Standard Solid-state Reaction Method Research Articles

Influence of Cu-site substitution on La2Ca1Ba2Cu5Oz superconducting system

We have prepared a series of La2CaBa2Cu5-xCoxOz; x = 0.0, 0.1, 0.2, 0.5, 1.0, 2.0, 5.0 (La-2125) compounds by the standard solid state reaction method and characterized for their structural, superconducting, magnetic properties and oxygen content through X-ray diffraction, scanning electron microscopy, d. c. resistivity, magnetic susceptibility and iodometric titration respectively. All the compounds crystallize with the tetragonal LaBa2Cu3Oz type structure, space group P4/mmm. Here the effect of higher Co substitution for Cu in the La2CaBa2Cu5-xCoxOz system has been studied. It is observed that only 2 at. % Co substitution for Cu destroys the superconductivity of the sample. For heavily doped samples (with x ≥ 0.1) are found non-superconducting presumably because of magnetic pair- breaking effect. These samples do not show superconductivity but are of interest for understanding the interplay between superconductivity and magnetism. Possible reasons for destruction of superconductivity are discussed in this communication.

Electric and Structural Properties of the New Ba2TiZrO6 Ferroelectric Complex Perovskite

We report the synthesis, structural characterization, morphologic and ferroelectric behavior of the Ba2TiZrO6 complex perovskite. The samples of Ba2TiZrO6 were synthesized through the standard solid-state reaction method. Rietveld analysis of X-ray diffraction patterns reveals that this material crystallizes in a rhombohedral structure, space group R-3 (#148), with cell parameter a=5.8038(7) A. Images of Scanning Electron Microscopy show the micrometric granular character of samples with 1.0 μm grain size. Results of semi-quantitative Energy Dispersive X-ray analysis are 97.5 % in agreement with the nominal stoichiometry of Ba2TiZrO6. Curves of polarization as a function of the applied electric field reveal that the Ba2TiZrO6 double perovskite behaves as a ferroelectric material at room temperature.

Synthesis, structural and electrical properties of Ti modified Bi2Sn2O7 pyrochlore

Abstract Polycrystalline ceramic samples of Bi 2 Sn 2− x Ti x O 7 ( x =0.00, 0.2, 0.4, 0.6 and 0.8) have been synthesized by standard high temperature solid state reaction method. The effect of homovalent cation (titanium) substitution on the Sn-site on the structural and electrical properties of the pure Bi 2 Sn 2 O 7 ceramic have been studied by X-ray diffraction followed by SEM, dielectric and dc conductivity studies. The structural analysis indicates that the increase of titanium contents do not lead to any secondary phase. The frequency and temperature dependent dielectric studies have been carried out. It is found that the Ti doping reduces the material particle size. The size of the particles are strongly influenced by the addition of titanium to the system. The substitution of Ti for Sn ions affected the degree of disorder and modified the dielectric properties leading to more resistive ceramic compounds. The activation energies of all the compounds were calculated using the relation σ = σ 0 exp(− Ea / kT ).

Structural, thermal, electrical and magnetic properties of pure and 50% La doped BiFeO3 ceramics

Polycrystalline ceramic samples of pure and 50% La substituted BiFeO3 have been prepared by standard solid state reaction method using high purity oxides and carbonates. The formation of the single phase compound as well as its chemical analysis has been checked by X-ray diffraction and energy dispersive X-ray microanalysis (EDAX) techniques. A better agreement between observed and calculated X-ray powder diffraction patterns was obtained by performing the Rietveld refinement with a structural model using the non-centrosymmetric space group R3c. The lattice parameters in both the cases have been refined but the over-all structure remains the same. The microstructural studies have been carried out using scanning electron microscopy (SEM). Modulated differential scanning calorimetry (MDSC) has been used to detect the Neel/transition temperature in the compounds. The activation energies calculated from log σ vs 1/T curve are 0.81 eV and 1.13 eV respectively. Vibrating sample magnetometer (VSM) has been used to study the magnetic behaviour of the compounds. It has been observed that by 50% La substitution the insulating behaviour of the material has been improved and showing the antiferromagnetic to weak ferromagnetic behaviour.

Structural and vibrational studies of Ca-doped Ba2TiSi2O8 ceramics

Polycrystalline ceramic samples of calcium (Ca2+) substituted barium titanium silicate mineral (fresnoite) of general formula Ba2−xCaxTiSi2O8 (x=0.0, 0.2, 0.4, 0.8 and 1), have been prepared by standard solid state reaction method using high purity oxides and carbonates. The formation of the single phase compound and its structural parameters were investigated by X-ray diffraction followed by Rietveld refinement. The lattice parameters calculated using the Rietveld refinement analysis are better than that of the earlier report so far. Raman spectra measured at 300K for tetragonal Ba2−xCaxTiSi2O8 ceramics present well defined modes. The variations of the Raman modes with the different concentration of Ca2+ substitution have been studied in detail.

Dielectric, modulus and impedance analysis of lead-free ceramics Ba0.8La0.133Ti1−x Sn x O3 (x=0.15 and 0.2)

Titanate barium (BaTiO3)-type oxide ceramics Ba0.8La0.133Ti1−x Sn x O3 (BLTS) (here x=0.15 and 0.2) have been synthesized by the standard solid-state reaction method. Preliminary room temperature X-ray study confirms the formation of single-phase compounds in a rhombohedral crystal system. The electrical properties of BLTS were studied using the ac impedance spectroscopy technique over a wide range of temperature (120–320 K) in the frequency range of 40 Hz to 10 MHz. The presence of a single arc in the complex modulus spectrum at different temperatures confirms the single-phase character of the BLTS compounds.

Superconducting Properties of Hg0.8Cu0.15Sb0.05Ba2Ca2Cu3O8+δ Ceramic with Controlling Sintering Conditions

Hg0.8Cu0.15Sb0.05Ba2Ca2Cu3O8+δ High temperature superconducting samples were prepared by using a standard solid-state reaction method with different sintering temperatures of 1073, 1093, 1113, 1133 and 1153 K. The electrical resistivity measurements showed that the sintering conditions have major effects on the transition temperature of the superconducting compound. The samples prepared at 1113 and 1153 K have transition temperatures at zero resistivity Tc(offset)=107,112 K and Tc(onset)=121,128 K respectively. Meanwhile, the sample prepared at 1133 has highest transition temperature Tc(offset)=121 K and Tc(onset)=134 K. However, the samples which were prepared at 1073 and 1093 K showed metallic behavior with respect to temperature, but this could not help us to obtain the values of Tc(off) because they were less than the point of liquid nitrogen. The effect of sintering times on the transition temperature has been investigated by using the samples prepared at 1133 K. The value of Tc(offset) at the sintering times of 16–24 hours rises from 121 K to 126 K. The XRD data collected from various samples were all polycrystalline. It was found that the increase of sintering temperatures from 1073–1153 K caused an extremely high amount of decomposition of the low-phase (1212) superconductor and produced high-phase (1223) superconductors. The oxygen content (δ), volume fraction VPh(1223) and the lattice parameters were changing with the increase of the sintering temperature.

Ferroelectric properties and ac conductivity studies of yttrium modified Pb(Fe0.5Nb0.5)O3 ceramics

Using a high-temperature standard solid-state reaction (i.e., mixed oxide) method several yttrium modified ferroelectric ceramics of type Pb1−xYx(Fe0.5Nb0.5)1−x/4O3 (PYFN)with different concentration (x = 0.00, 0.02, 0.04, 0.06, 0.08) were prepared. Preliminary X-ray structural analysis reveals that all the samples were crystallized in monoclinic crystal system. The crystal structure is almost invariant with small Y-concentration. Microstructure of the samples exhibits grain growth on increasing Y content. Curie temperature of Y-substituted samples decreases slightly as compared to that of PFN (Pb(Fe1/2Nb1/2)O3). However, Y substitution results in a notable enlargement of remnant polarization (2Pr). The 2Pr of PYFN (x = 0.02) reaches to a large value (23 μC/cm2) which is nearly 5 times greater than that of x = 0.00 (4.6 μC/cm2). A phenomenological model (i.e., ferroelectric capacitor model) used to simulate hysteresis loops was found to be suitable to explain experimental results. Jonscher's single power law (σac(ω) = σ(0) + Aωn) was well fitted to the frequency dependence of conductivity for all the samples.

The effect of gamma irradiation on polycrystalline Y3Ba5Cu8O18

The effect of gamma irradiation on transport properties and kinetic parameters of high-temperature ceramic Y3Ba5Cu8O18 superconductor has been investigated. The bulk samples, prepared by the standard solid-state reaction method, were irradiated by gamma rays of different doses in the range 0–44.8 kGy at room temperature. The changes in transition temperature (T c ) and excess conductivity have been discussed. The effects of irradiation on surface morphology have been investigated by scanning electron microscopy. The kinetic parameters have been estimated by thermogravimetric analysis.

Tunable magnetocaloric effect near room temperature in La0.7-xPrxSr0.3MnO3 (0.02 ≤ x ≤ 0.30) manganites

We have systematically investigated the compositional dependence of the magnetic and magnetocaloric properties of La0.7-xPrxSr0.3MnO3 (LPSMO). Polycrystalline samples of LPSMO with 0.02 ≤ x ≤ 0.30 were prepared by a standard solid-state reaction method with phase purity and structure confirmed using x-ray diffraction. Temperature dependent magnetization measurements and Arrott analysis reveal second order ferromagnetic transitions in each sample with Curie temperature decreasing progressively with increasing Pr content from ∼350 K for x = 0.02 to ∼295 K for x = 0.30. Magnetic entropy change (ΔSM) was calculated by applying the thermodynamic Maxwell equation to a series of isothermal field dependent magnetization curves. In the sample with x = 0.30, the maximum value of −ΔSM reaches ∼2.08 J/kg K at 295 K for a field change of 1.5 T. Reduced Pr content corresponds to larger values of entropy change, reaching −ΔSM ∼2.79 J/kg K for the x = 0.02 doping. The refrigeration capacity for each composition reached sizable values of 33–48 J/kg for a small applied field of 1.5 T.

High Temperature Superconductivity on the New Superconductor System Yb1.8Sm1.2Ba5Cu8O18

The synthesis of the new high temperature superconductor system Yb1.8Sm1.2Ba5Cu8O18 is reported. The new material was produced using the standard solid-state reaction method. The structural characterization of the compound was performed by X-ray diffraction and Rietveld refinement using a polycrystalline sample of the material. Structural ordering corresponds to an orthorhombic structure, from the space group Pmm2. The lattice parameters of the material are reported here. The superconducting nature of the material was determined by measuring the magnetization, as a function of its temperature, in the regime of low and mean field. A critical temperature value of T c ∼88 K was determined for Yb1.8Sm1.2Ba5Cu8O18. The experimental results have shown that the production of a novel group RE3Ba5Cu8O18 of high-T c superconductivity is possible, by substitution of RE instead of Y in the recently reported new superconductor material Y3Ba5Cu8O18.

A Study on Magnetoresistivity, Activation Energy, Irreversibility and Upper Critical Field of Slightly Mn Added Bi-2223 Superconductor Ceramics

This study discusses the effect of Mn addition on the superconducting and physical properties in Bi1.8Pb0.4Sr2Mn x Ca2.2Cu3.0O y bulk superconductors with x=0,0.03,0.06,0.15,0.3, and 0.6 by means of the magnetoresistivity measurements. The magnetoresistivity of the samples prepared using the standard solid-state reaction method was measured for different values of the applied magnetic field strengths. The superconducting and physical properties of the samples such as the zero resistivity transition temperatures (T c ), irreversibility fields (μ 0 H irr ), and upper critical fields (μ 0 H c2) were deduced from the magnetoresistivity curves. Moreover, thermally activated flux creep model was studied for activation energy (U 0) values of the samples. According to the results of the measurements, not only were the T c and U 0 values of the samples found to decrease significantly but the μ 0 H irr and μ 0 H c2 values were also observed to reduce with the increase in the Mn addition, indicating that the doping degrades the physical and superconducting properties of the samples.

Structural, magnetic and electric behavior of the new Ba2TiMoO6 material

We report synthesis and characterization of the structural, morphologic and ferroelectric behavior of the complex perovskite Ba2TiMoO6. Samples of Ba2TiMoO6 were synthesized through standard solid state reaction methods. Crystalline structure was studied by means of X-ray diffraction experiments and Rietveld-like analysis. Results reveal that material crystallizes in a tetragonal structure, space group P4/mnm (#123), with cell parameters a=3.8557Å and c=11.8678Å. The tolerance factor of perovskite was determined to be 1.04. Surface morphology was examined using Scanning Electron Microscopy, which shows the micrometric granular character of samples with 1.0–5.0μm mean grain size. Ferroelectric response of material was established from curves of polarization as a function of applied electric field. Our results reveal that Ba2TiMoO6 double perovskite evidences a ferroelectric hysteretic behavior at ambient temperature and paramagnetic ordering. © 2011 Elsevier Science. All rights reserved.

Dielectric and Impedance Spectroscopic Studies of SrBi<sub>4-x</sub>La<sub>x</sub>Ti<sub>4</sub>O<sub>15</sub>

Ceramic samples of SrBi4-xLaxTi4O15with x=0.025 is prepared by standard solid state reaction method. The phase formation is confirmed by X-ray diffraction (XRD) studies. The Dielectric and Impedance measurement has been performed in the temperature range 50°C to 600°C and the frequency range 1Hz to 1MHz. The Curie temperature is found to decrease from 535°C to 505°C. The Cole-Cole plots are semi circles in the temperature range 450°C to600°C. The relaxation time is decreased with increase of temperature. The investigations on this material at high temperatures and frequencies reveal its stable behavior.

Study on the structural and magnetic properties of La-doped barium ferrites

Magnetic properties of La doped M-type barium ferrites are studied. The samples are prepared by the standard solid state reaction method. The influences of La3+ on structures and magnetic properties of barium ferrites (Ba1-xLaxFe12O19) are investigated. Single-phase M-type barium ferrites with chemical composition of Ba1-xLaxFe12O19 (x=0.0—0.6) are formed by sintering at 1100—1175 ℃ in air. Scanning electron microscopy (SEM) reveals that the La doping has no effect on the structure of barium ferrite. Vibrating sample magnetometer (VSM) shows that with the valaue of x increasing, the saturation magnetization (Ms) increases, reaching a maximum at x=0.2 and then decreases and the coercivity of the sample increases continuously. The value of Ms reaches a maximum value of 62.8 emu/g at x=0.2 and 1175 ℃, and the Hc reaches a maximum value of 3911.5 Oe at x=0.6 and 1125℃.

Structural, Thermal and Electrical Property of Polycrystalline LaLiMo<sub>2</sub>O<sub>8</sub>

This research article reports electrical characterization of a rare earth molybdate based on combination of rare earth (La+3) and alkali (Li+) metal ions. The experimental observation suggests the negative temperature coefficient of resistance behavior of the material. The material has been prepared by standard solid state reaction method, where the synthesis conditions have been optimized by thermal analysis. A possible mechanism for the formation of the polycrystal-line LaLiMo2O8 is reported. A systematic analysis has been done to determine the crystal structure of the powder material and it was found that the powder material was crystallized to tetragonal unit cell structure. Electrical properties have been studied using a.c. impedance measurement. The temperature variation of electrical conductivity of the material shows typical Arrhenius behavior. The activation energy evaluated from conductivity data works out to be ~0.94 ev.

Ferromagnetism in Fe-doped CuO nanopowder

The Fe-doped CuO nanopowder was synthesized by following the standard solid-state reaction method. The structure and magnetic properties of the Fe-doped CuO nanopowder were investigated. X-ray diffraction spectra confirmed the monoclinic structure of CuO and no secondary phase was detected, indicating that the Fe ions were incorporated into CuO. The ferromagnetism in Fe-doped CuO was studied and is believed to originate from the interaction between Fe ions and Cu ions via a super-exchange interaction or F-center mediated exchange interaction.

Large Magnetic Entropy Change in La0.55Ce0.2Ca0.25MnO3Perovskite

In this paper, magnetic property and magnetocaloric effect (MCE) in perovskite manganites of the type La (0.75-X) Ce X Ca 0.25 MnO 3 (x = 0.0, 0.2, 0.3 and 0.5) synthesized by using the standard solid state reaction method have been reported. From the magnetic measurements as a function of temperature and applied magnetic field, we have observed that the Curie temperature (T C ) of the prepared samples strongly dependent on Ce content and was found to be 255, 213 and 150 K for x = 0.0, 0.2 and 0.3, respectively. A large magnetocaloric effect in vicinity of T C has been observed with a maximum magnetic entropy change (|ΔSM| max ) of 3.31 and 6.40 J/kgK at 1.5 and 4 T, respectively, for La 0.55 Ce 0.2 Ca 0.25 MnO 3 . In addition, relative cooling power (RCP) of the sample under the magnetic field variation of 1.5 T reaches 59 J/kg. These results suggest that La 0.55 Ce 0.2 Ca 0.25 MnO 3 compound could be a suitable candidate as working substance in magnetic refrigeration at 213 K.

Effect of Ce Addition on the Magnetoresistivity, Irreversibility Field, Upper Critical Field and Activation Energies of Bi-2212 Superconducting Ceramics

This study aims to analyze the effect of Ce addition on the microstructural, superconducting and physical properties of Bi1.8Sr2.0Ce x Ca1.1Cu2.1O y ceramics with x=0, 0.001, 0.003, 0.005, 0.01, 0.03, 0.05 and 0.1 via X-Ray analysis (XRD), scanning electron microscopy (SEM), electron dispersive X-Ray (EDX) and magnetoresistivity measurements. The ceramics produced in this work are prepared using the standard solid-state reaction method. The zero resistivity transition temperatures (T c), activation energies (U 0), irreversibility fields (μ 0 H irr) and upper critical fields (μ 0 H c2) are determined from the resistivity versus temperature (R–T) curves under dc magnetic fields up to 7 T. The results show that T c and U 0 values of the samples are found to decrease dramatically with the increase in the Ce-content and applied magnetic field. Moreover, XRD results indicate that all the samples contain the Bi-2212 phase only and exhibit the polycrystalline superconducting phase with less intensity of diffraction lines with the increase of the Ce addition. As for the results of SEM images, the texturing, crystallinity, grain size distribution, layered grain growth and grain connectivity are observed to degrade with the increase of the Ce doping. Besides, the irreversibility fields and upper critical fields are found to degrade as Ce doping increases. Penetration depths (λ) and coherence lengths (ξ) are also discussed.

Effect of Nb substitution on the structural, dielectric and magnetic properties of multiferroic BiFe 1− xNb xO 3 ceramics

Polycrystalline BiFe 1− x Nb x O 3 ceramics have been synthesized by standard solid-state reaction method. The effect of Nb substitution on the dielectric, magnetic and magnetoelectric properties of the BiFeO 3 multiferroic perovskite was studied. X-ray diffraction pattern revealed that all the samples with x = 0.00–0.10 showed rhombohedral perovskite structure. We obtained single phase upto doping concentration of x = 0.05 and with further increase in Nb concentration, some impurity peaks appeared. An anomaly in the dielectric constant ( ɛ) and dielectric loss (tan ( δ)) in the vicinity of the antiferromagnetic Néel temperature ( T N) was observed. Nb substitution reduced the antiferromagnetic Néel temperature ( T N) in BiFe 1− x Nb x O 3. Proper amount of Nb could decrease the dielectric loss. Magnetic hysteresis loops measured at 5 K/300 K and temperature dependent magnetization curves indicated ferromagnetism in Nb substituted BiFeO 3 ceramics. The room temperature magnetic moment was found to increase with increase in Nb concentration. The dependence of dielectric constant on the magnetic field is an evidence of magnetoelectric coupling in BiFe 1− x Nb x O 3 ceramics.