Room Temperature X-ray Diffraction Data Research Articles

NASICON-type medium entropy Li1.5Sn1.0Al0.5Zr0.5(PO4)3 electrolyte for solid state Li metal batteries

Developing solid electrolytes for all-solid-state lithium batteries with superior performance is crucial for portable energy storage. This study uses a traditional solid-state reaction technique to fabricate a NASICON-type medium entropy Li1.5Sn1.0Al0.5Zr0.5(PO4)3 (LSAZP) ceramic electrolyte. The Rietveld refinement of room temperature X-ray diffraction (XRD) data confirms a pure rhombohedral phase (R3‾c) for LSAZP ceramic sintered at 1050 °C. Temperature-dependent synchrotron XRD data demonstrates an increase in lattice parameter c with a positive coefficient of thermal expansion (+2.40 × 10−5 K−1) and a negative coefficient of thermal expansion (−1.26 × 10−6 K−1) for the lattice parameter a with increasing temperature. Interestingly, despite the anisotropic thermal expansion, no intergranular cracks, typically observed in rhombohedral NASICON-type phases, are noticeable in the scanning electron micrographs of the LSAZP samples. The sample sintered at 1050 °C (relative density ∼90 %) exhibits an excellent room temperature conductivity of ∼2.95 × 10−4 S cm−1 and activation energy ∼0.39 ± 0.02 eV. The Li-ion transference number is ∼0.99, suggesting that Li-ion is the dominant charge carrier in the sample. During galvanostatic lithium plating-stripping tests, the symmetric Li|LSAZP|Li cell demonstrates excellent lithium plating-stripping stability over 50 h at a current density of 4 μA cm−2.

Structural, magnetic and transport properties of FeRuVZ (Z = Si, Ge) Heusler alloys: Experiment and theory

Heusler alloys based on 4d-elements are relatively less explored though they are known to host interesting electronic/magnetic properties useful for future spintronics applications. Here, we report a comparative study of the structural and magnetic properties of FeRuVSi (FRVS) and FeRuVGe (FRVG) using experimental and theoretical tools. Magneto-transport measurements have also been carried out to probe the role of magnetism on their transport behaviour. Room temperature (T) X-ray diffraction data reveals cubic crystal structure (space group No. 216) with B2 type antisite disorder between Fe and Ru sites in both the alloys. They show ferromagnetic behaviour below the Curie temperature (TC) 84 K for FeRuVSi and 57 K for FeRuVGe respectively. The field dependence of magnetization at low-T shows saturating (nearly saturating) behaviour for FRVS (FRVG). Transport measurements show metallic behaviour with a sharp reduction in the resistivity near TC. Ab-initio calculations predict nearly half metallic behaviour with ∼ 87 % and ∼ 89 % spin polarization for FRVS and FRVG in their ordered states. The inclusion of antisite disorder changes the magnetic configuration, leading to a visible decrease in the magnetic moment and spin polarization. The calculated net moment and the transport properties agree fairly well with those observed experimentally. These results confirm the importance of disorder in determining the intrinsic properties of these alloys. Such combined studies help in the identification of more novel quantum materials suitable for future spintronic applications.

Electrical resistivity and magnetoresistance of Sr3Fe2+xMo1–xO9–3x/2 (x = 0.45, 0.60, and 1.00) prepared by the solid-state reaction

In this paper, we focus on understanding the behavior of the temperature dependence of electrical resistivity (ρ) and magnetoresistance (MR) in Sr3Fe2+xMo1–xO9–3x/2 perovskites with x = 0.45, 0.60, and 1.00. Three polycrystalline materials were synthesized using conventional solid-state reaction techniques. Rietveld analysis of room-temperature X-ray diffraction data reveals that all three compositions crystallize in tetragonal symmetry; where x = 0.45 and 0.60 undergo an I4/mcm space group, while x = 1.00 adopts a P4/mmm space group. Electrical resistivity measurements carried out at magnetic fields (0 and 1 T) reveal the presence of a transition from the ferromagnetic phase to the paramagnetic phase in the vicinity of the TMI. The metal-insulator transition temperature (TMI) decreases with increasing Fe content and rises slightly with changing magnetic field from 0 to 1 T. The magnetoresistance (MR) of the SrFeO3–δ sample (x = 1.00) has a large value of about 63.6 %, indicating that it can be exploited for certain devices. A variety of theoretical models are used to study the behavior of electrical resistivity in various temperature ranges, showing excellent agreement with experimental results.

Anomalous Nernst effect and thermal conductivity in Co3Sn2S2 polycrystals

A polycrystalline sample of Co3Sn2S2 shandite was synthesized using spark plasma sintering for its densification. The unit cell parameters, a = 5.3688(1) Å and c = 13.1797(1) Å, refined from room temperature X-ray diffraction data, confirm the R-3m shandite structure. The frustrated nature of the Co magnetic network is invoked to explain the low effective paramagnetic moment of Co, μeff = 1.04μB/Co, whereas the ferromagnetic Curie temperature, TC = 175K, determined from T-dependent magnetic susceptibility corresponds to the metal to metal transition at that temperature. Interestingly, the residual resistivity ratio and resistivity values indicate that the electronic transport is driven by the in-plane contribution. This behaviour close to that of ab-plane transport of Co3Sn2S2 crystal fits well with the measurement of an anomalous Nernst effect (ANE). The latter reaches at T = 100K a maximum value Sxy = +1.5 μV K−1, i.e. a reduction by a factor of ≈2 as compared to crystal, explained by the reduction for the magnetization, M, of the former. This is also demonstrated by the H-dependent Sxy and M loops that match very well. Similarly, a hysteresis is found for the thermal conductivity demonstrating the existence of an anomalous thermal Hall effect of about 5 % of the total thermal conductivity. This study shows that ANE can be also measured in ceramics of Weyl ferromagnets.

Tuning of the magneto-caloric effects in Ni43Mn46In11 magnetic shape memory alloys by substitution of boron

In this study, we report the structural, magnetic, and magnetocaloric properties of B substitution on the Mn site in Ni43Mn46−x B x In11(x = 0.5, 1.0) Heusler alloys. Crystal structure analysis using room-temperature x-ray diffraction data reveals both samples have mixed phases composed of cubic and tetragonal phases. The structural and magnetic phase transition characteristic temperatures are determined using differential scanning calorimetry, isothermal magnetization (MT), and isofield magnetization (MH) measurements. Both alloys exhibit inverse and direct magnetocaloric effects in the vicinity of their magnetostructural transition and Curie temperature (T C), respectively. For Ni43Mn45.0B1.0In11 a maximum magnetic entropy change of 25.06 J kg−1 K−1 is observed at 250 K for a magnetic field change of 5 T.

Enhanced temperature stability of ferroelectric properties in lead-free (1−x)(Bi0.5Na0.4K0.1)TiO3-x(Ba0.5Sr0.5)TiO3 solid solutions

With its complicated composition architecture, (Bi 0.5 Na 0.5 )TiO 3 (BNT)-based relaxor ferroelectrics exhibit distinctive dielectric relaxation phenomena and attractive characteristics. The structural, dielectric, and ferroelectric characteristics of (1– x )(Bi 0.5 Na 0.4 K 0.1 )TiO 3 - x (Ba 0.5 Sr 0.5 )TiO 3 (BNKT- x BST) solid solutions with x = 0–0.4 were thoroughly examined in this study. The x = 0.1 and 0.2 versions exhibited unexpected ferroelectricity enhancement, and the depolarization temperatures and ferroelectric-relaxor transition temperature were both increased compared to that of the BNKT undoped sample. This enhancement is due to the creation of a tetragonal ferroelectric phase after the introduction of a moderate BST member, according to room temperature and temperature-dependent x-ray diffraction data. The characterization of ferroelectric properties indicated that ferroelectricity was enhanced by increasing the rapidly declining temperatures for the remnant polarization and coercive field, compared to those of the BNKT undoped sample. This discovery contributes to a better understanding of the relationship between the structure and properties of complex relaxor ferroelectrics. A phase diagram of the BNKT- x BST solid solution is also provided, which can be used to guide the search for specific lead-free functional materials for the capacitors, actuators, and transducers based on this eco-friendly system.

Investigation of structural, dielectric, impedance and leakage current behaviour of green phase of yttrium barium copper oxide:Y2BaCuO5

Comprehensive study of structural, dielectric, electrical, and ferroelectric characteristics of Yttrium Barium Copper Oxide (Y2BaCuO5) ceramic, (accompanying phase of high-Tc superconductor YBa2Cu3O7-X can unravel plethora of fascinating applications. Y2BaCuO5 green phase cuprate has been prepared by employing ceramic fabrication technology. Room-temperature X-ray diffraction data of the polycrystalline sample suggests that it crystallizes in orthorhombic system in non-centrosymmetric Pbn21 spacegroup. The microstructure and elemental composition clearly illustrated by SEM micrograph and EDAX data. Frequency dependence of dielectric parameter has been discussed using Maxwell-Wagner model. Grain and grain boundary effects discussed using Nyquist plots; fitted to RQC and RC-RQC circuits. Temperature and Frequency dependent conductivity behaviour are explained using Arhenius equation and Jonscher power law. NSPT and CBH model of charge transport mechanisms observed. (I–V) charecteristics demonstrates semiconductor behaviour of Y2BaCuO5 and its suitability for rectifier applications. Existence of hysteresis loop at room and high temperature up to 200 °C suggests ferroelectricity in Y2BaCuO5.

Structural, dielectric, electrical and optical properties of Li/Fe modified barium tungstate double perovskite for electronic devices

In this communication, the synthesis (solid-state reaction route) and characterization (structural and electrical properties) of Li/Fe modified barium tungstate BaWO4 of chemical formula (BaLi)(FeW)O6 double perovskite have been reported. Analysis of room temperature X-ray diffraction data shows the formation of a new single-phase (double perovskite) of tetragonal symmetry. The calculated average crystallite size and lattice strains are found to be 42 nm and 0.111% respectively. The scanning electron micrograph shows that grains are distributed uniformly with less porosity in the material. Detailed studies of field (frequency) and thermal (temperature) dependence of capacitive (dielectric) and resistive (impedance and conductivity) characteristics of the prepared material have shown the dielectric dispersion, relaxation, and non-Debye type of conduction mechanism respectively of the material. The existence of a non-Debye type of relaxation process and thermally activated relaxation process in the material has been analyzed by using impedance spectroscopy and conductivity techniques respectively. The presence of the depressed semicircular arcs in both Nyquist and Cole-Cole plots confirms the semiconductor nature of the material, which is well supported from ZSIMPWIN fitted impedance data. Study of room temperature Raman spectra supports the incorporation of Li/Fe of LiFeO2 in BaWO4 to produce new double perovskite of a composition BaLiFeWO6 of tetragonal symmetry. Further, as the temperature dependence of resistance shows a good stability factor, sensitivity factor, and thermistor constant, the material may be useful for thermistor-related devices. The nature of I–V characteristics confirms the presence of the Ohmic type of conductivity of the material. The energy bandgap of 2.85 eV, obtained from the UV–visible spectrum, suggests the material may also be used for optoelectronic devices.

Structural, microstructural and electrical characteristics of Ca, Sn and Se modified Bi0.5Na0.5TiO3 ferroelectric ceramics

In this paper, studies of structural, microstructural and electrical properties of calcium, tin, and selenium modified bismuth sodium titanate (Bi0.5Na0.5TiO3) compound with a general chemical formula (Bi0.45Na0.45Ca0.1) (Ti0.9Sn0.05 Se0.05) O3, synthesized by a high-temperature mixed oxide reaction method, have been discussed. Analysis of room temperature X-ray diffraction data confirms the formation of perovskite single-phase compound with rhombohedral symmetry. The surface morphology of the sample exhibits the uniform distribution of grains of varying size. Studies of the electrical parameters (dielectric, impedance and conductivity) of the material, collected at various temperatures (75–375 °C) in a wide frequency range (1 kHz–1MHz) have provided its conduction and relaxation behavior. The electric field dependent current density (J-E) characteristics suggest the Ohmic behavior while the field dependent polarization (P-E loop) confirms the ferroelectric nature of the studied material.

Structural and Electrical Performance of (Bi1/2Ba1/4Sr1/4)(Ti1/2Fe1/2)O3Relaxor

The polycrystalline sample of a ternary system of 0.5BF-0.25ST-0.25BT (i.e., Bi0.5Ba0.25Sr0.25)(Ti0.5Fe0.5)O3 was prepared via a conventional high-temperature solid-state reaction technique. The preliminary structural analysis using room temperature X-ray diffraction (XRD) data shows the tetragonal as well as pseudo-cubic nature of the compound. Analysis of temperature and frequency-dependent dielectric parameters, obtained in a wide range of temperature and frequency, exhibits diffused phase transition with relaxor-ferroelectric nature of the material. This observation has been confirmed through temperature and frequency evolved P-E loops. The sample is free from impurities and is structurally stable. The Vogel-Fulcher plot was used to confirm the relaxor type of ferroelectric behavior of the material. The dielectric relaxation, grain, grain-boundary contribution, and semiconductor (negative temperature coefficient of resistance) nature of the compound have been analysed through impedance analysis. The current-voltage (I-V) and leakage characteristics confirm the bulk limited (SCLC) and interface limited (Schottky, Poole-Frankel emitted and Fowler-Nordheim type) conduction mechanisms. The energy bandgap, calculated from the I-V-spectra, is found to be 0.93 eV in the particular (high) temperature range indicating the semiconducting nature of the material.

Investigation on diffuse phase transition through Raman and dielectric properties of Pb(Fe0.5Nb0.5)O3 – Pb(Co0.33Nb0.67)O3 solid solutions

We report a series of Pb based multiferroic solid solutions (1-x) Pb(Fe0.5Nb0.5)O3 – (x) Pb(Co0.33Nb0.67)O3 (0.1 ≤ x ≤ 0.5) (shortened as PFCN), synthesized using a single-step solid-state reaction method. The structural, microstructural, Raman, and temperature (301–481 K) dependent dielectric (102–106 Hz) and conductivity properties were thoroughly investigated. The room temperature X-ray diffraction data reveals the monoclinic phase with the Cm space group for all the solid solutions. The atomic-level structural parameters were obtained for all the solid solutions from the Rietveld refinement technique, and it was observed that an increase in the unit cell volume with an increase of PCN content in PFN. The field emission scanning electron microscope images confirm the densely packed, uniform coarse arrangement in all the samples. In x = 0.4 and 0.5, a small amount of porous structure was noticed, indicates the reduction in the densities. Energy-dispersive X-ray spectroscopy reveals the existence of Pb, Fe, Co, Nb, and O elements according to stoichiometry. The temperature-dependent Raman spectra of all the solid solutions show a decrease in the intensity and changes in the spectral line shape of B-localized F1u (~250 cm−1) and BO6 octahedral rotation F1g (~260 cm−1) modes around the characteristic temperature, may be a structural transformation from monoclinic to cubic above Tm. The frequency-dependent ε′ and tanδ reveal the presence of Maxwell-Wagner polarization in the lower frequency. The temperature-dependent ε′ shows the ferroelectric relaxor type diffused phase transition Tm (TC) around ~360 K, ~340 K, ~330 K & ~320 K for x = 0.1, 0.2, 0.3 and 0.4, respectively. The reported Tm (TC) systematically decreases with increasing x due to the lower Tm (TC) of PCN compared to PFN. These results were consistent with the anomalies observed at the vicinity of Tm in the Raman spectra. The frequency-dependent ac-conductivity studies reveal the negative temperature coefficient of resistance behavior and obey Johnscher's power law. For x = 0.1 to 0.4, the hump-like behavior was found in both temperature-dependent tanδ and ac conductivity around the transition temperature related to the reorientation of domains, domain wall motion, dipolar contribution to the ferroelectric materials.

Study of Structural, Magnetic, and Mossbauer Properties of Dy2Fe16Ga1−xNbx (0.0 ≤ x ≤ 1.0) Prepared via Arc Melting Process

Intermetallic compounds of Dy2Fe16Ga1−xNbx (x = 0.0 to 1.00) were synthesized by arc melting. Samples were investigated for structural, magnetic, and hyperfine properties using X-ray diffraction, vibration sample magnetometer, and Mossbauer spectrometer, respectively. The Rietveld analysis of room temperature X-ray diffraction data shows that all the samples were crystallized in Th2Fe17 structure. The unit cell volume of alloys increased linearly with an increase in Nb content. The maximum Curie temperature Tc ~523 K for x = 0.6 sample is higher than Tc = 153 K of Dy2Fe17. The saturation magnetization decreased linearly with increasing Nb content from 61.57 emu/g for x = 0.0 to 42.46 emu/g for x = 1.0. The Mössbauer spectra and Rietveld analysis showed a small amount of DyFe3 and NbFe2 secondary phases at x = 1.0. The hyperfine field of Dy2Fe16Ga1−xNbx decreased while the isomer shift values increased with the Nb content. The observed increase in isomer shift may have resulted from the decrease in s electron density due to the unit cell volume expansion. The substantial increase in Tc of thus prepared intermetallic compounds is expected to have implications in magnets used for high-temperature applications.

Effect of substitution of La3+ on structural and electrical properties of Sr(Fe0.5Nb0.5)O3 ceramic

In this work, we have mainly reported the effect of lanthanum substitution on structural, dielectric, impedance and transport properties of strontium iron niobate (i.e., Sr1-xLax(Fe0.5Nb0.5)1-x/4O3 (x = 0, 0.05, 0.1, 0.15, 0.2)). The materials were synthesized using standard ceramic technology. The preliminary structural analysis was done by using the room temperature X-ray diffraction data. The samples of higher concentrations (x = 0.15 and x = 0.20) show the development of an additional phase (i.e., LaNbO4 and Sr3La4O9). Studies of frequency and temperature dependence of dielectric parameters exhibit an anomaly and relaxor behavior in the compounds. The electrical impedance and modulus analysis of frequency and temperature-dependent data show the contributions of grains and grain boundaries in the resistive and capacitive properties of the compounds. The study of transport properties of AC conductivity has provided the conduction and relaxation mechanism. The substitution of La3+ has significantly changed the dielectric constant, tangent loss, and transport properties of the material.

Studies of structural, dielectric and impedance spectroscopy of Ca/Zr modified BiFeO3 ceramics

In this communication, the structural and electrical (dielectric, polarization, impedence, and conductivity) properties of the polycrystalline samples of Ca/Zr modified BiFeO3 samples with chemical formula (Bi1-xCax) (Fe1-xZrx)O3; x = 0.05, 0.1, 0.15, 0.20 were prepared using a solid-state reaction method at 800 °C have been reported. The analysis of room temperature X-ray diffraction data of above-synthesized electro-ceramics confirms the formation of single phase perovskite in rhombohedral phase. The scanning electron microscope photographs provide the micro-structural study of the samples. The existence of ferroelectricity in the materials was studied by the variation of electric polarization with the applied electric field. Many important results have been obtained from the dielectric and impedance studies of the samples at a varying frequency (1 kHz–1000 kHz) and temperature (250C–300 °C). The contribution of both grains and grain boundaries towards the total resistance and capacitance of the four compounds is found from the Nyquist plots. From the conductivity study, the dielectric properties and conductivity of the materials were obtained. The J–E characteristics of the samples provide the Ohmic behavior with slope closer to 1.

Structural, dielectric, electrical and magnetic properties of chemicothermally synthesized material: BiCaFeCeO6

In this communication, detailed studies of structural, micro-structural, dielectric, electrical (impedance, modulus and conductivity) and magneto-electric characteristics of a chemico-thermally synthesized sample of a double perovskite bismuth calcium iron cerate (BiCaFeCeO6) have been reported. Preliminary structural analysis of room temperature X-ray diffraction data shows orthorhombic structure of the material. The homogeneous distribution of the grains of different dimensions (shape, size, etc) with a small number of voids observed in the scanning electron micrograph suggests the formation of high-density sample. Detailed analysis of dielectric and impedance experimental data, collected at different frequency and temperatures, have provided many important characteristics of the material, such as (a) grains, grain boundaries, and electrode dependent capacitive and impedance parameters, (b) co-relation between the structure, micro-structure and physical properties and (c) the relaxation characteristics of the tested samples. The nature of frequency dependence of AC conductivity of the material obeys the Jonscher's universal power law. The temperature dependence of conductivity provides the conduction mechanism in the material. Detailed studies of field dependence of electric polarization, magnetization and magneto-electric coefficient at room temperature exhibit the multiferroic characteristics of the material.

The caesium phosphates Cs3(H1.5PO4)2(H2O)2, Cs3(H1.5PO4)2, Cs4P2O7(H2O)4, and CsPO3

The caesium phosphates Cs3(H1.5PO4)2(H2O)2 and Cs3(H1.5PO4)2 were obtained from aqueous solutions, and Cs4P2O7(H2O)4 and CsPO3 from solid state reactions, respectively. Cs3(H1.5PO4)2, Cs4P2O7(H2O)4, and CsPO3 were fully structurally characterized for the first time on basis of single-crystal X-ray diffraction data recorded at − 173 °C. Monoclinic Cs3(H1.5PO4)2 (Z = 2, C2/m) represents a new structure type and comprises hydrogen phosphate groups involved in the formation of a strong non-symmetrical hydrogen bond (accompanied by a disordered H atom over a twofold rotation axis) and a very strong symmetric hydrogen bond (with the H atom situated on an inversion centre) with symmetry-related neighbouring anions. Triclinic Cs4P2O7(H2O)4 (Z = 2, Pbar{1}) crystallizes also in a new structure type and is represented by a diphosphate group with a P–O–P bridging angle of 128.5°. Although H atoms of the water molecules were not modelled, O···O distances point to hydrogen bonds of medium strengths in the crystal structure. CsPO3 is monoclinic (Z = 4, P21/n) and belongs to the family of catena-polyphosphates (MPO3)n with a repetition period of 2. It is isotypic with the room-temperature modification of RbPO3. The crystal structure of Cs3(H1.5PO4)2(H2O)2 was re-evaluated on the basis of single-crystal X-ray diffraction data at − 173 °C, revealing that two adjacent hydrogen phosphate anions are connected by a very strong and non-symmetrical hydrogen bond, in contrast to the previously described symmetrical bonding situation derived from room temperature X-ray diffraction data. In the four title crystal structures, coordination numbers of the caesium cations range from 7 to 12.Graphic abstract

Combine effect of BaSnO3 and BaSeO3 substitution on structural and electrical properties of Bi0·5K0·5TiO3 ceramics

In this research article, structural (crystal structure, micro structure) and electrical (dielectric, impedance and conductivity) properties of BaSnO3 (BSn) and BaSeO3 (BSe) modified (Bi0·5K0.5) TiO3 ceramic (i.e., (1–2x)((Bi0·5K0.5)TiO3)+xBaSnO3+xBaSeO3 with x = 0, 0.05, 0.10, 0.15 (BKT-BSn-BSe) have been fabricated via a high-temperature cost effective mixed oxide reaction process. The structural, micro structural and electrical characteristics of the parent compound ((Bi0·5K0.5) TiO3) have significantly been influenced by the substitution of BSn–BSe (in equal ratio) in it over a high temperature (100–500 °C) and frequency (1 kHz–1 MHz) range. Structural analysis of the compounds, carried out by the room temperature X-ray diffraction (XRD) data, confirms the formation of single phase compounds with tetragonal structure. The surface morphology of the materials, exhibits the homogeneous distribution of grains (with few voids) throughout the surface of the materials. The presence of bulk and grain boundary effect of the material is confirmed by the nature of Nyquist plot. J-E characteristics of the compounds show a negative temperature co-efficient of resistance (NTCR) behavior in them, similar to that of a semi-conductor. The ferroelectric phenomena of the prepared materials are studied by field dependence of polarization (PE) hysteresis loop study.

Structural, Electrical, and Magnetic Characteristics of Chemically Synthesized Lead-Free Double Perovskite: BiMgFeCeO6

In the present paper, structural, microstructural, dielectric, electrical, and magnetic characteristics of a chemically synthesized double perovskite compound BiMgFeCeO6 have been reported. An analysis of room temperature X-ray diffraction data has shown formation of compound with orthorhombic symmetry. Study of micrographs of the pellets has shown the homogeneous distribution of grains, grain boundaries, and presence of required elements in the sample. Detailed studies of dielectric (er, tan δ) and impedance parameters of the material have provided an insight into the electrical properties and understanding of types of relaxation process occurred in the material. The semiconductor characteristic (i.e., negative temperature coefficient of resistance behavior) of the compound at high temperature has been observed in the temperature-dependent dc conductivity study. As the characteristics of the frequency dependence of ac conductivity of the material follow Jonscher’s universal power law, the validity of analysis and good quality of the sample are confirmed. The occurrence of ferroelectric polarization (hysteresis loop), magnetization loop, and magnetoelectric pattern in the material confirms the multiferroicity in it.

Structural, dielectric, and electrical characteristics of selenium-modified BiFeO3–(BaSr)TiO3 ceramics

The selenium (Se)-modified 0.5BiFeO3–0.5(BaSr)TiO3 was synthesized employing a high-temperature solid-state technique. Structural analysis (through Rietveld refinement) of the room-temperature X-ray diffraction pattern and data of the material confirms the tetragonal (P4mm) symmetry of the compound. Studies of scanning electron micrograph (SEM) and energy dispersive X-ray spectroscopy (EDS) data reveal the nature and characteristics (i.e., size, shape and distribution of grains, grain boundaries, voids and presence of elements, etc.,) of surface morphology and structure of the compound. Detailed analysis of temperature and frequency dependence of dielectric and impedance data exhibits the relaxor type of ferroelectric behavior and semiconductor (negative temperature coefficient of resistance) nature of the material. The material is found to have high resistivity and low dielectric (tangent) loss. Study of the temperature dependence of leakage current characteristics (i.e., electric field dependent current density) shows the leaky behavior of the material. The Se-modified 0.5BiFeO3–0.5(BaSr)TiO3 (BFBST), compared to its components (BFBST and pure BiFeO3), material possesses different types of conduction process, like space charge limited (SCLC), Ohmic, Hopping type. Poole–Frenkel emission (PFE) and Schottky emission (SE) fitted data give an evidence/idea about the bulk-limited and interface-limited conduction mechanism present in the system. The energy gap values (Eg) of Se substituted BFBST and BiFeO3 are found to be 0.55 eV and 0.78 eV, respectively, in the low-temperature range.

Structural, dielectric and electrical characteristics of lead-free scandium modified barium iron niobate: Ba(Fe0.5-x ScxNb0.5)O3

Scandium (Sc) modified barium iron niobates (i.e., Ba(Fe0.5-x ScxNb0.5)O3 (x = 0.03,0.05 and 0.07) (BFSN)) were synthesized by using a standard ceramic technology (i.e., high-temperature solid-state reaction of mixed oxide route). The analysis of room temperature X-ray diffraction data shows the monoclinic phase of the materials. The dielectric and impedance parameters were measured in different temperature (250C–500 °C) and frequency (1 kHz-1 MHz) ranges. Detailed study of temperature dependent dielectric constant shows the two anomalies; one may be related to the ferroelectric to paraelectric phase transition at about 249 °C and another at about 368 °C may be due to some extrinsic effects (due to creation of oxygen vacancies for variable oxidation states). The grains and grain boundary contributions in resistive and capacitive characteristics, temperature activated polarization mechanisms are analysed. The Leakage (J ~ E) characteristics illuminate the bulk (ohms due to hopping of charge carriers and, space charge limited) conduction processes of the samples. With the increase in scandium, diffusivity decreases in BFSN compounds.