Room Temperature X-ray Diffraction Research Articles

Influence of vanadium substitution on dielectric and electrical characteristics of NaNbO3 ceramics in polymorphic R and S phase

The lead-free polycrystalline NaNb1−xVxO3 (NV: 0.00 ≤ x ≤ 0.06) samples are prepared by standard solid-state reaction technique. Room temperature X-ray diffraction (XRD) analysis suggests an orthorhombic crystal structure for NV ceramics. Field emission scanning electron microscopy (FE-SEM) shows distinguishable regular-shaped grains with clear grain boundaries. The dielectric and electrical properties of NV ceramics are investigated in the polymorphic R and S- orthorhombic phase. The structural transitions due to change in crystal symmetry is analyzed from the dielectric measurement and accompanied by dielectric anomaly at around 400 ∘C in temperature dependent dielectric characteristics. All the frequency dependent dielectric and electric properties are analyzed above the transition temperature i.e. in 400–520 ∘C (R and S polymorphic phase). The existence of typical negative temperature coefficient resistance (NTCR) behavior confirms by complex impedance study. The detailed investigation of Nyquist plots suggest that grain-resistance (Rg) and grain-boundary resistance (Rgb) are strongly affected by both the applied temperature and V-content in the samples.

Room temperature ferromagnetism in Zn-doped NiO nanoparticles: An experimental and DFT+U approach

Abstract We report the room temperature ferromagnetism in Zn-doped NiO nanoparticles of Ni1−x ZnxO (x = 0.00, 0.01, 0.03, 0.05 and 0.1) prepared by the sol-gel method. Zn dopant has significant influence on structural, optical, and magnetic properties of NiO crystal when there is a size reduction and lattice distortions. The crystalline nature of the samples were characterized by the room temperature X-ray Diffraction and we found that the range of crystallite size is about 7 ± 0.01 to 9 ± 0.01 nm for 3–10% of Zn doping concentration. The lattice parameter and the effective strain increases with the increase of doping concentration. Local structure and defects are probed through Raman characterization which reveals that there are no secondary or impurity peaks on the Zn-doped NiO samples. Photoluminescence spectra at room temperature shows two major emission peaks at wavelength 357 nm and 393 nm for both pure and Zn-doped NiO powder respectively. There also exists a blue shift for wavelength 357 nm emission band with the increase of Zn doping concentration. The band gap energy calculated from the PL spectra is ≈3.46 eV for pure NiO and it increases with the doping upto 3% then it decreases with further doping. To understand the effect of doping on magnetic properties, we measured the temperature dependent M-H loops and M-T curve for zero field cooled (ZFC) and field cooled (FC) condition in the temperature range 25–350 K using Vibrating Sample Magnetometer. We observed that the Ni1−x ZnxO nanoparticles are ferromagnetic in nature at room temperature with highest magnetic moment of ≈1.9 emu/g when the doping of Zn is 3% and it decreases with further increase of doping concentration. M-T data bifurcation peak was observed around 300 K and a broad peak in ZFC curve below the bifurcation. This broad peak is attributed to the thermal relaxation of uncompensated spins. We have also investigated the first-principle DFT+U calculation to study the electronic properties of the materials. The results show that the Zn-doped NiO with oxygen vacancies are ferromagnetic in nature whereas without defects the compound is non-magnetic, which agrees quite well with the experimental results. The nanoparticle with ferro-magnetic properties have potential application in the field of nanomagnetism and also its optical properties could be useful for optical device applications.

Effect of Fe and Co doping on structural and electrical properties of La0.5Sr1.5MnO4 layered-structure and the corresponding La0.5Sr0.5MnO3 perovskite

In this study, structural and electrical properties of La0.5Sr1.5Mn0.5T0.5O4 (T = Mn, Fe, and Co) manganites, with K2NiF4 structure, have been investigated and compared with those of La0.5Sr0.5Mn0.5T0.5O3 perovskite manganites. The room temperature X-ray diffraction patterns of the synthesized La0.5Sr1.5Mn0.5T0.5O4 layered-structures and La0.5Sr0.5Mn0.5T0.5O3 perovskites were indexed with tetragonal and orthorhombic structures, respectively. The FE-SEM images revealed that the average size of La0.5Sr1.5Mn0.5T0.5O4 particles prepared by solid state reaction method using La0.5Sr0.5Mn0.5T0.5O3, as the starting materials, is larger compared with that of La0.5Sr0.5Mn0.5T0.5O3 synthesized by the modified sol-gel route. The SEM micrographs of the sintered ceramics indicated that the average grain size of La0.5Sr1.5Mn0.5T0.5O4 layered-structures is larger than that of the corresponding La0.5Sr0.5Mn0.5T0.5O3 perovskites, which is supported by FE-SEM images. The electrical conductivity measurements, in the range of room temperature to 800 °C, indicated that these oxides have semiconducting behavior, and their transport properties can be described by small polaron conduction mechanism. Results showed that La0.5Sr1.5Mn0.5T0.5O4 layered-structures have lower electrical conductivity in comparing to the corresponding La0.5Sr0.5Mn0.5T0.5O3 perovskites, since the perovskite structure provides three-dimensional (Mn/T)3+–O–(Mn/T)4+ interaction, whereas it is two-dimensional interaction in the layered-structure. The reduction in conductivity with Fe doping could be due to the presence of Fe3+ ions, which causes a decrease in Mn3+/Mn4+ ratio and the number of electrons involved in hopping mechanism. The electrical conductivity enhancement of La0.5Sr1.5MnO4 by doping Co can be associated with reducing Mn/Co‒O bond length and the increase in the overlap between O 2p and Mn/Co 3d orbitals.

Structural, magnetic, dielectric and hyperfine interaction studies of titanium (Ti4+)-substituted nickel ferrite (Ni1+xTixFe2−2xO4) nanoparticles

Tetravalent titanium (Ti4+)-substituted nickel ferrite nanoparticles with varying composition were prepared by standard sol–gel auto-combustion method. The phase identification and nanocrystalline nature were studied through X-ray diffraction (XRD) technique. The room temperature X-ray diffraction pattern show only those planes which belong to cubic spinel structure. No extra peak other than cubic spinel structure appeared in the XRD pattern suggesting that the prepared nanoparticles possess single-phase cubic spinel structure except x = 0.4, 0.5 and 0.6. The plane (311) observed in the XRD pattern showed maximum intensity and is used to calculate the crystallite size (t). The Debye–Scherrer’s formula was used to calculate the crystallite size which was found to vary between 19 and 23 nm for varying Ti composition x. The lattice constant (a) and other structural parameters were obtained from XRD data. The lattice constant is found to be decreasesing with increase in Ti substitution. The FE-SEM images of typical samples confirmed the spherical shape morphology. The magnetic properties were studied by means of vibrating sample magnetometer and Mossbauer spectroscopy technique. All the samples exhibit a good magnetic property which decreases with Ti substitution. The saturation magnetization goes on decreasing from 43.14 (for x = 0.0) to 12.86 (for x = 0.5) which may be attributed to the decreasing A–B interaction. The Mossbauer spectrum of typical samples show sextet pattern. The Moosabauer parameters like isomer shift, quadrupole splitting, Line width etc. were obtained. The dielectric parameters such as dielectric constant, dielectric loss and dielectric loss tangent etc. were recorded using vector network analyzer.

Structural and Electrochemical Properties of Lanthanum Silicate Apatites La10Si6−x−0.2AlxZn0.2O27−δ for Solid Oxide Fuel Cells (SOFCs)

An excellent oxide ion conductivity with high oxygen transportation of lanthanum silicate apatite at the solid oxide fuel cell (SOFC) can be achieved through the solid-state reaction method. The doped La10Si6−x−0.2AlxZn0.2O27−δ (x = 0.2 and 0.4) materials sintered at 1600°C accomplished crystallinity and crystal structure of apatite-type. The structural and electrochemical characterizations of La10Si6−x−0.2AlxZn0.2O27−δ (x = 0.2 and 0.4) were executed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and electrochemical impedance spectroscopy (EIS) measurements. The total oxide ion conductivities of La10Si6−x−0.2AlxZn0.2O27−δ (x = 0.2 and 0.4) were measured from low to intermediate operating temperature range (450 to 800°C) using electrochemical impedance spectroscopy. Room temperature XRD patterns of La10Si6−x−0.2AlxZn0.2O27−δ (x = 0.2 and 0.4) exhibited La10Si6O27 apatite phase with space group P63/m as the main phase with the minor appearance of La2SiO5 as an impurity phase. The highest total oxide ion conductivity of 3.24 × 10−3 Scm−1 and corresponding activation energy of 0.30 eV at 800°C were obtained for La10Si5.6Al0.2Zn0.2O26.7 which contains a low concentration of Al3+ dopant.

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.

Cobalt-free perovskite Ba1-xNdxFeO3-δ air electrode materials for reversible solid oxide cells

We report on Ba1-xNdxFeO3-δ, a cobalt-free perovskite material, with a view to its use as a next-generation air electrode material in reversible solid oxide cells (RSOCs). BaFeO3-δ (BFO) has long been considered a potential candidate cathode material due to its high oxygen vacancy concentration and electrical conductivity; however, it is difficult to synthesize in a single phase. To overcome this problem, Nd3+ is doped into Ba-sites to reduce impurity phases and create a single perovskite phase. In-situ high temperature and room temperature X-ray diffraction analyses are carried out to investigate Nd3+-doped BFO. We find that Ba0.97Nd0.03FeO3-δ shows the highest electronic conductivity and lowest TEC value among the various doping concentrations tested, making this material most suitable for application in RSOCs. In addition, the polarization resistance of Ba0.97Nd0.03FeO3-δ has the lowest value in yttria-stabilized zirconia symmetric cells. To determine the reasons for the high catalytic activity of Ba0.97Nd0.03FeO3-δ, X-ray photoelectron spectroscopy and iodometric titration are carried out, the results demonstrate that the lower doping concentration of Nd3+ results in an advantage in terms of the number of additional oxygen vacancies created. Moreover, electrical conductivity relaxation measurements show that the Ba0.97Nd0.03FeO3-δ has a fast bulk diffusion coefficient and fast surface exchange coefficient. Hence, the solid oxide fuel cell and electrolysis mode performances when using Ba0.97Nd0.03FeO3-δ are excellent and a high power output of 1.2 W cm−2 at 800 °C can be achieved.

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.

Evaluation of irradiation effects on the microstructure and properties of Ag-sheathed Bi-2212 superconducting round wire for future application in CFETR

The Chinese Fusion Engineering Test Reactor (CFETR) is designed to build a fusion engineering Tokamak reactor generating fusion power of 200–1500 MW, and to test the breeding tritium during fusion reaction. This may require a maximum magnetic field up to 15 T in the central solenoid and toroidal field coils. New superconducting materials should be developed for satisfying the next-generation fusion reactors with critical requirements. Recently, Bi2Sr2CaCu2Ox (denoted as Bi-2212) is considered as one of the most promising potential superconductors to be used as the magnets in CFETR, however, they will be subjected to harsh irradiation under operating conditions. The irradiation effects of the high-energy helium ions on the Ag-sheathed Bi-2212 superconducting round wire have been explored for the first time in this work. The microstructure and the critical current at 4.2 K of the superconducting wire before and after irradiation have been carefully investigated. Room-temperature x-ray diffraction (XRD) profiles showed that all the peaks shifted rightward significantly with a broadened (111)Ag peak, indicating that the high-energy He+ irradiation resulted in appreciable defects and strain in the superconducting wire. Meanwhile, the in-situ high-temperature XRD tests showed that the lattice constant and the thermal expansion coefficient were deduced in the irradiated sample to be due to the presence of the generated defects. After irradiation, the grain size of the Ag sheath was refined, and the lattice of Bi-2212 superconductor was distorted obviously, as confirmed by transmission electronic microscopy. The critical current IC at 4.2 K of the superconducting wires in the field of 0–12T determined by the four-probe technique, decreased substantially after irradiation because of the lattice distortion and the consequently induced strain in the Bi-2212 superconductor. This work provides a solid basis for evaluating and understanding the irradiation effects upon the Ag-sheathed Bi-2212 superconducting wire, more promising for future application in CFETR.

Low temperature synthesis and investigations of magnetic properties of cobalt ferrite nanoparticles

In the present study we report the synthesis of cobalt ferrite nanoparticles using one of the well-known wet chemical method i.e. sol-gel auto combustion technique. The synthesis was carried out at sufficiently low temperature of 100°C. Citric acid was used as a fuel in the synthesis process. The obtained nanoparticles were sintered at 550°C for 4 h and then used for structural and magnetic investigations. The phase pure nature and nano crystalline nature was investigated through X-ray diffraction technique. Room temperature X-ray diffraction pattern show well defined reflections oriented at different Bragg’s angle corresponding to Miller indices (220), (311), (222), (400), (422), (511) and (440). All this reflections belongs to cubic spinel structure. Thus, XRD analysis confirms the formation of single phase compound. The particle size was obtained through Scherrer’s equation and found to be 21 nm, indicating the nanocrystalline nature. The magnetic properties were investigated using pulse field hysteresis loop tracer at room temperature. The saturation magnetization show increased values as compared to the bulk cobalt ferrite. The coercivity found to be less which exhibits the superparamagnetic behaviour. The obtained structural and magnetic parameters are useful in biomedical applications.

Influence of non-magnetic Zn-doping on the structural and the magnetic properties of magnesium ferrite

Spinel ferrites are the important class of soft magnetic material and are of interest to many researchers due to their excellent electrical and magnetic properties. Magnesium ferrite (MgFe2O4) is one such spinel ferrite with great potential technological applications. In the present study, the magnesium ferrite (Mg0.8Zn0.2Fe2O4) samples were prepared by well-known sol-gel auto-combustion method. The influence of Zn-doping on the structural and magnetic properties was investigated by X-ray diffraction and magnetization studies. The room temperature X-ray diffraction studies of the pure MgFe2O4 and Zn-doped Mg-Fe2O4 (Mg0.8Zn0.2Fe2O4) revealed the formation of single phase cubic spinel structure. The crystallite size obtained from Sherrer’s formula indicated that the Zn-doped and undoped shows nanocrystalline nature with crystallite size 22 nm and 24 nm respectively. The lattice constant (?) was found to be increased after Zn doping. Several other structural parameters are also increased after Zn doping. The magnetic properties were investigated by means of pulse field hysteresis loop technic. The M-H plot exhibits typical ferrimegnetic nature. The saturaturation magnetization increases after Zn doping. The observed magnetic behaviour of Mg0.8Zn0.2Fe2O4 nanocrystalline ferrite was on the basis of theoretical model.

Magnetic Properties of Nickel Ferrite Magnetic Nanoparticles Prepared via Glycine Assisted Sol-Gel Auto Combustion Route

The present research paper deals on the synthesis of nickel ferrite (NiFe2O4) nanoparticles using sol-gel auto combustion technique in which glycine was used a chelating agent. The prepared nanoparticles were annealed at 500°C for 4 h. and then used for structural, magnetic and other investigations. The X-ray diffraction technique was used for phase purity and structural determination. Room temperature X-ray diffraction pattern of NiFe2O4 nanoparticles shows all the reflections belonging to cubic spinel structure. The reflections are intense and slightly broader. No extra peak other than cubic spinel structure was observed in the XRD pattern. This indicates the single phase formations of the nickel ferrite nanoparticle. The refinement of XRD data has been carried out by using full proof programmer. The lattice constant was calculated using XRD data as well as Cohen’s least square method, the obtained lattice constant matches with the reported value. The other structural parameters like lattice strain, X-ray density etc. structural parameters were also calculated using standard relations. The crystallite size was determined using Scherrer’s formula in which the most intense peak (311) was considered. The crystallite size was found to be 24 nm which indicates the nanocrystalline nature of the prepared nickel ferrite nanoparticles. The magnetic properties of were investigated using the pulse field hysteresis loop (PFHL) technique at room temperature. The saturation magnetization, coercivity and remanence magnetization shows enhanced values. All the structural and magnetic properties results were compared with the reported data in which other chelating agent like citric acid etc.

Rare Earth Ion (La3+) Doped BaTiO3 Perovskite Nanoceramics for Spintronic Applications

The present study reports the structural and morphological investigation of La3+ doped BaTiO3 nanoceramics prepared by combustion synthesis. The effect of La3+ doping on the structural and morphological properties was examined by the X-Ray diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) technique. Room temperature XRD analysis shows that prepared samples are in a single phase with the tetragonal structure. Structural parameters like average crystallite size (D) and lattice constant (a and c) were calculated from the XRD data. The surface morphology of the samples was studied by transmission electron microscopy (TEM) technique. It was found that the nanoparticles are in tetragonal shape with agglomeration to the some extent. All the outcomes show that La doped BaTiO3 nanoceramics are promising candidates for spintronic applications.

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

Structural, dielectric, ferroelectric and tuning properties of Pb-free ferroelectric Ba0.9Sr0.1Ti1-xSnxO3

A series of Pb-free ferroelectric materials Ba0.9Sr0.1Ti1-xSnxO3 (BSTS-x) with 0 ≤ x ≤ 0.15 was successfully prepared via solid-state reaction method. The effect of Sn substitution on the crystal structure, microstructure, dielectric behavior, ferroelectric and tunable features of BSTS-x ceramics were systematically investigated. Room temperature (RT) x-ray diffraction (XRD) analysis using the Rietveld refinement method reveals that all the synthesized BSTS-x ceramics were well crystallized into single perovskite structure. The results show a tetragonal phase for 0.00 ≤ x ≤ 0.02, which evolves to orthorhombic and tetragonal coexisting phases for 0.05 ≤ x ≤ 0.07. The composition x = 0.10 showed a mixture of tetragonal, orthorhombic and rhombohedral phases at RT, while a single cubic phase is observed for x = 0.15. The crystal phases determined by XRD were confirmed by Raman spectroscopy. Enhanced dielectric permittivity with a maximum value of ε'~35000 is observed for x = 0.10 at RT. The ferroelectric behavior of BSTS-x ceramics was investigated through polarization hysteresis loops and tunability measurements. High tunability of 63% at RT and under the low DC-applied electric field of 1.40 kV/cm is achieved for x = 0.10.

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.

Effect of the low constituent boron on martensitic transformation, magnetic, and magnetocaloric properties of Ni50Mn35In15 Heusler alloys

We report the structural, magnetic, and magnetocaloric properties Ni50Mn35−xBxIn15 (x = 1,1.5) Heusler alloys by using room-temperature X-ray diffraction (XRD), differential scanning calorimetry (DSC), and magnetization measurements. The substitution of B instead of Mn decreases the transition temperatures. Moreover, we observe a large magnetization difference between austenite and martensite phases with a thermal hysteresis around the martensitic transition. Magnetic field dependent measurements reveal that the application of a magnetic field stabilizes the austenite phase, which has higher magnetization. We calculate magnetic entropy change by two methods, namely, Maxwell relation and fraction method. We computed a maximum magnetic entropy change of 15 J kg−1K−1 and 8 J kg−1K−1 around magnetostructural phase transition for a magnetic field change of 5 T, respectively, for Ni50Mn34B1In15 and Ni50Mn33.5B1.5In15 samples.