Single Step Solid State Reaction Research Articles

Photocatalytic degradation of Rhodamine B dye over oxygen-rich bismuth oxychloride Bi24O31Cl10 photocatalyst under UV and Visible light irradiation: Pathways and mechanism

Photocatalytic removal of organic pollutants from wastewater has recently garnered significant attention due to its environmental and ecological significance. In this study, a bismuth-rich bismuth oxychloride (Bi24O31Cl10) was synthesized using a single-step solid-state reaction and applied as a photocatalyst for the degradation of rhodamine B in aqueous solution. The photocatalyst was prepared through an eco-friendly solid-state method by mixing bismuth oxide (Bi2O3) and bismuth oxychloride (BiOCl), followed by direct annealing at 600 °C. The synthesized material was characterized through various techniques, including X-ray diffraction (XRD), Fourier-transform infrared (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analysis, energy dispersive X-ray spectroscopy (EDS), diffuse reflectance, UV–Visible, and photoluminescence (PL) spectroscopies. The electronic structure of the Bi24O31Cl10 bulk material was analyzed using Density Functional Theory (DFT).Rietveld refinement confirmed the formation of a pure monoclinic Bi24O31Cl10 phase with the space group P2/c, and the XRD patterns indicated well-crystallized material. SEM revealed micron-sized crystallites, while BET surface area analysis showed a value of 22.546 m²/g, suggesting that a larger surface area could enhance photocatalytic performance. The band gap of the material was determined to be 2.88 eV, with an absorption edge at 430 nm, indicating a promising response to visible light.The photocatalytic activity of Bi24O31Cl10 was demonstrated by the degradation of rhodamine B (RhB), with complete degradation achieved in 90 min under UV light. Under visible light, 98 % degradation efficiency was reached after 180 min. Kinetic studies showed that the degradation followed a pseudo-first-order model. Optimal conditions for maximum degradation were found at a solution pH of 5, a catalyst concentration of 1 g/L, and a dye concentration of 5 mg/L. Remarkably, the photocatalyst exhibited excellent reusability, maintaining high efficiency over five cycles, with only a slight decrease from 100 % to 90 %.Trapping experiments identified that reactive species such as superoxide radicals (∙O2−) and hydroxyl radicals (∙OH) played key roles in the photocatalytic process. The possible reaction mechanism was proposed, and degradation products were monitored using liquid chromatography-mass spectrometry (LC-MS), allowing for the elucidation of the degradation pathways of RhB. Additionally, the photocatalyst's effectiveness was tested on Methyl Orange (MO) and Methylene Blue (MB), achieving nearly 100 % degradation for MO and 41 % for MB under UV light. This research highlights the significant potential of Bi24O31Cl10 as a photocatalyst for dye degradation in wastewater treatment.

Nanocrystalline transition metal tetraborides as efficient electrocatalysts for hydrogen evolution reaction at the large current density

While great efforts have been made to improve the electrocatalytic activity of existing materials toward hydrogen evolution reaction (HER), it is also importance for searching new type of nonprecious HER catalysts to realize the practical hydrogen evolution. Herein, we firstly report nanocrystalline transition metal tetraborides (TMB4, TM=W and Mo) as an efficient HER electrocatalyst has been synthesized by a single-step solid-state reaction. The optimized nanocrystalline WB4 exhibits an overpotential as low as 172 mV at 10 mA/cm2 and small Tafel slope of 63 mV/dec in 0.5 M H2SO4. Moreover, the nanocrystalline WB4 outperforms the commercial Pt/C at high current density region, confirming potential applications in industrially electrochemical water splitting. Theoretical study reveals that high intrinsic HER activity of WB4 is originated from its large work function that contributes to the weak hydrogen-adsorption energy. Therefore, this work provides new insights for development of robust nanocrystalline electrocatalysts for efficient HER.

Facile one-step solid-state synthesis of CuO nanoparticles finely decorated over carbon sheets for improved OER activity

Renewable energy storage and conversion in electrochemical fuel cells require highly efficient and cost-effective noble metal free electrocatalysts for oxygen evolution reaction (OER). Downscaling of a material to nanoscale morphology can lead to enhancement in its surface activities affecting its physical and chemical properties which can well serve the purpose. In lieu to this, it could be one of the first reports to tune the morphology of CuO particles to 10–25 nm finely trapped inside non-graphitic carbon sheets using a novel single step solid state reaction. XRD, SEM, TEM, XPS, and Raman analyses confirm the structural and morphological attributes. The synergistic effect from carbon and copper oxide resulted in the attainment of best-in-class electrode material for oxygen evolution reaction (OER). The as-prepared CuO/C shows an excellent OER activity with a low overpotential of 454 mV (vs. Ag/AgCl) at a current density of 10 mA cm−2 with a low Tafel slope of 74.9 mV dec−1. The amount of carbon is optimized to get optimal performance from the CuO nanopowder.

Coupled Ion-Conduction Mechanism for Enhanced Ionic Conductivity in Mg2B2O5 Nanowires Enabled Poly(ethylene oxide)-Based Quasi Solid State Electrolytes

Achieving room temperature high ionic conductivity of polymer solid state electrolytes equivalent to organic liquid electrolytes currently used in lithium ion batteries is a challenging task. The glass transition, crystallinity, free volume structure, salt dissociation, and ionic diffusion affect the ionic conductivity of polymer-based solid state electrolytes. In the present study, we report high-ionic conductivity (4.1 × 10–4 Scm–1) at room temperature for Mg2B2O5 nanowire-enabled solid state electrolytes of fully amorphous poly(ethylene oxide) (PEO). The Mg2B2O5 nanowires are synthesized using a single-step solid state reaction from inexpensive materials. The detailed investigation of the ion conduction mechanism using broadband dielectric spectroscopy confirms that the ionic conduction and segmental relaxations are a coupled phenomenon in these electrolytes, and segmental relaxation-mediated ionic diffusion is the primary ionic conduction mechanism. The enhancement in ionic conductivity on loading of Mg2B2O5 nanowires is attributed to the enhancement in the dissociated ionic concentration, ionic diffusion, and faster segmental relaxation due to interactions between the polymer, Li salt, and the nanowires. The smaller free volume size and enhanced free volume density of PEO in the electrolytes determined using positron annihilation lifetime spectroscopy and reduction in glass transition temperature determined from differential scanning calorimetry further confirm the role of modified chain packing and segmental relaxations in enhancement of ionic conductivity.

Validity of isothermal kinetic prediction by advanced isoconversional method

Isothermal prediction based on kinetic parameters from advanced isoconversional method (NLN) has been successfully used in various materials. However, the validity of the method is sometimes suspected because of some depressing predictions. In this paper, we set a single-step solid state reaction and a multi-step solid state reaction to simulate and predict. The effects of set temperature and composition of heating rate group on the isothermal prediction are evaluated. For the single-step reaction, all the relative errors of single-step reaction are less than 10%. Therefore, the method provides accurate enough isothermal predictions at different set temperatures and heating rate groups. As for the multi-step reaction, the accuracy of prediction varies with the set temperature and the composition of heating rate group. The reason for the failure of multi-step reaction prediction is the inconsistency in the concept of isothermal and nonisothermal isoconversional activation energy.

Enhanced electrochemical performance of LiVPO4F/C composite with in-situ generated Li3V2(PO4)3 for lithium-ion batteries

The vanadium-containing phosphate polyanion LiVPO4F has been attractive as a novel 4 V cathode for lithium-ion batteries. Herein, a hybrid cathode containing two active components of LiVPO4F and Li3V2(PO4)3 was successfully obtained by single-step solid-state reaction. The crystalline grains are coated by an amorphous carbon layer of about 8 nm thick. The composite presents reversible capacities of 102.8 and 98.2 mAh g−1 at the rates of 10C and 20C, respectively. Even at an ultrahigh rate of 100C (14.5 A g−1), it remains a discharge capacity of 70.1 mAh g−1 with a high average working potential of 3.5 V. After cycled 500 times at 10C, the obtained sample shows a capacity retention of 78.6%, implying outstanding cycling performance. The electrochemical impendence spectroscopy demonstrates that the hybrid cathode delivers higher lithium-ion diffusion coefficient. It is believed that the electrochemical performance is enhanced synergistically by the in-situ generated ionic conductor of Li3V2(PO4)3. Finally, when charged and discharged at around 4.1 V, the intermediate phase of LixVPO4F is clearly revealed by CV tests, which likely derives from a symmetry phase transform mechanism.

Electrical studies of Pb0.6Bi0.4Fe0.7Nb0.3O3 multiferroic

The multiferroic Pb0.6Bi0.4Fe0.7Nb0.3O3 was prepared using a single step solid state reaction technique. A comprehensive impedance spectroscopy technique was used to examine the dielectric, impedance, modulus and electrical conductivity of the sample. The dielectric constant of the sample was strongly affected by frequency and temperature. Temperature-dependent relaxation events in dielectric loss were seen in the material. With a non-Debye kind of relaxation process, the Nyquist plot shows the grains and grain boundary contribution to the conductivity. The bulk resistance reduces as the temperature rises and the temperature coefficient of resistance was found to be negative. The temperature-dependent relaxation processes with non-Debye type were shown in an electrical modulus study with increasing trend of AC conductivity with rise in temperature. Pb0.6Bi0.4Fe0.7Nb0.3O3 could be useful in multiferroic applications.

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

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

Impedance and modulus studies of Pb(Fe0.5Nb0.5)O3–Pb(Co0.33Nb0.67)O3 solid solutions

The high quality polycrystalline (1-x)Pb(Fe0.5Nb0.5)O3(PFN)–(x)Pb(Co0.33Nb0.67)O3(PCN) (abbreviated as PFCN) ceramic solid solutions (x = 0.1, 0.2, 0.3, 0.4 and 0.5) were synthesized via single-step solid-state reaction technique. The formation of a single-phase, monoclinic structure with Cm symmetry and without any secondary phase was confirmed through the room temperature (RT) X-ray diffraction (XRD). The microstructure of sintered ceramics with well-grown grains having average grain size of 1–2 µm were observed through scanning electron microscopy (SEM). To understand the electrical response of the material impedance and modulus spectroscopy studies were carried out. A detailed temperature (301–481 K) and frequency (100 Hz to 6 MHz) dependent impedance and modulus of PFCN ceramic solid solutions were reported. The impedance spectroscopy reveals the increase of conductivity in the system by the addition of Pb(Co0.33Nb0.67)O3 due to increased number of oxygen vacancies (OVs)/defects created at the grain boundary interface during the synthesis. The Z′ vs. frequency shows the creation of space charges by the participating ionized OVs in the conduction process and Z′′ vs. frequency shows the presence of temperature-dependent relaxation processes in the PFCN solid solutions. The Nyquist plot (Z′′ vs Z′) shows the depressed semicircles suggesting the deviation from Debye type of relaxation behaviour and a decrease in the grain resistance for all compositions with rise in temperature, correlates the NTCR (negative temperature coefficient of resistance) nature. The M′ vs. frequency display the step-like behavior due to dipole contribution to the modulus present in the grain and grain boundary region. Fitted Kohlrausch-Williams-Watts (KWW) function to M′′ vs. frequency demonstrates the non-Debye type relaxation behavior in the PFCN solid solutions. The mismatch of fmax in the Z′′, M′′ vs. frequency indicates the short-range mobility of localized charge carriers.

Enhanced photodetector performance in gold nanoparticle decorated ZnO microrods

Herein, we present a facile synthesis of ZnO microrods and surface decoration with gold nanoparticles using a low-cost deposition apparatus. The ZnO microrods were fabricated via a single-step solid-state reaction, and the gold nanoparticles were synthesized on the surface of the microrods by the deposition of gold thin films and sequential heat treatment. The size of the gold nanoparticles was controlled by varying the thickness of the gold thin films and the annealing temperature. The intensity of green emission in the photoluminescence spectra decreased with increasing gold nanoparticle size. A surface plasmon resonance peak originating from the gold nanoparticles appeared at ~570 nm in the absorption spectra, and the peak redshifted as the nanoparticle size increased. The ultraviolet (UV) on–off current ratio and response speed of single ZnO microrod photodetectors significantly increased after surface decoration by gold nanoparticles. However, the performance of the photodetector degraded as the size of the gold nanoparticles increased owing to the absorption of incident UV light. The enhanced photodetector performance of the surface-modified ZnO microrods is explained by the transfer of energetic electrons excited by surface plasmon resonance from the defect level to the conduction band of the ZnO microrods.

Investigation of the physical properties of (Cu0.5Tl0.5)Ba2Ca2Cu3O10-δ impregnated with mono cobalt(II)-substituted Undecatungstosilicate Nanoparticles

A series of (Cu0.5Tl0.5)Ba2Ca2Cu3O10-δ superconducting samples impregnated with different percentage additions of potassium salt {CoSiW11}x nanoparticles (x = 0.00, 0.01, 0.02, 0.04, 0.06, 0.08 and 0.12 wt.%) were prepared using a single-step solid-state reaction technique at ambient pressure. These samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) to study their structures, construction of the synthesized samples and elemental composition, respectively. XRD studies indicate that the tetragonal structure of (Cu0.5Tl0.5)-1223 phase has not changed by the addition of {CoSiW11} nanoparticles the same as for the values of lattice parameters a and c, where they show a non-remarkable change. The relative volume fraction of (CuTl)-1223 phase record a maximum value for x = 0.02 wt.%. The formation of (CuTl)-1223 phase matches the presence of rectangular-shaped plates seen in SEM images. The enhancement of these plates after the addition of {CoSiW11} nanoparticles up to x = 0.02 wt.% agreed with the measurements of relative volume fraction. The mass percentage of all elements was measured using the EDX technique, which shows the distribution composition of both superconductor and nanoparticle compounds. Vibrational mode analyses of oxygen were accomplished via Fourier transform infrared (FTIR) spectroscopy in (CuTl)-1223 phase impregnated with {CoSiW11} nanoparticles. The Oδ oxygen modes observed are almost unaltered while the other oxygen modes of planar CuO2 are slightly softened and hardened. Superconducting transition temperature (Tc) and critical current density (Jc) were determined from the electrical resistivity and I–V measurements, respectively. The results indicate an increase in the Tc values from 125 K for the pure sample to 132 K for x = 0.02 wt.% impregnated samples, while a decrease in the Jc values is observed upon increasing ‘x’ value from x = 0.00 up to 0.12 wt.%. The suppression of these electrical superconducting parameters for x > 0.02 wt.% may be due to an increase of weak links' connectivity among the grain boundaries and growth of impurity phases that affect the formation of (CuTl)-1223 superconductor phase. The fluctuation-induced conductivity (FIC) analysis has been done in the light of the Aslamasov–Larkin (AL) theory to study the fluctuation conductivity Δσ above Tc as a function of reduced temperature for (CoSiW11)x/(CuTl)-1223 superconductor. The results show four non-identical fluctuation regions that are short-wave (Sw), two-dimensional (2D), three-dimensional (3D) and critical (Cr). The zero-temperature coherence length ( $${\xi }_{c}(0)$$ ), the effective layer thickness of the two-dimensional system (d), inter-layer coupling (I), Fermi velocity (vF) and Fermi energy (EF) were evaluated as a function of ‘x’ addition from FIC analysis of the samples and then correlated to the superconductivity order parameters. The superconducting parameters were increased upon the addition of {CoSiW11} nanoparticles.

Facile synthesis of ZnO microrod photodetectors by solid-state reaction

In this study, ZnO microrods were directly synthesized via a single-step solid-state reaction using ZnO powders mixed with graphite without a catalyst under an air atmosphere, instead of using vacuum systems and flowing gases. The structure, growth mechanism, and electrical and optical properties of the microrods were investigated under varying growth conditions. The high-resolution transmission electron microscopy images confirmed the formation of single-crystal ZnO microrods. The photoluminescence spectra of the microrods showed green emission, suggesting the formation of non-stoichiometric ZnO microrods due to the formation of oxygen vacancies during sintering. The length and width of the ZnO microrods could be modulated by controlling the graphite content, sintering temperature, and residual time. A simple photodetector consisting of a single-crystal ZnO microrod on a SiO2-coated Si substrate was fabricated. The photodetector exhibited a linear current–voltage curve in visible light. The slope of the curve increased under ultraviolet (UV) irradiation, maintaining a linear shape of the curve. The curve reversibly returned to the initial shape in the absence of UV illumination. The UV on-off current ratio increased because of the decrease in the off-current by compensating for the oxygen vacancies through annealing in an oxygen atmosphere. Thus, in this study, we proposed a simple and efficient approach to fabricate single-crystal ZnO microrods for application in low-cost photodetectors.

Single-step solid-state synthesis and characterization of Li4Ti5−xFexO12−y (0 ≤ x ≤ 0.1) as an anode for lithium-ion batteries

Li4Ti5−xFexO12−y (0 ≤ x ≤ 0.1) anode material was synthesized via a single-step solid-state reaction under a N2 atmosphere. The overdischarge behaviours and discharge mechanism of anode material at a lower voltage (0 V) was investigated.

Effect of electric poling on structural, magnetic and ferroelectric properties of 0.8PbFe0.5Nb0.5O3-0.2BiFeO3 multiferroic solid solution

The effect of electric poling on structure, magnetic and ferroelectric properties of 0.8PbFe 0.5 Nb 0.5 O 3 -0.2BiFeO 3 (0.8PFN-0.2BFO) multiferroic was studied through XRD, Raman, magnetic and ferroelectric measurements. Single step solid state reaction method was adopted to synthesize single phase 0.8PFN-0.2BFO multiferroic at lower calcination and sintering temperature. Room temperature (RT) XRD pattern before and after poling confirmed the monoclinic structure with Cm space group. Rietveld refined XRD for poled and unpoled sample shows the influence of electric poling on Fe-O1, Fe-O2, Nb-O and Bi-O modes. There is a small variation in the lattice parameters after electric poling. The structural properties were also studied in detail for the poled and unpoled 0.8PFN-0.2BFO using Raman spectroscopy. Raman measurements were carried out over a wide range of temperature (250–550 K) for both poled and unpoled samples. At RT unpoled 0.8PFN-0.2BFO multiferroic exhibit 8 active modes at 211, 263, 440, 484, 571, 706, 785 and 1120 cm -1 in the frequency range 100–1200 cm -1 . The Raman peaks exhibits significant changes in intensity as well as shape of the spectra at the characteristic temperature T C (470 K) and T N (310 K). Poled Raman spectra show major changes in the Fe/Nb-O modes intensities around T N and are due to dynamic nature of spin phonon coupling. Changes observed in the temperature dependent magnetic measurements i.e. ZFC/FC and M − H loop evidence the existence of converse magneto-electric coupling (CME) and this is due to the poling effects on Fe-O, Nb-O active modes. Due to rotation of the oxygen octahedral the electric field induced strain will originate in the system. P-E loops after poling show an increase in remnant polarisation and coercive field due to an improvement in domain ordering. The potential tunability of magnetisation with electric poling is an ideal tool for realisation of application in practical devices.

Magnetic Characterization of Bulk C-Added MgB2

To find a cheap and efficient way to produce high-performance bulk MgB2 superconductors, a series of samples produced with different contents of carbon-coated, nanometer-sized amorphous boron was prepared to improve the magnetic properties. A single-step solid-state reaction at the optimal reaction temperature of 805 °C for 3 h in pure argon atmosphere was used. Small pieces cut from the bulk were characterized by magnetic hysteresis loop measurements in magnetic fields up to ±7 T at temperatures ranging from 5 to 35 K using a physical property measurement system. Critical current densities and flux pinning forces were calculated from the magnetization data. The pinning force data of all samples were compared using the pinning force scaling approach by Eisterer. The peak positions h 0 were found at h 0 ∼ 0.33, indicating a dominant flux pinning at the grain boundaries for samples with 50% and 30% carbon-coated boron, while the scaling reveals a peak position of 0.44 for the 10% sample that indicates pinning at point defects.

Enhanced electron-phonon coupling in NbB2 by nanoscaling the grain size

Nanocrystalline NbB2 powder has been synthesized via a single step solid-state reaction of precursor materials Nb2O5 and NaBH4. Phase composition, grain morphology, microstructure, phonon vibrations and superconducting properties were investigated by XRD, FESEM, HRTEM, Raman spectroscopy and PPMS. The results show that the grain size of nanocrystalline NbB2 is very sensitive to the reaction temperature and easy to aggregate to form micron scale of non-morphology powders. A systematic increase of the electron-phonon coupling constant with the nanoscaling grain size is observed, which we explain in terms of crystal defects and phonon vibrations. The zero-temperature critical fields, Hc1 (0) and Hc2 (0), have been estimated at 85 Oe and 7200 Oe, respectively, and the Ginzburg–Landau parameter κ is 5.1, confirming that NbB2 is a type-II superconductor.

Synthesis, structural and lithium storage studies of graphene-LiVSi2O6 composites

Clinopyroxene LiVSi2O6 phase has been synthesised in this study by a single step solid state reaction in argon atmosphere at 900 °C, and its electrochemical properties have been investigated. Graphene composite of the material has also been prepared by assimilating GO (graphene oxide) to the reactants which gets reduced in situ to rGO (reduced graphene oxide) during the annealing process. Structure and morphology of the samples have been characterised by powder X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and surface area (BET) measurements. Lithium storage properties of the material were examined using galvanostatic cycling, cyclic voltammetry and electrochemical impedance spectroscopy studies. The rGO composite shows better capacity retention than the pristine sample, and an initial discharge capacity of 110 mAh g−1 was obtained for the rGO composite.

Flux Pinning and Superconducting Properties of MgB2-Diamond Nanocomposites

The present investigation focuses on a further performance improvement of disk-shaped bulk MgB2 superconductors by means of a nanoscopic diamond powder, using a single-step solid-state reaction process. MgB2 bulks were produced by in-situ solid state reaction in Ar gas using high purity commercial powders of Mg metal and amorphous B mixed in a fixed ratio of Mg:B = 1:2. Further, 0, 0.4, 0.8, and 1.2 wt% of nanoscopic diamond powder was added to improve flux pinning performance of the bulk MgB2 material. All samples were sintered at 775 °C for 3 hours in Ar atmosphere. X-ray diffraction confirmed that the sample consisted mainly of MgB2 phase and a small quantity of MgO phase. DC magnetization measurements showed a sharp superconducting transition with onset Tc at around 39.25 K and 37.42 K for the pure and 0.8 wt.% of nanoscopic diamond powder added samples, respectively. The highest self-field critical current density (Jc) around 300 kA/cm2 and 105 kA/cm2 were recorded at 20 K, in self-field and 1.5 T for the sample with 0.8 wt.% of nanoscopic diamond. The present results show that nanoscopic diamond powder is an effective pinning medium for bulk MgB2 and might thus be an alternative to further improve the superconducting performance of the bulk MgB2 material.

Enhanced Critical Current Density in Bulk MgB2

The object of this investigation is to improve the flux pinning and critical current density (J c ) of bulk MgB 2 materials for daily applications including superconducting permanent magnets. We prepared two sets of bulk MgB 2 materials employing commercial high-purity powders of Mg metal and carbon-coated amorphous B using a single-step solid-state reaction process. The first set of samples was produced by a single-step solid-state reaction at various temperatures between 794 °C and 806 °C in steps of 3 °C in pure argon atmosphere to optimize the sintering temperature. Further, the second set of samples was produced from Mg-rich MgB 2 material adding 1.5 wt% carbon-coated amorphous B powder to it, combined with 4 wt% of silver. X-ray diffraction analysis showed that samples were single-phase MgB 2 with minor trace of impurities. In all samples, sharp superconducting transition temperatures were observed around 38 K, which was decreased around 1 K in MgB 2 material produced with 1.5 wt% of carbon encapsulated boron. The critical current densities in Mg-rich MgB 2 material with 4 wt% of Ag were lower than in silver-free MgB 2 bulks. The sample with 1.5 wt% of carbon-coated B exhibited the highest J c of 460 kA/cm 2 at 20 K and self-field. Our results demonstrate a strong correlation between the microstructure achieved and the resulting pinning performance.

Low Temperature Dielectric and Impedance Spectroscopy Studies of 0.9PFN - 0.1BFO Multiferroic Solid Solution

Single step solid state reaction method was adopted to synthesize 0.9PFN - 0.1BFO (PFN - BFO) multiferroic solid solution. Single phase was confirmed through X-Ray Diffraction (XRD) and the structural analysis from Rietveld refinement confirms the monoclinic structure with Cm space group. Temperature dependent dielectric constant and loss tangent shows an anomaly around Néel temperature (TN) at 240 K and is a clear signature of existence of indirect magnetoelectric coupling in the solid solution. The complex impedance spectroscopy exhibits a significant contribution from the grains and confirms the non Debye type nature. Bulk resistance decreases with increase in temperature shows negative temperature coefficient of resistance (NTCR) behavior. Electrical modulus spectra are of non Debye type. The ac and dc conductivity of the materials were found to increase with increase in temperature.