Single Step Solid State Reaction Research Articles

Electrical and Magnetic Behaviour of PrFeAsO $_{\mathbf{0.8}}$ F $_{\mathbf{0.2}}$ Superconductor

The superconducting and ground state samples of PrFeAsO0.8F0.2 and PrFeAsO have been synthesised via the easy and versatile single step solid state reaction route. X-ray and Reitveld refine parameters of the synthesised samples are in good agreement to the earlier reported value of the structure. The ground state of the pristine compound (PrFeAsO) exhibited a metallic-like step in resistivity below 150 K followed by another step at 12 K. The former is associated with the spin density wave (SDW)-like ordering of Fe spins and later to the anomalous magnetic ordering for Pr moments. Both the resistivity anomalies are absent in case of the superconducting PrFeAsO0.8F0.2 sample. Detailed high field (up to 12 Tesla) electrical and magnetization measurements are carried out for the superconducting PrFeAsO0.8F0.2 sample. The PrFeAsO0.8F0.2 exhibited superconducting onset ( $T_{c}^{\mathrm{onset}}$ ) at around 47 K with T c (ρ=0) at 38 K. Though the $T_{c}^{\mathrm{onset}}$ remains nearly invariant, the T c (ρ=0) is decreased with applied field, and the same is around 23 K under an applied field of 12 Tesla. The upper critical field (H c2) is estimated from the Ginzburg–Landau equation (GL) fitting, which is found to be ∼182 Tesla. Critical current density (J c ), being calculated from high field isothermal magnetization (MH) loops with the help of Beans critical state model, is found to be of the order of 103 A/cm2. Summarily, the superconductivity characterization of the single step synthesised PrFeAsO0.8F0.2 superconductor is presented.

Influence of Nano-Ag Addition on the Mechanical Properties of (Cu0.5Tl0.5)-1223 Superconducting Phase

Superconducting samples of type (nano-Ag) x Cu0.5Tl0.5Ba2Ca2Cu3O10−δ , x=0.0,0.5,1.0,1.5,2.0, and 3.0 wt.% of the total sample’s mass were prepared by a single step solid-state reaction technique. The prepared samples were characterized using X-ray powder diffraction (XRD) and a scanning electron microscope (SEM). The electrical properties of the prepared samples were investigated using the electrical resistivity and I–V measurements. The Vickers microhardness (H v ) was measured at different applied loads (0.25–3.0 N) for studying the mechanical performance of the prepared samples. All prepared samples exhibited normal indentation size effect (normal ISE) and the H v number was load dependent. H v number increases as nano-Ag addition increased. The experimental data of H v was analyzed using different models; Mayer’s law, Hays–Kendall (H–K) approach, elastic/plastic deformation (EPD) model, proportional specimen resistance (PSR) model, and indentation induced cracking (IIC) model. In addition, the true microhardness (H o ) values were evaluated through different models. The obtained data has good agreement with the PSR model. Also, Young’s modulus (E), yield strength (Y), fracture toughness (K f ), and brittle index (B i ) were calculated.

Influence of Nano-Ag Addition on Phase Formation and Electrical Properties of (Cu0.5Tl0.5)-1223 Superconducting Phase

Superconducting samples of type (nano-Ag)xCu0.5Tl0.5Ba2Ca2Cu3O10−δ, x=0.0, 0.5, 1.0, 1.5, 2.0 and 3.0 wt.%, were prepared under ambient pressure via a single step solid-state reaction technique at 850 °C. The prepared samples were characterized by means of X-ray powder diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray (EDX) and differential scanning calorimetry (DSC). The electrical properties of the prepared samples were investigated using the electrical resistivity and I–V measurements. The low addition of nano-Ag up to x=1.5 wt.% enhanced the phase formation and improved the superconducting transition temperature Tc, critical current density Jc, and melting temperature. For x>1.5 wt.%, a reverse trend was observed.

The excess conductivity of (Cu0.5Tl0.5)-1223 superconductor substituted by Ti

Superconducting samples of nominal composition of (Cu0.5Tl0.5−xTix)Ba2Ca2Cu3O10−δ (x=0.0, 0.05, 0.10, 0.15, 0.20 and 0.25) were prepared by a single step solid-state reaction technique at ambient pressure. The prepared samples were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM) and electron dispersive X-ray (EDX). XRD analysis indicated that the volume fraction of (Cu0.5Tl0.5)-1223 increases from 85.6% to 88.2% with increasing of x up to 0.10. The superconducting transition temperature, Tc determined from electrical resistivity data, increases from 122.9 to 125.3K as x increases from 0.0 to 0.10 and then it decreases to 116.5K for x=0.25. The excess conductivity analysis of these samples was analyzed with Aslamazov–Larkin (AL) theory. Four different regions were clearly appeared as the temperature was lowered, namely short wave (sw), two dimensional (2D), three dimensional (3D) and critical (cr) fluctuations. The superconducting parameters were calculated from excess conductivity analysis as a function of Ti substitution. The zero temperature coherence length along the c-axis, ξc(0) and the interlayer spacing, d decrease as x increases up to x=0.10 and then they increase with further increase in x. All the estimated interlayer coupling values are less than one, confirming the weak coupling between CuO2 planes and crossover between 3D and 2D regions.

Thermomechanical Analysis of (Cu0.5Tl0.5)-1223 Substituted by Pr and La

The thermomechanical analysis (TMA) of Cu0.5Tl0.5Ba2a2−xRxCu3O10−δ, where R=Pr and La, with 0.0≤x≤0.15, was carried out in temperature range from 450 to 1145 K. The samples were prepared by single-step solid state reaction technique. The prepared samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The superconductivity of the prepared samples was investigated by electrical resistivity measurement. The results showed that low substitution content enhanced the (Cu0.5Tl0.5)-1223 phase formation, while the higher substitution content degraded this phase. The higher superconducting transition temperatures Tc were found to be 114 K and 109 K at x= 0.025 for Pr- and La-substitutions, respectively The average linear thermal expansion coefficient increased as x increased, while the shrinkage temperature decreased as x increased. Those results were emphasized by porosity and Vickers microhardness calculations. Debye temperature θD was calculated from the linear thermal expansion coefficient data and correlated to Tc to estimate the electron-phonon coupling λep.

Mechanical Properties of (Cu0.5Tl0.5)-1223 Substituted by Pr

Cu0.5Tl0.5Ba2Ca2−xPrxCu3O10−δ superconducting samples, with 0≤x≤0.15, were prepared by a single-step solid state reaction on a form of rectangular bar. The prepared samples were characterized using X-ray powder diffraction (XRD) and scanning electron microscope (SEM). The room temperature Vickers microhardness was measured at different loads (0.25–3 N). The experimental results were analyzed using Meyer’s law, Hays–Kendall approach, elastic/plastic deformation model, proportional specimen resistance model, and the indentation-induced cracking (IIC) model. Surprising results were obtained and showed that all samples in the form of rectangular bars exhibited reverse indentation size effect in contrary with those in the form of discs. Vickers microhardness values were decreased as Pr-content increased that consisting with the porosity results. Furthermore, the Young’s modulus was determined using the dynamic resonance technique. A relation between Young’s modulus (E) and Vickers microhardness (HV) was obtained.

Excess Conductivity Analysis of (Cu0.5Tl0.5)-1223 Substituted by Pr and La

Series of superconducting samples of type Cu0.5Tl0,5 Ba2Ca2−yRy Cu3O10−δ, where R = Pr and La with 0 ≤ y ≤ 0.20, were prepared in a sealed quartz tube via a single-step solid-state reaction technique. The prepared samples were char- acterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), and electron dispersive X-ray (EDX). XRD studies indicated that the tetragonal struc- ture of (Cu0.5Tl0.5)-1223 phase does not change by Pr or La-substitutions whereas the lattice parameters a and c do. The elemental compositions analysis, determined from EDX, indicated that both Pr and La were successfully introduced into the mi- crostructure of (Cu0.5Tl0.5)-1223 phase. The electrical resistivity ρ(T )was measured as a function of temperature using conventional dc four-probe technique. The fluc- tuation conductivity �σ , above the superconducting transition temperature Tc ,w as analyzed as a function of temperature using Aslamazov and Larkin model. It ex- hibits four different fluctuation regions namely critical (cr), three-dimensional (3D), two-dimensional (2D), and short-wave (sw). The zero-temperature coherence length, effective layer thickness of the two-dimensional system and inter-layer coupling strength were estimated as a function of the substitution-content y. Furthermore, the thermodynamics critical field, lower critical magnetic field, upper critical magnetic field, critical current density and Fermi energy were calculated from the Ginzburg number. The data indicated that both Pr and La-substitutions have quite similar be- haviors.

An Indicator to Identify the Li [ Ni1 / 2Mn3 / 2 ] O4 ( P4332 ) : DC-Susceptibility Measurements

To gain an insight into the inter-relationship between the electrochemical properties and the magnetism of , the magnetic nature of two different samples was investigated by dc-susceptibility measurements. One was prepared by a single-step solid-state reaction technique [ in a cubic phase (LNMO-C)], while the other was prepared by a two-step solid-state reaction technique [ (LNMO-P)]. According to the structural and electrochemical analyses, LNMO-C was assigned as “nonstoichiometric ,” whereas LNMO-P was assigned as stoichiometric . Both samples exhibited a ferromagnetic (FM) behavior below . However, the FM parameters for LNMO-P, such as saturation magnetization and transition temperature , were apparently different from those for LNMO-C. This suggests that magnetic measurements are a powerful tool to distinguish the stoichiometric from the nonstoichiometric phase.

Superconductivity at 14 K in SmFe0.9Co0.1AsO

We report superconductivity in the SmFe0.9Co0.1AsO system being prepared by most easy and versatile single-step solid-state reaction route. The parent compound SmFeAsO is non-superconducting but shows the spin density wave (SDW) like antiferromagnetic ordering at around 140 K. To destroy the antiferromagnetic ordering and to induce the superconductivity in the parent system, the Fe2+ is partially substituted by Co3+. Superconductivity appears in SmFe0.9Co0.1AsO system at around 14 K. The Co doping suppresses the SDW anomaly in the parent compound and induces the superconductivity. Magnetization measurements show clearly the onset of superconductivity with Tcdia at 14 K. The isothermal magnetization measurements exhibit the lower critical fields (Hc1) to be around 200 Oe at 2 K. The bulk superconductivity of the studied SmFe0.9Co0.1AsO sample is further established by open diamagnetic M(H) loops at 2 and 5 K. Normal-state (above Tc) linear isothermal magnetization M(H) plots excluded the presence of any ordered magnetic impurity in the studied compound.

Effect of Sm-substitution on the electrical and magnetic properties of (Tl 0.8Hg 0.2)-1223

Bulk Tl 0.8Hg 0.2Ba 2Ca 2− x Sm x Cu 3O 9− δ superconducting samples with x = 0.00, 0.025, 0.05, 0.10, 0.15, and 0.20 were prepared, in a sealed quartz tube, by a single step solid-state reaction technique. The prepared samples were investigated using X-ray powder diffraction, scanning electron microscope, electron dispersive X-ray, electrical resistivity, ac magnetic susceptibility and electron paramagnetic resonance. Powder X-ray diffraction analysis revealed that the prepared samples are nearly single phase of (Tl, Hg)-1223 with tetragonal structure (space group P/4 mmm). The temperature dependence of the electrical resistivity and the ac magnetic susceptibility was investigated to study the effect of Sm-substitution, on the superconducting transition temperature T c and the intergrain critical current density J c. The data showed a T c suppress as Sm-content increases, whereas J c increases up to x = 0.05, after that it depresses with further increase in x. Furthermore, electron paramagnetic resonance (EPR) spectrum at room temperature was studied for the prepared samples. The values of the gyromagnetic factors, g ⊥, g ∥, the hyperfine structure and the spin density were calculated as a function of Sm-content.

Enhancement the formation of (Cu, Tl)-1223 superconducting phase by Cd-substitution

Cu 0.5Tl 0.5Ba 2Ca 2− x Cd x Cu 3O 10− δ superconductor samples ( x = 0–0.8) were prepared by a single-step solid-state reaction technique in order to investigate the effect of Cd-substitution on the formation and the transport properties of the (Cu, Tl)-1223 phase. A nearly single-phase materials is synthesized with x = 0.2 and found to have optimum superconducting transition temperature T c and critical current density J c. The dielectric constant and the loss tangent, for all the prepared samples, were measured at room temperature as a function of frequency up to 5 MHz. The normal dielectric constant is strongly dependent on Cd-content and correlates with the normal electrical resistivity results. This correlation was discussed according to the grain boundaries scattering.

Spectroscopic characterization of zinc oxide nanorods synthesized by solid-state reaction

Well-crystallized zinc oxide nanorods have been fabricated by single step solid-state reaction using zinc acetate and sodium hydroxide, at room temperature. The sodium lauryl sulfate (SLS) stabilized zinc oxide nanorods were characterized by using X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and photoluminescence spectroscopy. The X-ray diffraction revealed the wurtzite structure of zinc oxide. The size estimation by XRD and TEM confirmed that the ZnO nanorods are made of single crystals. The growth of zinc oxide crystals into rod shape was found to be closely related to its hexagonal nature. The mass ratio of SLS:ZnO in the nanorods was found to be 1:10 based on the thermogravimetric analysis. Blue shift of photoluminescence emission was noticed in the ZnO nanorods when compared to that of ZnO bulk. FT-IR analysis confirmed the binding of SLS with ZnO nanorods. Apart from ease of preparation, this method has the advantage of eco-friendliness since the solvent and other harmful chemicals were eliminated in the synthesis protocol.

Electric resistivity and magnetic susceptibility studies of Tl-1223 substituted bycobalt

Bulk superconductor samples of typeTlBa2Ca2(Cu3−xCox)O9−δ with were prepared by a single-step solid-state reaction. The prepared samples were characterized bypowder x-ray diffraction and the superconductivity of these samples was investigated by electricalresistivity and ac magnetic susceptibility. The x-ray data indicate that the lattice parametersa and c vary but the structure of Tl-1223 remains tetragonal with cobalt substitution up tox = 0.6. The transitiontemperature ‘TC ’, deduced from electrical resistivity and ac magnetic susceptibility measurements,is suppressed by substituting Co impurities at Cu sites. The suppression inTC has been discussed using a Cooper pair-breaking mechanism due to the Abrikosov andGrokov model. The effects of external magnetic field on the ac magnetic susceptibility aswell as calculations of critical current density as a function of cobalt content andtemperature are reported.

Melt-textured Bi1.6Pb0.4Sr2Ca2Cu3O11 bulk superconductors fabricated in a simple tube furnace

Using the simplified version of the melt-textured growth (MTG) technology with a simple tube furnace, we have fabricated superconductors satisfying the nominal composition Bi1.6Pb0.4Sr2Ca2Cu3O11. We would note that the material used in the fabrication was prepared by mixing a precursor Bi1.6Pb0.4Sr2Cu3O x and CaO powder. This two step technique was found to be superior to the single step solid state reaction method after many trials. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) morphologies show that the melt-textured bulk samples are made up of stacks of highly textured single crystal-like layers. X-ray analysis as well as d.c. magnetization measurements were carried out and theJ c value was found to be 1.3×103 A cm−2 at 77 K using the Bean model. At this stage, thoughJ c is not so high as that of the best samples obtained from other complicated methods involving special (hot) pressing and sintering techniques, we do not need to apply any mechanical treatment at or after the heating procedure.

Synthesis and properties of superconducting HgBa2CuO4+x from a single-step low-temperature solid state reaction

A novel technique based on a low-temperature single-step solid state reaction of stoichiometric quantities of HgO and Ba2CuO3 to produce superconducting HgBa2CuO4+x samples has been developed. The 'as-prepared' polycrystalline Hg-1201 samples had a Tc of 95 K, as obtained by the diamagnetic onset and resistivity measurements. The crystal symmetry was tetragonal with lattice parameters a=3.876(1) AA, and c=9.509(4) AA in agreement with literature data. Sample morphology consists of grains (average dimension 30 mu m) larger than in previously published works and of a needle-like structure embedding the whole sample. These results were highly reproducible over several batches. The resistive transition in magnetic field up to 8 T and a set of magnetic measurements is presented. From these measurements we obtain information about the irreversibility line, the critical current field dependence and the presence of weak links.