01)Σ1.05(Si7.08Al0.99S0.09)Σ8.16O19·5H2O. The mineral is orthorhombic, crystallizing in the space group Pmma (No. 51), with a = 24.063(5), b = 6.9820(14), c = 6.5260(13) Å, V = 1096.4(4) Å3, Z = 2. The strongest six lines of the X-ray powder-diffraction pattern [d in Å (I) (hkl)] are 11.988 (100) (200), 3.060 (29) (121), 6.971 (27) (010), 2.881 (25) (321), 6.529 (19) (001), 3.429 (15) (601). A Raman spectrum is presented; it is very similar to that of monteregianite-(Y), with shifts between the two minerals being consistent with Zr ↔ Y substitution. The crystal structure was refined to R = 5.39%, wR2 = 15.45%. It is strongly layered, with a motif based on double sheets of tetrahedra (T), single sheets of octahedra (O), and extra-framework cations. Double layers of tetrahedra (T) are composed of both eight- and four-membered rings of corner-sharing (Si,Al)O4 tetrahedra that form infinite sheets on (100). Individual layers of the double sheet are joined via branching Si(2) tetrahedra along [100]. Channels created by eight-membered rings of (Si,Al)O4 tetrahedra are occupied by Na, K, and H2O groups. The O layers are composed of edge-sharing Mϕ6 (M = Zr, Na, ϕ = O2−, H2O) octahedra that form infinite sheets on (001). Alternating T and O layers give rise to a TOT topology reminiscent of that observed in micas and characteristic of minerals, including rhodesite, delhayelite, hydrodelhayelite, and monteregianite-(Y), with which melansonite shares a crystal-chemical relationship. Melansonite is paragenetically a late-stage mineral that is considered to have formed as a result of the interaction of late-stage alkaline fluids, enriched in SiO2 and ZrO2, that interacted with a marble xenolith under conditions of low P and T (<200 °C).

Giant low-field reversible magnetocaloric effect at liquid helium temperature of niobium and iron co-substituted EuTiO3 compounds

Giant magnetocaloric effect (MCE) materials in the liquid helium temperature region have attracted a lot of attention in the field of low-temperature magnetic refrigeration (MR). In this study, a series of niobium (Nb) and iron (Fe) co-substituted EuTiO3 perovskites with cubic structure (space group pm3m) was successfully fabricated, and their magnetic properties as well as cryogenic magnetocaloric effects were investigated in detail. As expected, the introduction of Nb and Fe can significantly modulate the magnetic phase transition and magnetocaloric effect of the EuTiO3 compounds. With increasing Fe concentration, two local minima corresponding to the AFM-FM magnetic phase transition near 5.0 K and FM-PM transition near 10 K with no hysteresis in the thermomagnetic curves are observed, which is attributed to an enhancement of FM coupling. At the same time, the gradually widened –ΔSM–T curves and the two peaks with a broad shoulder lead to considerable refrigeration capacity (RC). With the field change of ΔH = 2 T, the calculated values of −ΔSMmax for the EuTi0.9375–xNb0.0625FexO3 (x = 0.075, 0.1, 0.125, 0.15) compounds are 24.2, 17.6, 14.5 and 14.0 J/(kg·K), respectively. The corresponding RC values were calculated to be 144.6, 138.3, 151.2 and 159 J/kg, respectively. Especially, the values of −ΔSMmax for EuTi0.8625Nb0.0625Fe0.075O3 are 8.6 and 15.1 J/(kg·K) under low field changes of 0.5 and 1 T, respectively. The giant low-field reversible magnetocaloric effect makes them attractive candidates for magnetic refrigeration in the liquid helium temperature region.

Monte Carlo Simulation for Investigating the Sintering Temperatures Effects on Radiation Shielding Performances of Lead-Free ABO3 Perovskite Ceramic

In this study, a series of barium titanate ceramics of the chemical composition BaTiO3 was prepared. The solid-state reaction route was adopted to synthesize the ceramic samples at various sintering temperatures of 1100–1300 °C. X-ray diffraction and FTIR spectroscopy were utilized to examine the structure of the fabricated ceramics. The UV–Vis–reflectance data were recorded to guess the optical bandgap energy of the synthesized ceramics. The ability of the synthesized ceramics to attenuate ionizing radiation was qualified using a Monte Carlo simulation (MCNP code) in the γ-energy interval ranging between 59 keV and 1408 keV. Shielding parameters, including LAC, TF, and RPE, were evaluated. The XRD and FTIR analyses showed the formation of a tetragonal BaTiO3 perovskite structure with the Pmmm space group. The crystallite size and the relative density increased, whereas the porosity decreased, with increasing sintering temperatures. Optical bandgap energy (Eg) values decreased as the sintering temperatures increased. The radiation shielding results depicted that raising the sintering temperature between 1100 °C and 1300 °C resulted in a slight increase in the µ values by a factor of ≈8 %. The mentioned increase in the µ values caused a reduction in the Δeq and Δ0.5, and TF values for the fabricated BaTiO3 ceramic samples, while the RPE values increased with increasing sintering temperatures between 1100 °C and 1300 °C.

Functionality and Activity of Sol-Gel-Prepared Co and Fe co-Doped Lead-Free BTO for Thermo-Optical Applications.

The BTO, BFTC, and BCTF compounds were synthesized by the sol-gel method. The XRD study revealed the formation of single-phase tetragonal perovskite structures with the space group (P4mm). The crystalline parameters were studied as a function of Fe and Co contents and occupation of Ba and/or Ti sites by Fe and Co in the BTO lattice. It was found that the obtained strain increases when Ba2+ is substituted by Co2+ and Ti4+ by Fe3+. The Raman investigation confirmed the existence of three active modes (B1/E (TO1LO), (E (TO)/A1(TO3), and (A 1(LO)/E (TO), all of which are related to the existence of the tetragonal phase and strongly support the XRD results. The microstructural study showed a clear correlation between the presence of Fe and Co and the grain size distribution. Optical studies revealed the improvement in band gap energy with transition-metal (Fe and Co) co-doped BTO ceramics. The decrease in the band gap is explained by the competing effects of Columbian interactions, microdeformation, and oxygen defects. The results indicate that the presence of Fe and Co dopants enhances the absorption in the BTO ceramic. The dopants demonstrated an effect on thermal conductivity: they decreased the thermal conductivity of BTO, which is in the range of 0.76-2.23 W m-1 K-1 at room temperature and 2.02-0.27 W m-1 K-1 at elevated temperatures. The microstructure of the manufactured materials and the grain size distribution affect the compressive strength.

Structural analysis of Ba0.8Sr0.2Ti0.6Zr0.3Mn0.1O3 ceramics

Polycrystalline Ba0.8Sr0.2Ti0.6Zr0.3Mn0.1O3 was synthesized by solid-state reaction at 1600°C. The single phase formation of the compound without any impurities was confirmed by the X-ray diffraction technique. The prepared compound crystallized to a cubic structure with a space group of Pm-3m and the refined lattice parameters were a = b = c = 4.0253 Ǻ, α = β = γ = 90°. Rietveld refinement was carried for the powder XRD data using GSAS software and the experimental data peaks were indexed by Powder X software.

The effect of Mg2+ substitution cation on structural and dielectric properties of SrTiO3 sintered ceramics

We have fabricated (Sr1-xMgx)TiO3, (x = 0.00 & 0.3) sintered ceramics by mixed oxide route and studied the structural and microwave dielectric property of the samples with respect to variation of frequency (1 GHz to 2 GHz) using Impedance spectroscopy. This study revealed that the XRD patterns shown cubical structure along with space group (Pm-3m) while SEM images shown spherical like grains of the samples. The microwave dielectric properties of the samples vary with Mg2+ dopants and operating frequency as well. The distinctive absorption peak of hydroxyl vibration at 1350 cm−1 was observed for both samples while hydroxyl vibrational mode was also observed only in doped sample at 3000 cm−1. The microwave dielectric properties strongly depend upon Mg2+ contents and resonating frequency. The optimum microwave dielectric properties have been recorded which may help for the application of microwave wireless communication devices.

Effect of frequency on the classical and relaxor ferroelectric behavior of substituted titanate Ba0.7Er0.16Ca0.05Ti0.91Sn0.09O3.

In the present work, we synthesized the perovskite Ba0.70Er0.16Ca0.05Ti0.91Sn0.09O3 compound (BECTSO) by a solid-state reaction and sintering at 1200 °C. The effects of doping on the structural, electrical, dielectric, and ferroelectric characteristics of the material are examined in this work. X-ray powder diffraction analysis shows that BECTSO crystallizes in a tetragonal structure with space group P4mm. A detailed study of the dielectric relaxation of the BECTSO compound has been reported for the first time. Classical low-frequency ferroelectric and high-frequency relaxor ferroelectric behaviors have been studied. The study of the real part of the permittivity (ε') as a function of temperature demonstrated a high dielectric constant and identified a phase transition from the ferroelectric phase to the paraelectric phase at Tc = 360 K. The analysis of conductivity curves shows two behaviors: semiconductor behavior for f < 106 Hz and metallic behavior for f >106 Hz. The relaxation phenomenon is dominated by the short-range motion of the charge carriers. The BECTSO sample could be considered as a potential lead-free material for next-generation non-volatile memory devices and wide-temperature range capacitor applications.

Crystal structure, chemical bond characteristics, and microwave dielectric properties of novel Sr2CaMoO6 ceramic at different sintering temperatures

This work prepared a novel Sr2CaMoO6 (SCM) ceramic through the conventional solid-state process. The crystal structure, chemical bond characteristics, and microwave dielectric properties of SCM ceramic were investigated for the first time. The X-ray diffraction patterns and Rietveld refinement indicate that SCM ceramic formed an orthorhombic phase with the space group Pmm2 (25) at temperatures above 1300 °C. The lattice vibrational modes of SCM ceramic were obtained through the Fourier transformed infrared spectrum (FTIR). The measured dielectric constant and dielectric loss of SCM ceramic is close to the theoretical values obtained by FTIR. According to the P–V–L theory, the chemical bond characteristics of SCM ceramic were calculated. The high ionicity and lattice energy of the Mo–O bond positively affect the properties of SCM ceramic. The outstanding microwave dielectric properties of εr = 19.37, Q·f = 32,970 GHz (at 5.96 GHz), and τf = −32.56 ppm/°C were obtained in SCM ceramic sintered at 1450 °C. This work reveals the crystal structure of SCM ceramic, establishes the relationship between the properties and chemical bonds of the ceramic, and lays a foundation for studying the dielectric properties of related ceramic systems.