Standard Solid State Reaction Route Research Articles

Impact of hair-derived carbon substitution on structural and superconducting properties of MgB2

This study presents a comprehensive analysis of the effects resulting from the substitution of biowaste-derived carbon-dot (CD) from human hair on structural and superconducting properties of MgB2. Syntheses of polycrystalline samples were accomplished through a standard solid-state reaction route. X-ray powder diffraction results confirm the formation of MgB2 as a primary phase in all samples and show the successful substitution of carbon for boron in MgB2. The critical current density, determined at 20 K and 4.5 T, for carbon-substituted MgB2 synthesized at 850 °C was enhanced by more than four times compared with unsubstituted MgB2. The observed improvement is due to the formation of efficient pinning centers resulting from the incorporation of carbon substituting for boron in MgB2. Furthermore, x-ray photoelectron spectroscopy (XPS) confirmed the presence of carbon bonding to boron in MgB2 synthesized with biowaste-derived CDs, indicating successful incorporation into the structure. Ultraviolet photoelectron spectroscopy (UPS) results show that the carbon-substituted MgB2 can lead to changes in the electronic band structure and values of work function. These changes significantly impact the properties of MgB2 materials, including superconducting transition temperature, upper critical field, and critical current density. The XPS and UPS experimental results are in good agreement with density functional theory calculations for MgB2 with and without carbon substitution.

Effect of Ce4+→Ce3+ conversion on the structural and luminescence properties of Ce4+ doped Gd2Ti2O7 pyrochlore oxide

Ternary oxides with cerium oxide as dopant are now useful as blue chip for the production of WLED's. In this present work, pyrochlore oxides Gd2Ti2-xCexO7 with doping concentration x = 0, 0.04, 0.08, 0.12, and 0.16, were prepared through standard solid-state reaction route. A pyrochlore structured phase is formed in the synthesized series as confirmed by conventional techniques; i.e., X-ray diffraction and Raman spectroscopy. Both techniques were revealed a systematic unit cell expansion as a function of doping concentration. The SEM micrograph confirms the formation of spherically agglomerated micron sized grains. In the later section of the manuscript, Ce4+→Ce3+ conversion effect on structural and luminescent properties were investigated. A relatively larger amount of cell expansion and accumulation of the strain is observed in the pyrochlore structured reduced samples. X-ray photoelectron spectroscopic (XPS) was used to investigate the oxidation state of the Gd, and Ti cations and oxygen anion. PL excitation spectra showed two broad bands centered around 255 nm and 360 nm due to the 4f→5d transition of Ce3+ ions at λem = 425 nm. Moreover, PL emission spectrum shows a broad peak around 425 nm at λex = 360 nm due to the 5d to 2F7/2 and 2F5/2 transitions. We observed that for the Ce4+→Ce3+ conversion both the PL emission and excitation spectra give far better results as compared to unreduced samples. Concentration quenching effect was observed for the doping concentration of 4% of cerium dopant. For 4% doping of cerium ion, CIE chromaticity results showed that the reduced as well as unreduced samples produce a bright blue colored emission line. The present study provides an insight about the potential use of Ce4+→Ce3+: Gd2Ti2O7 to synthesize blue LED chips for the fabrication of WLED's.

Observation of Enhanced Unipolar Strain and Piezoelectric Charge Co-Efficient in K0.5Na0.5NbO3 Simultaneously Doped with Lithium and Antimony

The author reports an enhanced strain and piezoelectric charge coefficient (d33*) in lead-free Lix(K0.5Na0.5)1−x(Nb1−ySby)O3 (x and y = 0,0.02,0.04,0.06) ceramics synthesized through the standard solid-state reaction route. X-ray diffraction analysis of the samples predicts a structural phase transition from orthorhombic to tetragonal with the presence of phase boundary (coexistence of orthorhombic and tetragonal phases) for the Li0.04(K0.5Na0.5)0.96(Nb0.96Sb0.04)O3 sample supported by Raman spectroscopy. The Lix(K0.5Na0.5)1−x(Nb1−ySby)O3 (x and y = 0.04) ceramics exhibited enhanced electrical properties with Ps∼13 µC/cm2, Ec∼15 kV/cm, an electrostrictive strain of 0.38% and piezoelectric charge coefficient (d33*) of 950 pm/V, making it promising for sensor and actuator applications.

Phase boundary and temperature driven enhanced piezoelectric and electrostrictive strain in (1−2x) Bi0.5Na0.5TiO3-xBaTiO3-xBa0.7Ca0.3TiO3 solid solution

Bismuth-based piezoelectric ceramics are presently of immense interest to researchers as they are believed to be Pb-free alternatives to well-known lead zirconate titanate-based piezoceramics. Herein, the author reports a lead-free ternary solid solution (1−2x)Na0.5Bi0.5TiO3-xBaTiO3-xBa0.7Ca0.3TiO3 (x = 0.01, 0.03, 0.05, 0.07, and 0.09: BNT-BT-BCT) synthesized through a standard solid state reaction route. All the samples crystallized to a complete perovskite structure studied through the powder x-ray diffraction analysis. Rietveld analysis of x-ray diffraction data revealed a structural transformation from monoclinic (Cc) to tetragonal phase (p4mm) with the co-existence of monoclinic (Cc) and tetragonal (p4mm) phases in the samples of x ≥ 0.03. The temperature-dependent dielectric analysis of (x = 0.03 and x = 0.05) systems suggests relaxor characteristics near ferroelectric–antiferroelectric phase transition temperature (Td). A changeover from relaxor to a near normal ferroelectric character was realized for x ≥ 0.07. Furthermore, the existence of polar nano-regions (PNRs) was studied through HR-TEM. Interestingly, a low electric field (±25 kV/cm) driven enhanced piezoelectric [(with 0.22% of strain; Smax/Emax = 850 pm/V for x = 0.03) and (with 0.17% strain and Smax/Emax of 714 pm/V for x = 0.07)] and an electrostrictive [with 0.20% of strain; Smax/Emax = 820 pm/V for x = 0.05] was achieved around Td. This can be attributed to the combined effects of phase boundary, ferroelectric–antiferroelectric transition, and the existence of PNRs.

Room Temperature Synthesis of Colossal Magneto-Resistance of La2/3Ca1/3MnO3: Ag0.10 Composite

Rare-earth manganite-based perovskite has great potential as a promising material for spintronics and ferroelectromagnets. Herein, we have synthesized La2/3Ca1/3MnO3:Silverx (LCMO-Agx; where x = 0.00 and 0.10) composite using a standard solid-state reaction route. Their structural and physical properties have been investigated. Pristine LCMO and LCMO-Ag composite are crystallized in an orthorhombic structure, which is in a single-phase and has a space group of Pbnm. Pristine LCMO and LCMO-Ag composite’s structural analysis showed better grain connectivity in ferromagnetic domains of LCMO-Ag composite compared to pristine LCMO. Ag doping enhances the paramagnetic-ferromagnetic transition Tc (Curie temperature) to 277 K, which is 8 K higher than that of pristine LCMO (Tc = 269 K). Additionally, the magneto-resistance (MR) of LCMO-Ag composite was improved by ∼10% with Ag doping even at room temperature (RT), which is due to improved connectivity and grain size with Ag doping. Thus, the enhanced value of MR at RT may efficiently open up the possible use of LCMO-Ag composite as ferroelectromagnets and spintronics applications. Additionally, LCMO thin films can be useful in artificial planar junctions, vertical tunnel junctions, and sensing applications.

Electronic structures and magnetic studies of SmFeO3 thin films and powders

In this work, the electronic structures and magnetic performance of SmFeO3 (SFO) powders prepared by standard solid-state reaction route and thin films fabricated by pulsed laser deposition (PLD) on SrTiO3 (STO) (100) substrates were investigated.The X-ray diffraction (XRD) investigations prove the phase purity of both SmFeO3 powders and thin films. X-ray photoelectron spectroscopy (XPS) was employed to study the chemical composition and the valence states of elements. With the purpose of studying the electronic structure of SFO samples, especially the orbital hybridization in the samples, X-ray absorption Spectroscopy (XAS)were also accomplished. Remarkably, we observed the difference in XAS of OK-edgeand FeL-edge between SmFeO3 powders and thin films. It was observed that the samples exhibited different exchange bias effect (EB) from magnetization investigations, which were probably dependent on the changes of the orbital hybridization and bond length of the samples.

Structural, thermal stability and electrical conductivity of zirconium substituted barium cerate ceramics

Barium cerate perovskite ceramics substituted with zirconium BaCe1-xZrxO3 (x = 0, 0.05, 0.10, 0.15, 0.20) were prepared by the standard solid-state reaction route. The x-ray diffraction patterns affirmed the single-phase orthorhombic symmetry of the synthesized ceramics. The thermal stability of the samples has been checked by thermogravimetric analysis (TGA). TGA of dry and pre-hydrated (pH2O (g) ≈ 0.03 atm and 1.0 atm) compositions revealed that all the samples are stable up to a temperature of 800 °C. However, the samples treated at a higher partial pressure of water are found less stable. The crystalline phase of the studied compositions before and after TGA was measured with the Raman study, confirming that most of the parent phases exist or remain stable even after the treatment of samples at higher vapor pressure. Thermal stability gradually improved with increasing Zr-substitution. The TGA results that are consistent with the Raman studies proved the sample with x = 0.20 is the most stable among the studied compositions. Complex impedance spectroscopy studies clearly demonstrated the impact of bulk and grain boundary on the total resistance of the compounds with different zirconium contents. The Arrhenius dependence of the total conductivity indicates that the conductivity decreased with an increase in Zr concentration both in air and wet nitrogen atmosphere. Comparing the conductivity under both ambiances suggests that some additional charged species participate in the conduction mechanism under the wet environment. These are ascribed to the protonic defects, developing into barium cerate via extrinsic oxygen vacancies because of high-temperature sintering.

Defect induced room temperature ferromagnetism in high quality Co-doped ZnO bulk samples

The nature of the often reported room temperature ferromagnetism in transition metal doped oxides is still a matter of huge debate. Herein we report on room temperature ferromagnetism in high quality Co-doped ZnO (Zn1−xCoxO) bulk samples synthesized via standard solid-state reaction route. Reference paramagnetic Co-doped ZnO samples with low level of structural defects are subjected to heat treatments in a reductive atmosphere in order to introduce defects in the samples in a controlled way. A detailed structural analysis is carried out in order to characterize the induced defects and their concentration. The magnetometry revealed the coexistence of a paramagnetic and a ferromagnetic phase at room temperature in straight correlation with the structural properties. The saturation magnetization is found to increase with the intensification of the heat treatment, and, therefore, with the increase of the density of induced defects. The magnetic behavior is fully explained in terms of the bound magnetic polaron model. Based on the experimental findings, supported by theoretical calculations, we attribute the origin of the observed defect-induced-ferromagnetism to the ferromagnetic coupling between the Co ions mediated by magnetic polarons due to zinc interstitial defects.

Studies of structural and electrical properties of (Pb0.9Bi0.05Dy0.05)(Fe0.1Ti0.9)O3 ceramic

In this communication, detailed studies of structural, dielectric, and electrical characteristics of dysprosium (Dy)-modified bismuth ferrite–lead titanate (BiFeO3–PbTiO3) solid solution, [i.e., (Pb0.9Bi0.05Dy0.05)(Fe0.1Ti0.9)O3)], prepared by a standard high-temperature solid-state reaction route, have been reported. From the preliminary X-ray structural analysis with Rietveld refinement method, the structure of the material is found to be tetragonal. Detailed analysis of surface morphology, X-ray energy-dispersive spectra and elemental mapping has shown uniform distributions of grains of varying size and elemental composition of the compound. The frequency dependence of the dielectric constant has been explained by the Maxwell–Wagner model. As both the components of the solid solution (BiFeO3 and PbTiO3) have high-temperature ferroelectric transition, no dielectric anomaly has been observed in the said experimental range of our temperature dependence of dielectric studies. The detailed analysis of Nyquist plots, using impedance data collected in a wide range of frequency and temperature shows the contributions of both grains and grain boundaries in the resistive and capacitive characteristics of the prepared material. Both negative and positive temperature coefficients of resistance behaviour are observed in the material. The frequency and temperature dependence of ac conductivity obeys Jonscher’s power law and Arrhenius equation. The occurrence of electric field dependence (P–E) hysteresis loop at room temperature shows the ferroelectric property of the material.

Composition-dependent structural, electrical, magnetic and magnetoelectric properties of (1 − x)BaTiO3−xCoFe2O4 particulate composites

Multiferroic composite with the general formula (1 − x)BaTiO3−xCoFe2O4 (x = 0.05, 0.15, 0.25, 0.35 and 0.45) has been synthesized by a standard solid-state reaction route. Powder X-ray diffraction analysis confirms the existence of ferrite (spinel CoFe2O4) and ferroelectric (tetragonal BaTiO3) biphase without any impurity phases in the sintered composites. Microstructure of the composite displays two different grain sizes and shapes studied from SEM analysis. The composites show both ferroelectric and ferromagnetic ordering: the saturation magnetization (Ms) and retentivity (Mr) of the composite are improved with the increase in ferrite phase, while leakage current, ferroelectric and dielectric properties of the composites show a drop. Existence of coupling between ferroelectric and ferromagnetic ordering measured through magnetodielectric (MD) and magnetoelectric (ME) studies reveal an increase in % MD and ME coefficients with an increase in ferrite content. An enhanced ME coupling coefficient of 17 mV cm−1 Oe−1 has been realized at a dc magnetic field of 5 kOe with a ac frequency of 50 Hz in (1 − x)BaTiO3−xCoFe2O4 (x = 0.45) composite.

Observation of enhanced electrostrictive strain in (1-2x)Na0.5Bi0.5TiO3-xBaTiO3-xBiAlO3 lead-free ceramics

Herein, the author reports the observation of composition dependent piezoelectric and electrostrictive behaviour in lead free (1-2x)Na0.5Bi0.5TiO3-xBaTiO3-xBiAlO3: NBT-BT-BAO [x = 0.01, 0.03, 0.05, 0.07, 0.09] ceramics synthesized through standard solid state reaction route. X-ray diffraction analysis of the samples confirms existence of structural phase transition from monoclinic to pseudocubic with increase of BT and BAO concentration supported by Raman spectroscopic analysis. A flipping from piezoelectric (x≤ 0.03) to near-electrostrictive (x≥ 0.05) characteristics has been realized from strain vs electric field measurements. Especially, (1-2x)Na0.5Bi0.5TiO3-xBaTiO3-xBiAlO3: x = 0.05 showed an enhanced strain of 0.33 %, Smax/Emax of 425 pm/V and an electrostrictive co-efficient (Q33) of 0.034 m4C−2 could be attributed to the presence of MPB by the co-existence of monoclinic and pseudocubic phases. Further, minimal temperature dependence of the electrostrictive strain is inferred from temperature dependent polarization and strain measurements.

Crystal structure, spectra analysis and dielectric characteristics of Ba4M28/3Ti18O54 (M= La, Pr, Nd, and Sm) microwave ceramics

High dielectric constant Ba4M28/3Ti18O54 (M = La, Pr, Nd, and Sm) ceramics were synthesized via standard solid-state reaction route. All the samples possessed single-phase orthorhombic tungsten-bronze structure, and the unit cell volumes decreased monotonously when rare-earth ion changed from La to Sm. With the decreasing radius of rare-earth ions, the dielectric constant (εr) gradually decreased, which was correlated with the decrease of total ionic polarizability and blue shift of Raman vibration modes. The increase of the quality factor (Q × f) was associated with the increase of packing fraction and the decrease of FWHM of Raman vibration modes (Ag and B1g). The temperature coefficient of resonant frequency (TCF) shifted in the negative direction, which was highly related to the decrease of the TiO6 octahedral tilt angle. Infrared reflection (IR) spectroscopy analysis indicated that the infrared vibration modes between TiO6 octahedron and A-site cation (M3+ and Ba2+) at low frequency dominated microwave dielectric polarization in the Ba4M28/3Ti18O54 ceramics.

Effect of Co/Cu partial replacement on fundamental features of Y-123 ceramics

This study is liable for the effect of sample production processes including the standard solid-state reaction (SSR) and classical sol–gel (SG) preparation methods on the fundamental characteristic features, namely electrical, superconducting, crystal structure quality, crystallinity, morphological, strength quality of grain boundary couplings, and interaction between the grains of YBa2Cu3−xCoxO7−δ (Y-123) advanced ceramic compounds within the weight ratio intervals x = 0–20%. The main heat treatments are exerted at two main steps: (I) annealing at 950 °C for 24 h in air medium conditions and (II) annealing at 500 °C during 5 h under the oxygen annealing ambient. The standard measurement methods such as powder X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, temperature-dependent electrical resistance, and Vickers hardness measurements are performed for the characterization of materials. It is found that the samples prepared at SSR route present much more superior characteristic features as compared to those fabricated at SG technique, being one of the most striking points deduced this work. In more detail, every material prepared crystallizes in the orthorhombic symmetry and exhibits the superconducting nature but considerable decrement in the critical transition temperatures. The onset and offset transition temperatures are noted to decrease regularly from 92.96 K (92.28 K) to 90.20 K (83.59 K); and 90.05 K (90.03 K) to 45.97 K (30.49 K) for the materials prepared by the SSR (SG) route. Similarly, the variation in the lattice cell and average grain size parameters confirm that the Co/Cu substitution damages Y-123 superconducting phase. Additionally, the Co/Cu partial replacement mechanism leads to increase significantly the Vickers hardness results. To sum up, the Co/Cu partial substitution (produced by either SSR or SG method) is plowed to improve the fundamental characteristic features for new, novel, and feasible market application areas of Y-123 cuprate ceramics in the universe economy.

Strengthened magnetoelectric multiferroic response in (K0.5Na0.5[Nb1-xFex/2Mnx/2]O3) ceramics

A new magnetoelectric multiferroic K0.5Na0.5 [Nb1-xFex/2Mnx/2]O3 (x = 0.025, 0.05, 0.075, 0.10) ceramics is synthesized successfully using standard solid-state reaction route. Powder X-ray diffraction (PXRD) patterns of all the compositions show characteristic orthorhombic doublet reflections of pure KNN which further confirms no substitution assisted structural changes to exist. Single-phase crystallization of the compounds with no existence of acceptor dopants in the form of metal/oxide clusters is also confirmed through selected area electron diffraction (SAED) patterns. The multiferroic nature of the synthesized compounds, the coupling between electrical and magnetic ordering is studied. A longitudinal magnetoelectric (ME) coefficient (L-αME) value of 3.45 mV/cm.Oe is achieved for K0.5Na0.5[Nb1-xFex/2Mnx/2]O3 (x = 0.05).

Graphene oxide modified superconducting and elastic parameters of YBCO superconductor

In the present work, (1-x) YBa2Cu3O7-δ + x Graphene Oxide (GO) {x = 0.0, 0.2, 0.4, 0.6 and 0.8 wt %} composite samples were prepared by standard solid state reaction route. The phase purity, structural and morphological analyses of the composite samples were observed through the X-ray powder diffraction and Field emission scanning electron microscopy respectively. The variations of superconducting parameters were observed through the resistivity vs. temperature and electric field vs. current density measurement. The onset of the superconducting transition temperature (TCon) enhances with increasing wt. % of graphene oxide and the maximum value was found to be 97.02 K for 0.8 wt % graphene oxide added YBCO sample. This may be attributed to the improved inter-linking among the superconducting grains and enhancing the transport of carrier density between the inter-granular sites. As a consequence of the superconducting volume fraction of the composite samples increases, hence critical current density is enhanced with increasing wt. % of graphene oxide. The Ultrasonic measurement has been utilized to observe the elastic parameters of the composite materials.

Structural, dielectric and electrical characteristics of manganese modified Bi0.5K0.5TiO3 ceramic

The manganese modified Bi0.5K0.5TiO3 ceramic (i.e., Bi0.5K0.5Ti0.80Mn0.20O3) was synthesized by a standard solid-state reaction route. Rietveld refinement of X-ray diffraction data confirms that the compound crystallizes in the tetragonal symmetry with P4bm space group. The substitution of 20% Mn ions at the Ti-sites results in a substantial increase in the dielectric constant and a decrease in the dielectric loss in the compound making the material attractive for high-frequency device applications. The analysis of complex impedance and modulus spectroscopy confirms the non-Debye type of relaxation mechanisms in the material with contribution from both the grain and grain boundary to the electrical properties. The AC conductivity data are analyzed to determine the activation energy of the charge carriers participating in the conduction process and to predict the dominant conduction mechanism in the sample.

Temperature-dependent transport properties of a FeTe compound

Temperature-dependent transport properties of a FeTe parent compound have been investigated by measurements of electrical resistivity \(\rho (T)\), thermal conductivity \(\kappa (T)\) and Seebeck coefficient S(T). The sample was synthesized using a standard solid state reaction route via vacuum encapsulation and characterized by X-ray diffraction spectroscopy, which indicated a tetragonal phase with the space group \(P4/{ nmm}\). The resistivity measurement data of the parent FeTe compound do not exhibit superconductivity however, it shows an anomaly in the temperature-dependent resistivity at around 67 K, which corresponds to structural phase transition in the vicinity of a magnetic phase transition. In the low temperature regime, Seebeck coefficient, S(T), exhibited an anomalous dip feature and negative throughout the temperature range, indicating an electron-like, single band charge carrier mechanism. We have also estimated the power factor and thermoelectric figure of merit ZT, which is found to be significantly smaller than other compositions of iron chalcogenides.

Structural and electrical properties of copper doped lanthanum manganite NPs

This paper reports on the structural and electrical properties of copper doped lanthanum manganite nanoparticles (NPs). The investigated samples were prepared via a standard solid state reaction route using the planetary ball milling technique. The X-ray diffraction patterns confirm their crystallinity and formation of single phase perovskite structure. The micrographs of field emission scanning electron microscopy shows the particles of almost non-spherical shape and a little agglomerated. The average particle sizes’ are in the nanorange. The energy dispersive spectroscopy marks the presence of the compositional constituents. A second order magnetic phase transition from paramagnetic to diamagnetic is observed from the dispersion of dielectric constant. The peaks are found in the loss tanδ spectra that correspond to energy loss as heat radiation. The higher energy loss as heat radiation is obtained for the composition with Cu content (x) = 0.2 and is assumed it to be more suitable in the dielectric heating as well as heat generating applications. The peaks are observed at around 10 kHz in their M″ spectra, which indicate the transition from short-range to long-range mobility of ions. However, the peak position in the dispersion of M′ are detected to shift rightward with the Cu content (x).

Crystal and Magnetic Structures of Melilite-Type Ba2MnSi2O7.

Melilite-type Ba2MnSi2O7 was synthesized by a standard powder solid-state reaction route, and its magnetic properties were studied at low temperature. The magnetic structure was found to be C-type pointing along the c axis from neutron powder diffraction, which is different from the G-type ordering previously reported in all other 2-2-4-2 melilites with manganese as the B'-site transition metal. Ab initio (density functional theory) and magnetic dipole-dipole calculations were used to understand the magnetic structure by determining the spin supersuperexchange parameters as well as the relative influence of spin-orbit coupling and the magnetic dipole-dipole interactions.

Effects of CNTs blending on the superconducting parameters of YBCO superconductor

We report the structural modifications and variation of superconducting parameters of high temperature superconductor (HTSc) YBa2Cu3O7-δ (YBCO) by addition of different wt% of CNTs (0.0, 0.2, 0.4, 0.6, 0.8 & 1.0 wt%) synthesized by standard solid state reaction route. The orthorhombic structure of all the samples with Pmmm space group was confirmed from the X-ray Diffraction (XRD) analysis through Rietveld refinements. No significant variation is observed in the lattice parameters of the orthorhombic structure of YBCO superconducting matrix with increasing wt% of CNTs. The Field emission scanning electron microscope (FESEM) analysis shows better connectivity between the grains of CNTs doped samples. From the temperature dependent resistivity measurement, it is observed that there is no chemical reaction between superconducting YBCO and CNTs, rather addition of CNTs enhances the room temperature resistivity and more importantly reduces the critical temperature (TCon) for lower doped sample and then increases for higher doped sample but not for the pristine one. The paraconductivity studies reveal the 2D-3D transition in parent YBCO and the composites, with a signature of percolative behavior in the composites. Inclusion of CNTs to the YBCO enhances the value of critical current density and gives maximum value of JC which is 12 times more than that of pure YBCO sample for 0.8 wt% of YBCO.