Solid-state Reaction Procedure Research Articles

Synthesis, structural, impedance, optical, Mössbauer characterizations and magnetic studies of Pb-containing germanate compounds

The orthorhombic antiferromagnetic germanate minerals Pb2Fe2Ge2O9 and Pb2Mn2Ge2O9 have been prepared via solid state reaction procedure. An extensive study of structural, dielectric, optical and magnetic properties of both the germanates have been investigated by employing different measurements such as X-ray diffraction, FTIR, SEM, impedance, UV–Vis–NIR & Mössbauer spectroscopic and magnetometary. Rietveld refinement of room temperature XRD patterns revealed that both the compounds crystallize in the orthorhombic space group Pbcn. FTIR spectrum exhibits the presence of M−O & Ge–O bonds which confirms strong chemical bonding. Morphological analysis through SEM showed good crystallinity of both the samples. The variation of dielectric constant, loss tangent and impedance with frequency have been studied and it has been established that both the germanates are semiconducting at 300K (RT) which may be attributed to the stacking of ions at grain boundaries. The optical band gaps estimated by UV–Vis–NIR spectroscopic measurements further confirms the semiconducting nature of the prepared germanates. 57Fe Mössbauer spectroscopic measurement on synthesized Pb2Fe2Ge2O9 sample was carried out at RT. The obtained values of IS and QS showed that iron is in Fe3+ high spin state (t2g3eg2,s=5/2) and occupy two different sites, Fe1 and Fe2. The field dependent magnetization measurements show that both the compounds display dominant paramagnetic nature at 300K. The temperature dependent magnetization data reveal very sharp first order type AFM to PM transition at TN ∼50K and TN ∼8K for Pb2Fe2Ge2O9 and Pb2Mn2Ge2O9, respectively, and weak FM nature below Neel temperature. The field dependent properties of both the compounds have been analyzed by drawing the M versus H plots at low and room temperatures. The values of calculated effective magnetic moment 6.07μB and 3.95μB for Fe3+ and Mn3+ ions are in the high spin states (t2g3eg2,s=5/2 and )t2g3eg1,s=2.

Extraction and studies of optoelectrical parameters of PVC/Zn0.9M0.1S (M: Co, Fe, Mn, V) films

To be used in optoelectronic applications, the nanocomposites films (doped PVC with Zn0.9M0.1S samples: M = Co, Fe, Mn, V) were prepared in this study. Casting and solid-state reaction procedures were employed to prepare PVC/CMC/Zn0.9M0.1S films. Rietveld refinement method and transmission electron microscope technique were used to investigate the structure and microstructure parameters of Zn0.9M0.1S (M: Co, Fe, Mn, V). X-ray diffraction, Fourier transform infrared and scanning electron microscope techniques were used to study the change in the structure, surface morphology and vibrational bands of PVC polymer upon doping with Zn0.9M0.1S. According to the findings, changing the type of the transition metals in Zn0.9M0.1S caused a change in the host polymer's optical characteristics. Depending on the kind of transition metals in Zn0.9M0.1S, the direct and indirect optical energy gaps of PVC/CMC/Zn0.9M0.1S are irregularly reduced. The direct/indirect optical band gaps of PVC dropped from (5.59, 5.22) eV to minimum values of (5.3, 4.27) eV as it was doped with ZnS. As Zn0.9M0.1S was incorporated into the PVC matrix, the linear and nonlinear optical parameters increased. The fluorescence intensity of pristine PVC is very weak, and it enhanced greatly as it doped with Zn0.9M0.1S. The dielectric constant (ε′), dielectric loss factor (ε″), ac conductivity (σac), the real (M′) and imaginary (M″) parts of the electric modulus changed nonmonotonically with the type of metal in Zn0.9M0.1S. Among all polymers, ′, ″ and σac revealed highest values for the PVC/Zn0.9Co0.1S and the lowest ones for PVC/Zn0.9V0.1S.

The Conductivity Enhancement of 1.5Li2O-P2O5 Solid Electrolytes by Montmorillonite Addition

Most solid electrolyte materials have not shown enough conductivity to be used as an electrolyte for a battery in electronic devices. The mixture of 1.5 Li2O and P2O5 has been reported to show a good conductivity higher than that of Li3PO4, which is thought to be due to phase mixtures that are formed during manufacturing process. Montmorillonite (MMT) was used to explore the effect of phase mixture on conductivity of new 1.5Li2O-P2O5-MMT solid electrolyte composite, which was prepared through conventional solid-state reaction procedures. This study was conducted, how the addition of MMT affects process of forming 1.5Li2O-P2O5-MMT compound, and whether it influences electrical properties and permittivity of compound. Morphology, hygroscopicity, and electrochemical characteristics of this material were analyzed in this study. The shape of glassy-like flakes was reduced in micrographs, and granular lumps were getting larger as MMT was added. Addition also tended to reduce hygroscopicity, as indicated by a reduced rate of porous absorption. Whole Nyquist plot consisted of only one imperfect semicircular arc, indicating only one relaxation process occurred in materials. Capacitance of all arcs indicated main contribution of response was from bulk material. Slope of dielectric loss of samples indicated that conduction in the samples was mainly dominated by dc conduction. MMT clays acted as a medium that absorbed liquid phase in solid-state reaction, increasing formation of dominant phase, which determined total conductivity of compound. Conductivity was higher than that of Li4P2O7, where the sample of 20 wt% MMT addition was most polarizable and most dielectric compound.

LED-light-activated photocatalytic performance of metal-free carbon-modified hexagonal boron nitride towards degradation of methylene blue and phenol.

The present study outlines the transformation of non-photoresponsive hexagonal boron nitride (HBN) into a visible-light-responsive material. The carbon modification was achieved through a solid-state reaction procedure inside a tube furnace under nitrogen atmosphere. In comparison to HBN (bandgap of 5.2 eV), the carbon-modified boron nitride could efficiently absorb LED light irradiation with a light harvesting efficiency of ≈90% and a direct bandgap of 2 eV. The introduction of carbon into the HBN lattice led to a significant change in the electronic environment through the formation of C-B and C-N bonds which resulted in improved visible light activity, lower charge transfer resistance, and improved charge carrier density (2.97 × 1019 cm-3). This subsequently enhanced the photocurrent density (three times) and decreased the photovoltage decay time (two times) in comparison to those of HBN. The electronic band structure (obtained through Mott-Schottky plots) and charge trapping analysis confirmed the dominance of e-, O2 -•, and •OH as dominant reactive oxygen species. The carbon modification could effectively remove 93.83% of methylene blue (MB, 20 ppm solution) and 48.56% of phenol (10 ppm solution) from the aqueous phase in comparison to HBN which shows zero activity in the visible region.

Electronic, optical and magnetic properties of Cu-doped ZnO, a possible system for eco-friendly and energy-efficient spintronic applications.

Polycrystalline Zn1-xCuxO (x = 0.0, 0.02, and 0.05) samples have been prepared using the solid-state reaction procedure. The X-ray diffraction (XRD) patterns of the samples confirm that Cu ions are successfully included in the ZnO hexagonal wurtzite structure. Rietveld analysis of the XRD patterns confirms the phase purity of the synthesized samples and a slight variation in their lattice parameter upon Cu doping. The morphology study by scanning electron microscopy (SEM) depicts transfiguration with Cu doping. The existence of oxygen vacancies (Vo) in the Cu-doped samples is indicated by X-ray photoelectron spectroscopy (XPS). The magnetization measurements reveal the diamagnetic nature of pure ZnO while the Cu-doped samples depict a room-temperature ferromagnetic (RTFM) behavior. The 2% Cu-doped sample shows higher values of both the saturation magnetization and the Vo as compared to the 5% Cu-doped sample. The observed magnetization seems to show a direct relationship with the Vo. The photoluminescence (PL) and ultraviolet (UV) spectroscopic measurements were performed for their optical analysis. The presence of Vo in the Cu-doped samples is revealed by the PL findings also that is in agreement with the XPS results. The UV analysis shows that Cu doping in the ZnO influences the band gap. The observed RTFM induced by Cu doping in ZnO renders it a potential system for spintronic devices useful for energy-efficient data storage devices and energy harvesting eco-friendly applications.

A comprehensive study of structure, oxygen vacancy, and electrical properties of Mg2+ introduced in barium hexaferrite synthesized via spark plasma sintering

Barium hexaferrite BaFe12O19 (BFO) was prepared following conventional solid-state reaction procedure (CSRP) and its’ reformed compound has been prepared following CSRP and spark plasma sintering (SPS) approaches. The Rietveld refinement of synchrotron x-ray diffraction (SXRD) study assured single-phase formation of hexaferrite (M-type with space-group P63/mmc). A dense microstructure appeared in the SPS prepared sample compared to the other compounds. The presence of multiple valances of Fe (Fe2+ along with Fe3+) was studied following modified Mohr’s salt titration (MST) besides of oxygen vacancy estimation. Mg-doped increased oxygen vacancy amount via enhancing Fe2+ in the sample. As a result, the impedance was lower in the Mg-doped BFO (BFMO) samples in contrast to undoped sample, where SPS BFMO further reduced impedance.

Post-synthetic particle size reduction of a layered cesium titanate (Cs2Ti5O11) for the improvement of photocatalytic H2 production

Layered cesium titanate (Cs2Ti5O11) having an elongated rectangular particle shape of size a few hundreds of nanometers has been prepared by size reduction of a macroscopic sample prepared by a previously reported solid-state reaction procedure. The as-prepared material had a particle size of 3 μm (length) and 0.5 μm (width). The described size reduction was accomplished by first pelletizing the Cs2Ti5O11 by pressing it in a mold, and then crushing it in a mortar. The Cs2Ti5O11 samples before and after size reduction were proton-exchanged to obtain H2Ti5O11, which proved to be active for photocatalytic H2 production in the presence of methanol as a sacrificial donor under UV irradiation. In this process, H2Ti5O11 derived from size-reduced Cs2Ti5O11 exhibited higher activity than that derived from the pristine Cs2Ti5O11.

The synthesis and photoluminescence characteristics Bi3+/Dy3+ doped Ca2LaTaO6 phosphors upon the NUV light excitation

The researches on cyan phosphors those can be effectively excited by near-ultraviolet (NUV) light are being hot topics lately because that they have potential applications in phosphor converted white light emitting diodes (pc-WLEDs) based on the NUV chips. In this work, Bi3+/Dy3+ doped Ca2LaTaO6 phosphors were prepared through a solid state reaction procedure, and their luminescence characteristics were investigated through the measurements of the luminescence spectra and the decay curves. The excitation spectra indicate that the Bi3+ or Dy3+ single doped and Bi3+/Dy3+ codoped Ca2LaTaO6 phosphors are suitable for NUV excitation due to the excitation spectra within 250–500 nm. The emission spectra show that the lights of Bi3+/Dy3+ codoped Ca2LaTaO6 phosphors locate in cyan region. The ptotoluminescence characteristics indicate that they have possible uses in pc-WLEDs based on NUV chips.

Near-UV-excited photoluminescence of terbium (Ⅲ)-activated lithium sodium borophosphate phosphor

At present, borophosphate-based fluorescent powder with doped rare earth activators becomes a hot issue in lighting and display industry. Series of Tb3+-activated Li2NaBP2O8 (LNBP) products were constructed via a solid state reaction procedure. The absorption behavior, dopant Tb3+ concentration- and temperature-dependent photoluminescence, and colorimetric properties have been studied in depth. The photoluminescence optimization is as follows: Upon the excitation of near-UV light, the LNBP:Tb3+ product can produce strong visible light with a dominant peak at 544 nm because of the intrinsic 4f optical transitions of Tb3+, and tuning dopant Tb3+ concentration results in the variation of the emitting light color from white to yellowish-green to yellow-green. The LNBP:0.03Tb3+ phosphor possesses the maximal photoluminescence intensity. The finding indicates that the title product with good thermal stability is a promising phosphor for solid state light applications.

New composite Li1.4Mn0.61Ni0.18Co0.18Al0.03O2.4 and LiNi0.5Mn1.5O3.9F0.1 cathode material with higher specific capacity and better capacity retention

Aluminum-modified Li1.4Mn0.61Ni0.18Co0.18Al0.03O2.4 (LNCMA) and fluorine-modified LiNi0.5Mn1.5O3.9F0.1 (LNMOF) cathode materials were successfully synthesized via a solid-state reaction procedure. The discharge capacity of the LNCMA increased from 175.3 to 192.2 mAh g−1, showing approximately a 9.6% improvement after 50 cycles due to Al doping. For the LNMOF cathode, the discharge capacity increased from 116.9 to 174.9 mAh g−1 after F doping, corresponding to an increase of 49.6% after 50 cycles. The new composite cathode was formed by mixing the two cathode materials at a weight ratio of 1:1, which was selected based on the charge–discharge profiles during the first cycle. When the cells were tested in a voltage range of 2.0–4.85 V, the composite material exhibited initial specific capacities of 229.2 and 215.4 mAh g−1, a coulombic efficiency of 94.0% during the first cycle, and a capacity retention of 94.5% after 50 cycles at 0.2C. The concept of inserting irreversible Li ions from the Li-rich material into the 16c vacancy of the LNMOF was validated. The improved capacity was due to the plateau in the discharge capacity curves due to the Mn3+ → Mn2+ reduction. The charge–discharge capacities of the composite material were higher than those in the literature, as was the coulombic efficiency. The new composite material inherited a high-voltage plateau from the LNMOF and a high specific capacity from the LNCMA, and this material has great potential for future applications.

Structural, morphological and magnetoelectric properties of (Bi0.6Ni0.2Ba0.2)(Fe0.6Ti0.4)O3 electronic material

In this work, (Bi0.6Ni0.2Ba0.2)(Fe0.6Ti0.4)O3 magnetoelectric composite has been synthesized using conventional solid state reaction procedure. Form its powder x-ray diffraction investigation the orthorhombic crystal system has been identified. The micrograph shows unique grain growth with different size and shapes. With the help of ferroelectric hysteresis, magnetic hysteresis and magneto electric coefficient has been deliberated. From the ferroelectric hysteresis (P-E loop) the obtained saturation polarization (PS) and remnant polarization (Pr) values are 5.90 µc/cm2 and 1.14 µc/cm2 respectively. From the magnetic hysteresis (M-E Loop) the obtained magnetization saturation (MS) and remnant polarization (Mr) values are 5.45 emu/gm and 1.23 emu/gm respectively. A magnetoelectric coupling coefficient of 55 mv/cm.Oe has been obtained using ME coefficient measurement setup. These studied properties can be useful for developing magnetic and electric field sensor applications.

An attempt to synthesize and study luminescence in CaSiF6

An attempt has been made to synthesis CaSiF6 hexafluorosilicate via simple wet chemical process. So far, very less work has been done in order to study physical and chemical properties of this material. Hence, we have decided to explore its luminescence properties. Though, we are partially successful in preparing this material at room temperature. It is shown that CaSiF6 could be synthesized by the wet-chemical route but the phase purity was poor. It is difficult to prepare these fluoro-silicates by solid state reaction procedures due to their thermal instability. Incorporation of activators in divalent and trivalent form during synthesis itself is further more challenging. Experimental results that we came across have been discussed here.

Influence of gamma irradiation exposure on structural, electrical and magnetic properties of Bi-2223 with Nb2O5 addition

The effects of gamma irradiation on the phase analysis, electrical and magnetic characteristics of Bi-2223 superconductors with Nb2O5 addition were systematically examined. The pristine and Nb-added Bi-2223 superconducting bulk samples were produced by the solid state reaction procedure using high purity oxide powders. The samples were exposed to 1, 5, and 10 kGy gamma ray. The effects of γ-irradiation on the phase analysis, electrical and physical properties of the samples were studied before and after irradiation. The phase formation and the lattice parameters of the samples were characterized by X-ray diffraction (XRD). The superconducting transition temperatures of the samples were determined from the resistance–temperature curve using the four point probe method. The current carrying capacities of all samples were estimated from the magnetization curve using the Bean critical state model.

Low loss and low temperature sintering of Li3Mg2NbO6 ceramics for LTCC applications

We fabricated the low loss Li3Mg2NbO6-xV2O5 (x = 0.25–1.25 wt%)ceramics by the solid-state reaction procedure and discussed the impacts of V2O5 addition on the phase structure, sintering characteristics, microstructure, grain growth, grain size and microwave dielectric characterizations of Li3Mg2NbO6-xV2O5 ceramics. Single-phase Li3Mg2NbO6 orthorhombic structure was obtained for all compositions and substitution of V5+ ions for Nb5+ ions occurred. Homogeneous and dense microstructures with grain size of ∼11.2 μm could be observed when sintered at 925 °C, indicating that suitable V2O5 addition content promoted the grain growth. The relative permittivity was associated with the relative density and the Q × f value was correlated to the grain size and relative density. The τf value was relevant to the porosity corrected relative permittivity. Remarkable microwave dielectric properties: εr = 15.1, Q × f = 91,000 GHz (9.76 GHz) and τf = −24 ppm °C−1 were acquired for the samples with x = 1 wt%, indicating a potential for LTCC applications.

Thermal properties of La0.7Ca0.2Sr0.1MnO3:PdO composites

A systematic study on the thermal conductivity, Seebeck coefficient and specific heat of La0.7Ca0.2Sr0.1MnO3:PdO composites is presented. Solid state reaction procedure was employed to synthesis the samples. It is seen from thermal conductivity (κ(T)) studies that the samples exhibit a slope change nature close to their corresponding magnetic phase transition temperature, TC. The overall magnitude of κ is observed to decrease with increasing Pd concentration. The analysis of Seebeck coefficient data, S(T) versus temperature, T was done using Mott's polaron hopping model reveals that the electron-magnon scattering is governing the low temperature region. The temperature dependent specific heat CP(T) is analyzed to determine the entropy change (ΔS) during the magnetic phase transition.

Conductivity and stability of Li3/8Sr7/16-3x/2LaxZr1/4Ta3/4O3 superionic solid electrolytes

Oxide solid electrolytes Li3/8Sr7/16-3x/2LaxZr1/4Ta3/4O3 (LSLZT, x = 0, 0.025, 0.05) with different A-site vacancy were synthesized using conventional solid-state reaction procedure at 1300 °C. Approximately single-phase perovskite-type was obtained which was analyzed by X-ray diffraction. Moreover, scanning electron microscope, AC impedance spectroscopy and potentiostatic polarization measurement methods were adopted to study the microstructure, Li+ conductivities and electronic conductivities of the samples, respectively. Among these samples, the optimal composition of Li3/8Sr7/16-3x/2LaxZr1/4Ta3/4O3 (x = 0.025) was selected with bulk conductivity of 1.26 × 10−3 S cm−1, total conductivity of 3.30 × 10−4 S cm−1, electronic conductivity of 6.60 × 10−9 S cm−1 at 30 °C and activation energy of 0.28 eV. Furthermore, the cyclic voltammogram analysis indicated the stability of this solid electrolyte at voltages higher than 1.3 V against metallic lithium. The solid electrolyte as a separator in LiFePO4/Li half-cell showed good cycle performance that comprises 98.7% of original values at 0.2 C charge-discharge rates after 50 cycles.

Impedance spectroscopy and conductivity studies of KCl-doped solid electrolyte

(CuCl)4−2x−(KCl)x–CdCl2, x = 0.0–0.4 solid electrolytes were grown via solid-state reaction procedure by suitable heat treatment. An AC impedance spectroscopy suggested that the ionic conductivity mainly arisen from grain effect. A DC electrical conductivity of 3.94 × 10−5 Scm−1 was measured for the x = 0.3 composition at 320 °C. This also shows lowest activation energy in the temperature range of 293–593 K. This has been explained by that fact that at high temperatures thermal disturbances through lattice vibrations take place. In such a high-temperature region, Cu+ readily jumps and migrates at short range, but the number of mutual collisions also increases resulting in a decrease of the Cu+ mobility. The present study reveals that the change in conductivity value depends on concentration of doped ingredient as well as on various parameters in the system. Therefore, these solid electrolytes will be suitable for the development of different electrochemical applications.

Scalable in Situ Synthesis of Li4Ti5O12/Carbon Nanohybrid with Supersmall Li4Ti5O12 Nanoparticles Homogeneously Embedded in Carbon Matrix.

Li4Ti5O12 (LTO) is regarded as a promising lithium-ion battery anode due to its stable cyclic performance and reliable operation safety. The moderate rate performance originated from the poor intrinsic electron and lithium-ion conductivities of the LTO has significantly limited its wide applications. A facile scalable synthesis of hierarchical Li4Ti5O12/C nanohybrids with supersmall LTO nanoparticles (ca. 17 nm in diameter) homogeneously embedded in the continuous submicrometer-sized carbon matrix is developed. Difunctional methacrylate monomers are used as solvent and carbon source to generate TiO2/C nanohybrid, which is in situ converted to LTO/C via a solid-state reaction procedure. The structure, morphology, crystallinity, composition, tap density, and electrochemical performance of the LTO/C nanohybrid are systematically investigated. Comparing to the control sample of the commercial LTO composited with carbon, the reversible specific capacity after 1000 cycles at 175 mA g-1 and rate performance at high current densities (875, 1750, and 3500 mA g-1) of the Li4Ti5O12/C nanohybrid have been significantly improved. The enhanced electrochemical performance is due to the unique structure feature, where the supersmall LTO nanoparticles are homogeneously embedded in the continuous carbon matrix. Good tap density is also achieved with the LTO/C nanohybrid due to its hierarchical micro-/nanohybrid structure, which is even higher than that of the commercial LTO powder.

Dielectric, electrical conduction and magnetic properties of multiferroic Bi0.8Tb0.1Ba0.1Fe0.9Ti0.1O3 perovskite compound

This work focuses on the structural, electrical and magnetic properties of Bi[Formula: see text]Tb[Formula: see text]Ba[Formula: see text]Fe[Formula: see text]Ti[Formula: see text]O3 ceramics, fabricated by solid state reaction procedure. XRD forms of the samples at RT exhibited perovskite phase through the hexagonal structure at room temperature. Dielectric studies of the materials with frequency at different temperatures (25–400[Formula: see text]C) exhibit two dielectric anomalies, first at 175[Formula: see text]C (ferroelectric–ferroelectric transition) and second at around 320[Formula: see text]C (ferroelectric–paraelectric transition). The Curie temperature moved towards the low side temperature with the increase in frequency. The less value of activation energy got for these samples could be attributed to the influence of electronic contribution to the conductivity. A significant change in the magnetic studies was observed for Bi[Formula: see text]Tb[Formula: see text]Ba[Formula: see text]Fe[Formula: see text]Ti[Formula: see text]O3 ceramic. The impedance analysis confirms the non-Debye type nature of the ceramic and relaxation frequency moved to a higher temperature. The Nyquist plot and conductivity studies showed the NTCR behavior of samples. The highest magnetization field was found at temperature [Formula: see text]268.15[Formula: see text]C.

Synthesis, characterization and dielectric properties of xBaTi4O9–(1 − x)BaSm2Ti4O12

Temperature stable microwave dielectric materials xBaTi4O9–(1 − x)BaSm2Ti4O12 were produced through a conventional solid-state reaction procedure in the work. The structural and microwave dielectric properties of the ceramics were determined with the purpose of finding a microwave ceramics with high dielectric constant (er), high quality factor (Q × f) and zero temperature coefficient of resonant frequency (τf). Experimental results showed that BaTi4O9 additions affected grain growth and densification, the grain size distribution, and tuned the dielectric properties of the produced ceramics. The amount of BaTi4O9 strongly influenced the densification and the microstructure (i.e. grain shape and size) of the produced ceramics. Analysis of the experimental results suggests that the microstructural features can be correlated to the dielectric properties of these ceramics. Accordingly, the dielectric constant (er) and the temperature coefficient of resonant frequency (τf) of the produced BaSm2Ti4O12 ceramics can be tuned with the amount of BaTi4O9 additions and the sintering process parameters. The best dielectric properties were achieved for BaSm2Ti4O12 ceramics with 15% BaTi4O9 (er = 66, Q×f = 15,730 GHz and τf ≈ 0 ppm/°C). Experimental results suggest that BaTi4O9 doping improves the dielectric properties of the sintered BaSm2Ti4O12 perovskite ceramics, which are further enhanced by doping with BaTi4O9 in small amounts. However, further increase of BaTi4O9 content jeopardizes them.