Standard Solid-state Reaction Method Research Articles

Magneto-electric behaviors of La0.67−xNdxSr0.33MnO3 system

The polycrystalline samples La0.67−x Nd x Sr0.33MnO3 (x = 0.1, 0.2, 0.3, 0.4, 0.5) were prepared by standard solid-state reaction method, and the M–T curves, electron spin resonance (ESR) curves, infrared spectra, Raman spectra, ρ–T curves and MR–T curves of the compounds above were measured. The results show that single phase can be obtained at different Nd substitution ratios, and with the increase in Nd doping, the magnetic structure of the system transforms from long-range ferromagnetic order to spin cluster glass state and antiferromagnetic state; and the phase separation appears in the samples with x = 0.3 and 0.4. The transport property exhibits variation with the increase in Nd doping, and the electric behavior of the sample transforms (from metal state to insulator–metal transition, and then insulator state) is accompanied by colossal magnetoresistance (CMR) effect, which can be attributed to the different couplings of sublattices induced by Nd doping and the interface tunneling effect related to the spin.

Dielectric, impedance and transport characteristics of (Bi0.6Pb0.4Fe0.6Ti0.4)O3

Single-phase polycrystalline sample of (Bi0.6Pb0.4Fe0.6Ti0.4)O3 was synthesized by a standard high-temperature solid-state reaction method. Preliminary structural analysis of the material using room temperature X-rays diffraction data and pattern exhibits its tetragonal structure. Detailed studies of frequency and temperature dependence of dielectric, impedance and transport properties of (Bi0.6Pb0.4Fe0.6Ti0.4)O3 in the wide range of frequency (103–106 Hz) at different temperature (25–500 °C) have provided many interesting results useful for device applications. The frequency dependence of ac conductivity of the material obeys Jonscher’s universal power law. The results obtained on transport properties of the materials have been interpreted in terms of a two-layer model with conducting grains partitioned from each other by poorly conducting grain boundaries. Based on this model, the two electrical responses in impedance and modulus formalisms have been suggested to investigate the effect of grain and grain-boundary.

Structural and magnetic studies on Fe doped zinc oxide, Zn1−x Fe x O synthesized by solid state reaction

High purity Fe2O3 doped ZnO composites were grown by standard solid state reaction method in air at temperature range of 1350 °C for 10 h. The structures of the grown samples were investigated by X-ray diffraction studies. Single phase ZnO was observed indicating substitutional addition Fe2+ ion in Zn lattice. Electron density studies were carried out and sharing of the electrons between the atoms were observed in different planes and directions. Room temperature ferromagnetism can be observed in Fe-doped ZnO using vibrating sample magnetometry showing an increasing trend as the dopant concentration increases. Scanning electron microscopy micrographs along with energy dispersive X-ray analysis were taken to study of structure of the grown composites and to find the presence of Fe in ZnO.

Synthesis and enhancement of multiferroic properties of (x)Ba0.95Sr0.05TiO3–(1−x)BiFe0.90Dy0.10O3 ceramics

Polycrystalline (x)Ba0.95Sr0.05TiO3–(1−x)BiFe0.90Dy0.10O3 [(x)BST–(1−x)BFDO] ceramics were synthesized by the standard solid-state reaction method. Samples prepared from these powders were sintered at various temperatures (900–1000°C). The crystal structure, microstructure, magnetic, dielectric, complex impedance and magnetoelectric properties of the (x)BST–(1−x)BFDO ceramics were systematically investigated. The X-ray diffraction pattern indicated that (x)BST–(1−x)BFDO ceramics showed a structural transition from rhombohedral to cubic phase. The average grain size increased to a maximum 2.86μm for x=0.20 and then decreased. M–H plot showed weak ferromagnetism for x=0.00 to 0.30. The magnetization value increased for increasing BST substitution up to x=0.20 due to the modification of crystal structure and then decreased for further increasing due to the nonmagnetic behavior of BST. A significant remnant magnetization (0.086emu/g) and a coercive magnetic field (103.62Oe) were also obtained for this solid solution. The complex initial permeability increased with the increase of both BST content (up to x=0.20) and sintering temperatures. The room-temperature dielectric constant increased whereas dielectric loss decreased with increasing BST content because of reducing oxygen vacancies. Impedance spectroscopy analysis confirmed the conducting grains and highly resistive grain boundaries affecting the conductivity but the grains had major contribution in the conduction mechanism. Magnetoelectric voltage coefficient (αME) increased with the increase of BST content because of strong interaction between magnetic and ferroelectric domains. The highest value of αME=1.67mVcm−1Oe−1 was observed for x=0.20 solid solution sintered at Ts=1000°C because of uniform grains in size and shape at this composition.

Magnetoelectric properties in bulk and layered composites

Purpose – The purpose of the paper was to present a comparative study on the microstructure and magnetoelectric effect of new magnetoelectric composites based on TbFe2 compound and Ni0.3Zn0.62Cu0.08Fe2O4, CoFe2O4 ferrites as a magnetostrictive phase, Pb(Fe1/2Ta1/2)O3 (PFT), Pb(Fe1/2Nb1/2)O3 relaxors as a ferroelectric phase and polyvinylidene fluoride (PVDF) as piezoelectric phase. Design/methodology/approach – The ceramic components of composites were prepared by the standard solid-state reaction method. The intermetallic compound TbFe2 was prepared with an arc melting system with a contact-less ignition in a high purity argon atmosphere. The metal – ceramic – polymer composites were prepared in a container in which powder of PVDF were dissolved in N,N-dimethylformamide with continuous mixing and at the controlled temperature. Ceramic composites were prepared as bulk samples and multilayer tape cast and co-sintered laminates. The microstructure of the composites was investigated using scanning electron microscopy (SEM). The magnetoelectric effect of the composites was evaluated at room temperature by means of the dynamic lock-in method. Findings – SEM analysis revealed a dense, fine-grained microstructure and uniform distribution of the metallic, ferrite and relaxor grains in the bulk composites. The SEM image for multilayer composite illustrates the lack of cracks or delaminations at the phase boundaries between the well-sintered ferrite and relaxor layers. For all studied composites, the magnetoelectric coefficients at a lower magnetic field increase, reaches a maximum and then decreases. Originality/value – The progress in electronic technology is directly linked to advances made in materials science. Exploring and characterizing new materials with interesting magnetoelectric properties, in the rapidly growing field of functional materials, is an important task. The paper reports on processing, microstructure and magnetoelectric properties of novel magnetoelectric composites.

An investigation of magnetoresistivity properties of an Y3Ba5Cu8Oy bulk superconductor

A bulk ceramic superconducting sample was fabricated using the standard solid state reaction (SSR) method in the stoichiometric ratio of Y:Ba:Cu:O (3:5:8). The electrical and microstructural properties of the sample were investigated by means of magnetoresistivity (R-T) and micrograph measurements, respectively. Critical temperatures (Tc) such as onset and offset, irreversibility magnetic field (Hirr), upper critical magnetic field (Hc2), and activation energy (U0) were determined from the R-T under various values of applied magnetic field. The findings obtained were compared with a standard Y:Ba:Cu:O(1:2:3) superconducting sample fabricated by the SSR method. Tconset was 95.83 K for the Y358 sample and 94.86 K for the Y123 sample without the magnetic field. Tcoffset decreased from 92.87 to 74.08 K for the Y358 sample and from 82.83 to 32.44 K for the Y123 sample when the magnetic field ranged from 0 to 5 T. U0 values of Y358 and Y123 samples without the magnetic field were respectively 1.1486 and 0.3166 eV. These results indicate that the Y358 sample could provide significant benefits for high temperature superconductivity applications in future.

Electrochemical Performance and Stability of Manganese Doped La0.1Ca0.9TiO3 Anode of SOFC

Manganese doped Lanthanum calcium titanate (La0.1Ca0.9Ti1-xMnxO3, LCTM, x= 0 – 0.8) perovskites were synthesized using a standard solid state reaction method. The crystallinity and microstructures were analyzed using X-ray diffraction and SEM. Furthermore, the electrical conductivity was measured under different PO2 atmosphere via a 4-probe method. LCTM was then screen printed onto a YSZ support, as the anode, to analyze the catalytic activity for both hydrogen oxidation and methane reforming reaction. On increasing manganese doping, the lattice parameter of the perovskite phase decreased due to smaller ionic radii of manganese compared to titanium. In addition, both electrical conductivity and power density were improved with increasing manganese doping up to a certain composition. Multi-oxidation states (likely to be oxidized) of manganese increased the concentration of oxygen vacancy and relative Ti4+ concentration compared to Ti3+, thus the electrochemical performance was improved. However, the electrical conductivity decreased with further increasing manganese doping due to decrease in the absolute concentration of titanium. In this work we study the effect of manganese doping on LCT, and analyzed the electrochemical and physical behavior of the material under anodic atmosphere.

Synthesis, phase stability and oxide ion conductivity of Ce(IV)–Cd(II) double substituted bismuth vanadate

Bi4V2O11-δ has been doped with Ce and Cd to study double substitution. The system with various dopant concentrations (0.07 ≤ x ≤ 0.30) was prepared by the standard solid-state reaction method. The correlation between the polymorphism and oxide ion performance was well investigated as a function of temperature and composition with the help of thermal analysis, X-ray diffraction (XRD) and AC impedance spectroscopy. From XRD results it is seen that the high oxide ion conducting tetragonal γ-phase is stabilized for x = 0.17. For the compositions x ≤ 0.10, monoclinic α-phase is retained at room temperature with clear evidence for two successive phase transitions α ↔ β and β ↔ γ. For x = 0.13, β ↔ γ phase transition is seen. However, the existence of order–disorder, γ' ↔ γ transition was confirmed for x = 0.17. It is seen that the highest low-temperature ionic conductivity at 320 °C is 3.19 × 10−4 S cm−1 which was observed for x = 0.17.

Effects of La-doping on the ferrimagnetism in double perovskite Y2MnCrO6

The La3+ doped Y2-2yLa2yMnCrO6 (y = 0–0.4, 0.9) polycrystalline samples have been synthesized by means of a standard solid-state reaction method. For lightly doped samples with y ≤ 0.3, the refined structural parameters of XRD patterns display a decrease tendency of structural anisotropy with increasing La content, suggesting a gradual reduction of the octahedral tilting in the compounds with increasing A-site cation size. The temperature dependence of magnetization gives that the ferrimagnetic state at temperatures below ∼75 K for the prototype Y2MnCrO6 remains till y = 0.3, while the samples with y = 0.4 and 0.9 show a much higher transition temperature at ∼120 K. However, for the ferrimagnetic samples with y ≤ 0.2, a detailed analysis on the high-temperature paramagnetic susceptibility reveals that the antiferromagnetic coupling within the Cr3+ sublattice is obviously enhanced with increasing La3+ content, which is an unfavorable factor for the ferrimagnetism. The electrical transport properties of the samples are dominated by the thermal activation mechanism, and the activation energy decreases distinctly with increasing y (y ≤ 0.3). The results indicate that the ferrimagnetism in Y2MnCrO6 oxide is suppressed with increasing A-site average cation size.

Investigation on the effect of ferrite content on the multiferroic properties of (1-x) Ba0.95Sr0.05TiO3 – (x) Ni0.7Zn0.2Co0.1Fe2O4 ceramic composite

(1-x) Ba0.95Sr0.05TiO3 – (x) Ni0.7Zn0.2Co0.1Fe2O4 magnetoelectric composites are synthesized by the standard solid state reaction method and are investigated in detail. X-ray diffraction (XRD) analysis confirms the successful formation of the composites. The results of scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) reveal that NZCF phase is well dispersed in the BST matrix and has larger average grain size. The dielectric constant variation with frequency demonstrates dispersion in the low frequency region which may be ascribed to the Maxwell–Wagner interfacial polarization. Besides, the dielectric constant vs. Temperature plots of the composites exhibit ferroelectric to paraelectric phase transition, which is dependent on the NZCF content. A sharp transition peak is observed for low ferrite content, whereas for higher ferrite content, it seems to be suppressed. The maximum value of the piezoelectric coefficient (d33) obtained for the composites is 25 pC/N. With increasing NZCF content in the composites, the ferromagnetic properties get stronger while, ferroelectric behavior is gradually weakens. The observed behavior of magnetoelectric coefficient (αE) is explained in terms of variation of the resistivity of the composites and the ferrite concentration and maximum αE achieved is 2.58 mV/cm Oe for the composite with 70% BST + 30% NZCF.

Investigation of structural and temperature dependent electromagnetic properties of Co0.5Zn0.5CrxFe2−xO4

Mixed ferrites with nominal chemical compositions Co0.5Zn0.5CrxFe2−xO4 ranging from x=0 to 0.5 in the steps of 0.1 have been prepared by the standard solid state reaction method. XRD patterns confirm single phase and formation of cubic spinel structure. The lattice constant (a0), average grain size (D) and bulk density (ρB) are decreased with increasing Cr content. The ρB decreases with Cr content due to lighter atomic weight. On the other hand, both D and ρB of each composition increase with increasing sintering temperature (Ts). All samples show reentrant spin glass transition at low temperature in zero field cooled magnetization. The saturation magnetization (Ms) and Néel temperature (TN) decrease with Cr substitution due to weakening the super-exchange interaction. The coercivity (Hc) increases with increasing Cr content for various Co0.5Zn0.5CrxFe2−xO4. It may be attributed to the effect of decreasing D. Frequency dependent initial permeability (μ′i) decreases with increasing Cr content. The Ms and ρB play an important role in changing μ′i. On the other hand, the μ′i for each composition increases with increasing Ts. The highest relative quality factor (Q) is observed for various Co0.5Zn0.5CrxFe2−xO4 sintered at 1573K. The DC electrical resistivity (ρDC) of these samples increases with increasing Cr content due to decreasing Fe3+ ions at B-site.

Enhanced multiferroic properties in (1–y)BiFeO3–yNi0.50Cu0.05Zn0.45Fe2O4 composites

Multiferroic composites (1–y)BiFeO3–yNi0.50Cu0.05Zn0.45Fe2O4 (y=0.0, 0.1, 0.2, 0.3 and 0.4) are synthesized by the standard solid state reaction method. The X-ray diffraction analysis affirms the formation of both the component phases and also reveals that there is no chemical reaction between them. From the energy-dispersive X-ray spectroscopy study it is observed that the percentage of the elements in the component phases is well consistent with the nominal composition of the composites. Field Emission Scanning Electron Microscopy analysis shows almost homogeneous mixture of the two phases. The real part of the initial permeability increases (up to 67%) and the loss decreases with the ferrite content in the composites which is important in application point of view. Dielectric constant (ε′), loss tangent and AC conductivity are measured as a function of frequency at room temperature. The highest ε′ is obtained for 0.6BiFeO3–0.4Ni0.50Cu0.05Zn0.45Fe2O4 composite. The dielectric dispersion at lower frequency (<105Hz) is due to the interfacial polarization. The complex impedance spectroscopy is used to correlate between the electrical properties of the studied samples with their microstructures. Two semicircular arcs corresponding to both grain and grain boundary contribution to electrical properties have been observed in all the studied samples. The maximum magnetoelectric voltage coefficient is found to be ∼38mVcm−1Oe−1 for the composite with 80% ferroelectric+20% ferrite phases. The present composite might be a promising candidate as multiferroic materials showing effective electric and magnetic properties.

Synthesis, electrical and magnetic characteristics of Nd-modified BiFeO3

The polycrystalline Nd-modified bismuth ferrite BiFeO3 (Bi1−xNdxFeO3 (BNFO) (x=0, 0.05, 0.15, and 0.25)) were prepared in a single-phase using a standard and cost effective solid-state reaction method. In order to check the quality and formation of the compounds x-rays diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray spectroscopy (EDAX) techniques were used. Preliminary structural analysis indicates that the crystal structure of BNFO is rhombohedra for its low content of Nd (x=0, 0.05, 0.15) whereas for higher content (x=0.25) it is tetragonal. The dielectric and ferroelectric properties of BiFeO3 (BFO) were dramatically enhanced on the above Nd-substitutions. Study of the frequency dependence of ac conductivity suggests that the materials obey Jonscher׳s universal power law. An increase in Nd-content in BNFO results in the enhancement of spontaneous magnetization of BFO because of the collapse of spin cycloid structure.

Synthesis, structural characterization, electric and magnetic behaviour of a Sr2DyNbO6 double Perovskite

Many multifunctional properties have been the focus of our interest in Perovskite research. Herein, we report synthesis and characterization of a new Sr2DyNbO6 Perovskite-like material. Samples were produced via standard solid-state reaction method. Rietveld refinement of X-ray diffraction experimental data through the GSAS code reveals that this material crystallizes in a monoclinic complex Perovskite (space group P21/n, #14) with lattice parameters a=5.730(3) Å, b=5.905(1) Å and c=8.221(0) Å. Scanning electron microscopy images reveal that samples evidence a surface with strongly diffuse granular structure. From curves of magnetization as a function of temperature, we determined the paramagnetic behaviour of this complex Perovskite in the temperature regime between 50 and 320 K. Curie fitting allows obtaining an effective magnetic moment of 10.28 μB. Polarization curves as a function of the applied electric field show a hysteretic behavior of typical dielectric loss with relative dielectric constant of 264.28 at room temperature.

Nonlinear I–V behavior in colossal permittivity ceramic:(Nb+In)co-doped rutile TiO2

The new (Nb+In) co-doped TiO2 ceramics recently stimulated considerable attention due to their colossal permittivity (CP) (~100,000). In this research, the 3mol% (Nb+In) co-doped TiO2 ceramics were synthesized by an standard solid-state reaction method. Phase structure was studied by XRD and Raman, which showed that all samples were in pure rutile phase. The elements distribution was tested by the SEM–EDS, indicating that the Nb and In ions were homogeneously distributed in the grain and grain boundary. Dielectric properties and I–V behavior analysis demonstrated that the ceramics may compose of semiconducting grains and insulating grain boundaries. The existence of CP and nonlinear I–V behavior in sample had been explained by an internal barrier layer capacitance (IBLC) model, which consists of n-type semiconductor grains and insulating grain boundaries.

Dynamics of the incorporation of Co into the wurtzite ZnO matrix and its magnetic properties

Bulk Co-doped ZnO (Zn1−xCoxO) samples were prepared and studied with particular emphasis on their compositions, structures, and magnetic properties. A detailed microstructural analysis was conducted to investigate the nature of Co incorporation into the wurtzite ZnO matrix. The Zn1−xCoxO ceramic samples were prepared using the standard solid-state reaction method with different Co molar concentrations of up to 30%. A Co solubility limit of approximately 23% was determined. For samples with Co concentrations greater than 23%, a segregated phase identified as Zn-doped CoO (Co1−yZnyO with y=0.23) was observed. The magnetic characterization for the single-phase samples revealed a paramagnetic behavior with antiferromagnetic coupling of Co2+ ions within the ZnO matrix. In order to get more insight about the magnetic results Monte Carlo simulations were conducted for different magnetic couplings and different Co distributions over the volume of the samples. We discussed the observed magnetic behavior of our samples by considering the main theories regarding the magnetic properties of dilute magnetic oxides. An inhomogeneous distribution of Co ions within the grains was inferred from the microstructural and magnetic characterization.

Electrical conductivity and dielectric relaxation in Pr2CoZrO6 double perovskite

Sample of Pr2CoZrO6 (PCZ) was synthesized through the standard solid state reaction method. X-ray diffraction experiments and least square-like analysis reveal that the material crystallizes in an orthorhombic structure. SEM image displayed well-defined regular shaped spherical grains with average grain-size 0.615μm. Frequency dependence of impedance and electric modulus properties are studied over a wide frequency range of 44Hz to 1MHz at various temperatures to confirm the contribution from grain and grain-boundary. Impedance data are presented in the Nyquist plot which is used to identify an equivalent circuit and fundamental circuit parameters. Scaling behavior of the impedance data suggests that the relaxation describes the same mechanism at various temperatures. The ac conductivity data has been analyzed by fitting the data into Jonscher power law and the conduction in this system is interpreted as due to small polaron hopping. Summerfield scaling plot is used to investigate Arrhenius temperature dependence of conductivity.

Magnetic properties of a new vanadate Cu13Fe4V10O44

A new double vanadate, Cu13Fe4V10O44, obtained by standard solid-state reaction method, has been studied by magnetic susceptibility and electron paramagnetic resonance (EPR) techniques. Measurements of dc susceptibility in ZFC and FC modes in 2-300K temperature range as well as magnetization in magnetic fields up to 70kOe have revealed complex magnetic behavior and transition to the antiferromagnetic phase below 2.7K. The value of the effective magnetic moment calculated from static magnetization measurements was significantly smaller than expected from nominal valences of iron and copper ions indicating strong antiferromagnetic correlations and interactions in clusters or chains of magnetic ions even at high temperature. Although the paramagnetic phase covers a broad temperature range (3–300K) it differs in many aspects at low and high temperatures. Temperature dependence of EPR parameters (g-factor, linewidth, integrated intensity) obtained by fitting the experimental spectrum with Lorentzian lineshape point to the presence of antiferromagnetic dimers in the high-temperature range, strong antiferromagnetic correlations in the paramagnetic phase and critical slowing down of the spin fluctuations on approaching Neel temperature as well as the appearance of magnetically isolated iron ions in the antiferromagnetic phase.

Fabrication and Investigation of Structural, Magnetic and Dielectrical Properties of Zn Substituted Co-ferrites

In the present work a series of six samples of Zn substituted Co-ferrites with general formula Co1-xZnxFe2O4 where (x= 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were prepared by standard solid state reaction method. Structure, surface morphology, magnetic and dielectric properties were determined by XRD, FTIR, SEM, VSM, and LCR-meter respectively. Single phase spinel structure was confirmed by XRD. The parameters extracted from XRD revealed an increasing trend of lattice constant and X-Ray density as Zn concentration increases because atomic radius of Zn is greater than that of Co. FTIR spectra show two absorption bands in the wave number range from 500 to 1000 cm-1 which is a typical characteristic of ferrites. Uniform and well-defined particle size was observed in SEM micrographs. MH loops showed that the value of saturation magnetization (Ms) first increases up to x=0.4 (having maximum value) and then decreases because of increasing concentration of non-magnetic Zn ions. Dielectric parameters of all the samples such as tangent loss, dielectric constant were also obtained.

Synthesis, crystal structure and properties of a new barium calcium borate, Ba2Ca2(B2O5)2

A new mixed alkaline earth metal borate, Ba2Ca2(B2O5)2, has been synthesized by standard solid-state reaction method and the crystal structure has been determined by the single crystal X-ray diffraction method. It crystallizes in the monoclinic system, space group P21/c (No. 14) with a = 6.568(2) Å, b = 20.545(7) Å, c = 8.201(2) Å, β = 117.00(2) °, and Z = 4. The structure contains an infinite three-dimensional (3D) matrix that is built up of BaOn (n = 7, 9) polyhedra, CaO6 octahedra and isolated B2O5 groups. Specifically, the configuration and arrangement of the B2O5 groups are discussed comparing with those in other two alkaline earth metal borates, MgSrB2O5 and Mg3Ca3(B2O5)3. Thermal stability measurements reveal that Ba2Ca2(B2O5)2 melts incongruently at 1015 °C. Optical properties of Ba2Ca2(B2O5)2 were investigated and the first-principle theoretical calculations were performed to understand the electronic structure.