Simple Solid State Reaction Route Research Articles

Optical characteristics, Judd-Ofelt analysis of enhanced luminescence by flux in thermally stable, novel Eu3+- doped BaZr(PO4)2 phosphor for indoor lighting applications

A series of novel single phased Eu3+ doped BaZr(PO4)2 phosphor were synthesized employing simple solid-state reaction route and studied the influence of different chlorides as fluxes (NH4Cl, KCl, LiCl and NaCl) on structural and photoluminescence properties. The structural characterization reveals pure phase formation of the as prepared phosphors with monoclinic crystal structure. The photoluminescence (PL) spectra recorded under 392 nm excitation depicts intense emission at 612 nm. Further, the concentration of Eu3+ ion was well tuned by carefully studying the PL spectra and the optimised amount of Eu3+ ion in BaZr(PO4)2 is found to be 3.0 mol%. The luminescence properties of phosphor with added aforementioned fluxes were also studied in detail. NH4Cl was found to be the best among all the fluxes taken and the photoluminescence intensity of phosphor gets enhanced by 1.43 times of without flux. The Judd-Ofelt theory was employed for determination of spectral parameters from photoluminescent emission spectra. The temperature dependent photoluminescent studies establishes stability of phosphor emission at operating temperatures. The CIE coordinates were evaluated that confirms the pure red emission under n-UV excitation. All the studies indicate the potential of the said phosphor in phosphor converted white light emitting diodes as red emitter and indoor lighting.

NASICON-type Ta5+ substituted LiZr2(PO4)3 with improved ionic conductivity as a prospective solid electrolyte

The need to develop safe solid-state lithium batteries has stimulated intense research efforts for Li+ solid electrolytes. However, the low conductivity limits the development of NASICON LiZr2(PO4)3 (LZP) electrolyte. Here, the doping effects of Ta on the structure, surface morphologies and electrochemical properties of Li1-xZr2-xTax(PO4)3 (LZTP, x = 0, 0.01, 0.02, 0.04, 0.06 and 0.08) solid electrolyte were analyzed. LZTP was prepared using a simple solid-state reaction route, followed by sintering at 1200 °C for 12 h. A proper content of Ta5+ substitution for Zr4+ is beneficial to stabilize the high conductive rhombohedral (α) phase of LZP at room temperature. Doping Ta5+ is conducive to unblocking of Li+ at the M1 site and facilitates the occupation of Li+ at the M2 site, thereby expanding the pathway for Li+ conduction. Rietveld refinement data demonstrated that the Zr–O and P–O bond lengths (dZr-O and dP-O) increased with a decrease in Zr–O–P bond angles (θZr-O-P) as x rose. The distortions in the ZrO6 octahedron may weaken the coulomb attraction in Li+-O2-, resulting in a lower activation energy (Ea) and a higher Li+ conductivity. The highest room-temperature conductivity (6.06 × 10−5 S cm−1) was obtained at x = 0.06, which reached 1.5 × 10−4 S cm−1 at 50 °C. The Ea was found to decrease from 0.388 eV (x = 0) to 0.306 eV (x = 0.06). In addition, Ta doping resulted in improved connectivity and reduced pore formation, which also contributed to the decrease in resistance. The Raman spectrum demonstrated that some phonon modes of bending vibration in PO4 were degenerate and external modes became too weak to be observed or even disappeared as Ta content increased. This change in the modes also had an impact on the Li+ conductivity. Overall, the LZTP-0.06 appears to be a promising candidate for the solid electrolyte.

Influence of co-doping alkali metal ions Li+/Na+/K+ on the luminescence enhancement properties of the blue emission from Pb2+/Bi3+ activated di-barium calcium di-zinc hexa-silicate based phosphors for solid state light applications

The non rare earth element Pb2+/Bi3+ activated and alkali metal Li+/Na+/K+ ions codoped with the silicate based Ba2CaZn2Si6O17 (hereafter mentioned as BCZSO) blue-emitting phosphors were prepared through a simple solid state reaction route and characterized. The phase identification of the as prepared samples was done by taking the powder X-ray diffraction (PXRD). The Rietveld refinement of the as prepared phosphor was analyzed. The morphological analysis was performed using the scanning electron microscope (SEM). The photoluminescence (PL) and PL excitation (PLE) properties of the phosphors were investigated. Exciting the BC1-xZSO:xPb2+ phosphor with 295 nm light yielded a wide blue emission centered at 438 nm. Also, when the BC1-xZSO:xBi3+ phosphor was excited with 317 nm, a bright blue emission at 465 nm was observed. The Stokes shift values of these phosphors were calculated to be 11,067, and 10,040 cm−1 in the same order. The optimum concentrations for the Pb2+, and the Bi3+ ions in the BCZSO host were found to be 3 and 7 mol % respectively. The critical distance (Rc) values were calculated to be 29.32 Å and 23.05 Å for the Pb2+ and the Bi3+ activated BCZSO phosphors respectively. When the alkali metal ions were co-doped in the blue emitting phosphors, a PL enhancement was observed. The decay lifetime was calculated for the BCZSO: M (M:Pb2+/Bi3+) phosphors, and found to decline with increasing concentration of the activators. The CIE color coordinates, and the quantum efficiency of these silicate phosphors were calculated. These values for the BC1-xZSO:xPb2+ phosphor were closer to the commercial blue BaMgAl10O17:Eu2+ (BAM) phosphor. In addition, the temperature dependent photoluminescence (TDPL) spectra were recorded to examine the thermal stability of this phosphor. These results suggest that the BCZSO:M (M:Pb2+/Bi3+) and the BC1-x-yZSO:xPb2+/Bi3+, yLi+/Na+/K+, blue emitting phosphors can serve as promising candidates for white light emitting diodes (WLEDs).

Preparation and photoluminescent property of blue-emitting phosphors Sr5Al2F16:Eu2+

A series of blue-emitting Sr5Al2F16:Eu2+ phosphors were prepared by a simple solid-state reaction route. The phase structure was confirmed by the powder X-ray diffraction (XRD) and the Generalized Structure Analysis System (GSAS) refinement program. Under different monitored wavelengths, due to the multiple and distinguishable sites of Eu2+ ions, the phosphors exhibit different absorption bands. The corresponding mechanisms of luminescence property and concentration quenching behavior were proposed in detail. In addition, the optimum doping concentration of Eu2+ ions was eventually proved to be 2.0 mol%. Finally, the temperature-dependent emission properties of Eu2+ ions in Sr5Al2F16 lattice from 10 K to 510 K were conducted to evaluate the thermal stability. All above results indicate that Sr5Al2F16:Eu2+ phosphors can used as an appropriate candidate for the blue-InGaN chips based white light emitting diode (WLEDs) in future.

Tailoring structural, dielectric and optical effects of PbS nanosheets with Ni doping

We report here the preparation of crystalline PbS nanosheets like structures and their doping with Ni (PbS:Ni). The simple solid-state reaction route is used to prepare pure and doped materials. Initially, x-rays diffraction (XRD) is used to observe the crystallinity and doping effects. Raman spectroscopy is employed to investigate the chemical structure of the prepared pure phase and PbS:Ni materials. The optical response is studied via photoluminescent spectroscopy and we observed that the optical band gap is increased from 1.92 eV to 2.93 eV due to Ni doping. Comparative analysis of all samples with improvement in values of impedance, dielectric constant (20% increase) and electrical conductivities (4% increase) measured by impedance spectroscopy are presented. The dielectric response and improvement show that this material is capable to be used for a variety of applications such as optoelectronic and dielectric devices.

Improvements on sintering behavior and microwave dielectric properties of Li4WO5 ceramics through MgO modification

In this work, compositional modification was proposed to improve the sintering behavior of Li4WO5 via MgO additive. A series of (1-x)Li4WO5-xMgO ceramics were prepared by a simple solid-state reaction route. Solid solutions between Li4WO5 and MgO were formed due to their same crystal structure and the similar ionic sizes. MgO modification improved the microstructure and densification, which in turn increased the dielectric performances of Li4WO5. A composition with x = 0.075 possessed a combination of optimum dielectric properties with a relative permittivity (εr) of 10.8, a quality factor (Q×f) of 26,270 GHz, and a temperature coefficient of resonance frequency (τf) of −8 ppm/°C. The evolutions in dielectric properties with composition were studied from internal effects (ionic polarizability, and packing fraction) and external contributions (density variation). Competing effects from extrinsic and intrinsic contributions give rise to improvements in dielectric properties.

Visible light photocatalytic performance of La-Fe co-doped SrTiO3 perovskite powder

Using simple solid state reaction route, the La and Fe doped SrTiO3 nanoparticle have been successfully synthesized. The effects of different dopant concentrations (1, 2, 3, 4 and 5 wt %) on the characteristics of the as-prepared samples were systematically investigated using various techniques. X-ray diffraction (XRD) investigation exhibit the formation of the cubic perovskite structure of all samples. Field emission scanning electron microscopy (FESEM) images have been confirmed the uniformity and particle size reduction of the samples with increasing of doping elements. Also, the increase of surface area from 9.7 m2/g for pure SrTiO3 to 64.2 m2/g for 5 wt% La-Fe doped SrTiO3 validated by Brunauer-Emmett-Teller (BET) studies. The UV–vis diffuse reflectance spectra (DRS) demonstrate the blue-shift of absorption tail for doped samples as well as reduction of band gap energies (from 3.2 eV to 2.72 eV) with the increase of the doped element. Photoluminescence (PL) analysis of the synthesis nanoparticle display defective states and decline in PL intensity as a result of the doping materials effect in SrTiO3. The 150 min of irradiation time, 0.6 g/L of catalyst dosage, and 5 ppm of initial MO concentration have been obtained as the optimum photocatalyst operating conditions. Also, the photocatalytic investigation reveals the enhancement of degradation rate of Methyl Orange (MO) under visible irradiation for the doped sample. The perfect photocatalytic activity at 4 wt% of Fe-La-doped SrTiO3 nanoparticles is around 19 times higher than that of pure SrTiO3 (96% compare to 5%). In the end, the photocatalytic performance mechanisms are deeply explained.

Synthesis of NiMn2O4 thin films via a simple solid-state reaction route

Herein, NiMn2O4 (MNO) spinel oxide thermistor films were synthesized on a SiO2/Si substrate via annealing the electron beam evaporated Mn–Ni–Mn metal trilayers in air at different temperatures. The X-ray diffraction (XRD) results indicate that polycrystalline spinel-structured MNO thermistor films were formed. The surface particle size of the series MNO films quickly reduced from ~300 to ~120 nm with a temperature increase from 650 to 750 °C, and then, slowly reduced to 80 nm or even smaller with a temperature increase from 750 to 950 °C. Specifically, 750 °C anneal formed the spinel MNO film with largest B value of 5067 and Ea value of 0.4366. The proposed synthesis route for MNO spinel oxide film has been proven to be feasible.

Synergistic effect of hybrid Ce3+/Ce4+ doped Bi2O3 nano-sphere photocatalyst for enhanced photocatalytic degradation of alizarin red S dye and its NUV excited photoluminescence studies

Highly spherical structured Ce3+/Ce4+ doped Bi2O3 nanosphere photocatalyst was prepared by simple solid state reaction route. The crystallite phase of a photocatalyst plays an important role on its activity. Hence, the phase of the catalyst is suitably tuned by varying cerium concentration and calcination temperature. From the experimental data it is evident that, 9 wt% cerium doped Bi2O3 calcinated at 600 °C showed better photocatalytic performance for the degradation of Alizarin red S dye. The enhanced performance of this optimized catalyst is due to synergistic effect by the presence of inter convertible Ce3+/Ce4+ oxidation states and mixed α-β phase Bi2O3. Addition of EDTA-2Na and radical scavengers (Benzoquinone, t-BuOH) decreased the photocatalytic efficiency, which indicates that, the presence of O2, O2− and OH radicals and their significant role in the degradation of ARS dye. A plausible mechanism and degradation pathway of ARS degradation has been proposed.

Modulus Spectroscopy and ac Conductivity of Zn1−xCaxO Ceramics

Ca doped ZnO (Zn1−xCaxO, x = 0,0.01 and 0.02) ceramics were synthesized by simple solid state reaction route. Structural characterization was carried out by X-ray diffraction (XRD) technique. The modulus and ac conductivity of the synthesized ceramics were analyzed by an impedance analyzer. The chemical composition of the synthesized ceramics was confirmed by EDX. The analysis of the XRD peaks revealed the hexagonal wurtzite structure, P63 mc space group for all compositions. The absence of extra peaks in the diffraction patterns indicate that the synthesized ceramics are in single phase. The crystallite size of ZnO decreases with Ca doping and also with increasing concentration of Ca. EDX analysis shows the presence of Ca in ZnO lattice. The frequency dependence imaginary part of modulus suggests the temperature dependent relaxation phenomena in the synthesized ceramics. The sign of long range to short range transition of charge carriers was observed in Ca doped ZnO ceramics. Increase in Ca concentration enhances the capacitance value of the ceramics. The asymmetric peak broadening in modulus predicts a non-Debye type of relaxation mechanism. The modulus studies also confirm the single phase formation of the synthesized ceramics. The ac conductivity increases with increase in frequency and temperature for all samples showing their semiconducting nature. The data of conductivity also shows the NTCR behavior. Again the ac conductivity decreases with Ca doping which may be due to the introduction of defects created by Ca2+ ion in ZnO system.

F-doping and V-defect synergetic effects on Na3V2(PO4)3/C composite: A promising cathode with high ionic conductivity for sodium ion batteries

A facile and simple solid-state reaction route is developed to synthesize F-doping and V-defect Na3V1.98(PO4)3-xF3x/C composites. F-doping is facilitated to decrease the particle size to diminish the pathway of Na+ diffusion. Beneficial by-products are generated due to F-doping and V-defect, Na3PO4 is a typical Na ion conductor and NaVO2 has the layer structure for rapid migration of Na+. The synergetic effect of F-doping and V-defect on the Na+ diffusion is significant. The kinetic behavior is dramatically enhanced and it is beneficial to reinforcing the electrochemical performance. Meanwhile, the extraction of the third Na+ at Na1 site is observed at 4.0 V corresponding to the V4+/V5+ redox couple. The optimized Na3V1.98(PO4)2.9F0.3/C composite delivers an initial charge capacity as high as 143.5 mAh g−1 and an 116.9 mAh g−1 discharge capacity at 0.1C. A reversible capacity of 100.6 mAh g−1 is obtained and it retains 89.3% capacity after 100 cycles at 1C. It presents the highest DNa+ (3.66 × 10−13 cm2s−1), close to three orders of magnitude higher than the Na3V2(PO4)3/C (7.41 × 10−16 cm2s−1). Moreover, Ex situ XRD results demonstrate that broadened channels along x and y directions are favorable to improving DNa+ and it exhibits the highest DNa+ when charging to 3.4 V.

Mn2−x Y x (MoO4)3 Phosphor Excited by UV GaN-Based Light-Emitting Diode for White Emission

One option for low-cost white light-emitting diodes (LEDs) is the combination of a near-ultraviolet (UV) LED chip (382 nm) and a single phosphor. Such Mn2−xYx(MoO4)3 single phosphors have been fabricated by a simple solid-state reaction route and their emission color tuned by controlling the Mn doping amount. The chromaticity coordinates of the white light emitted by the UV GaN LED with the MnY(MoO4)3 phosphor were x = 0.5204 and y = 0.4050 [correlated color temperature (CCT) = 7958 K].

Relaxor Behavior and Dielectric Relaxation in Lead-Free Solid Solutions of (1 − x)(Bi0.5Na0.5TiO3)–x(SrNb2O6)

Lead-free compositions (1 − x) (Bi0.5Na0.5TiO3)–x(SrNb2O6) (BNT-SN) are synthesized by a simple solid state reaction route. SN diffuse in distorted perovskite BNT for low concentrations of SN (x ≤ 0.03) and are stabilized in rhombohedral perovskite phase with experimentally observed relative density of the ceramics >92%. A temperature-dependent dielectric response exhibits a broad dielectric peak that shows frequency-dependent shifts towards higher temperatures reflecting typical relaxor behavior. Modified Curie–Weiss law and Lorentz-type empirical relationships are used to fit the dielectric data that exhibit almost complete diffuse phase transition characteristics. In addition, significant dielectric dispersion is observed in a low-frequency regime in both components of the dielectric response and a small dielectric relaxation peak is observed. Cole–Cole plots indicate the poly-dispersive nature of the dielectric relaxation.

Lithium copper/manganese titanate anode material for rechargeable lithium-ion batteries

In this article, Cu2+ and Mn2+ are chosen as divalent metal cations to dope and synthesize Li2MTi3O8 (M = Cu, Mn, Cu0.5Mn0.5) by a simple solid state reaction route. The structures of Li2MTi3O8 (M = Cu, Mn, Cu0.5Mn0.5) are proved by Rietveld refinement method for the first time. Due to different divalent metal cations M2+ in the structure, Li2MTi3O8 exhibits different electrochemical performances. Li2CuTi3O8 shows the highest initial charge capacity of 242 mAh g−1 and Li2MnTi3O8 displays the lowest initial charge capacity of 139.5 mAh g−1 among all the three samples. Although Li2Cu0.5Mn0.5Ti3O8 reveals a lower initial charge capacity of 174.5 mAh g−1, it exhibits better cycle performance than Li2CuTi3O8 and Li2MnTi3O8. Li2Cu0.5Mn0.5Ti3O8 keeps the reversible capacity of 143 mAh g−1 after 50 cycles at 100 mA g−1 with capacity retention of 82.2%. Besides, the results of electrochemical impedance spectra indicate that lithium ion can move easily in the tunnels of three-dimensional network formed by the (Li0.7Cu0.15Mn0.25)tet, which is in agreement with the result that Li2Cu0.5Mn0.5Ti3O8 performs better electrochemical properties than Li2CuTi3O8 and Li2MnTi3O8. It provides a possibility and theoretical support to synthesize Ti-based materials Li2MTi3O8 with good electrochemical performances.

Enhanced lithium storage capability of sodium lithium titanate via lithium-site doping

In this work, Na2Li2Ti6O14 and its Li-site substitution Na2Li1.9M0.1Ti6O14 (Mn+ = Na+, Mg2+, Cr3+, Ti4+, V5+) samples are synthesized by a simple solid state reaction route and evaluated as anode materials for lithium-ion batteries. Their crystal structures and ion doping behaviors are described and verified by Rietveld refinement. Electrochemical results exhibit that Na+, Mg2+ and Cr3+ dopings can effectively improve the lithium storage capability of Na2Li2Ti6O14. Especially for Na2Li1.9Cr0.1Ti6O14, it shows the best cycling and rate properties among all the as-prepared samples, with a cycling reversible capacity of 262.2 mAh g−1 at 100 mA g−1 and a rate charge capacity of 233.3 mAh g−1 at 700 mA g−1. The enhanced electrochemical properties are contributed to the reduced particle size, decreased charge transfer resistance and improved ionic diffusion coefficient of Na2Li2Ti6O14 via Cr3+ doping. Furthermore, the zero-strain characteristic should also be responsible for the outstanding lithium storage capability of Na2Li1.9Cr0.1Ti6O14. Besides, in-situ X-ray diffraction also reveals that Na2Li1.9Cr0.1Ti6O14 has high structural stability and reversibility during charge–discharge process. Therefore, Na2Li1.9Cr0.1Ti6O14 may be a probable high performance anode material for lithium-ion batteries.

Preparation, electrochemical characterization and in-situ kinetic observation of Na2Li2Ti6O14 as anode material for lithium ion batteries

A novel lithium storage material Na2Li2Ti6O14 is synthesized and reported as anode material for lithium-ion batteries in this paper. The synthesis of Na2Li2Ti6O14 is performed by using a simple solid state reaction route. No impurity can be detected in the final product obtained at a temperature of 900°C. As-formed Na2Li2Ti6O14 is composed of irregular solid particles with the size ranging from 200 to 400nm. Using as anode material, Na2Li2Ti6O14 exhibits flat lithiation/delithiation plateaus with average working potential of 1.28V. Electrochemical testing results show that Na2Li2Ti6O14 can deliver a reversible capacity of 74mAhg−1 with capacity retention of 98.01% upon 50 cycles. Moreover, it also displays excellent rate performance with a charge capacity of 69.5mAhg−1 at 200mAg−1, 64.7mAhg−1 at 300mAg−1, 60.7mAhg−1 at 400mAg−1, and 57.9mAhg−1 at 500mAg−1. The outstanding kinetic behavior is attributed to the high lithium ion diffusion coefficient in Na2Li2Ti6O14, which shows the value ranging from 10−14 to 10−12cm2s−1. Owing to the rapid diffusion kinetics, symmetrical structural change at high rates can be observed by in-situ X-ray diffraction during charge–discharge process.

Lithium storage mechanism in cubic lithium copper titanate anode material upon lithiation/delithiation process

Complex spinel Li2CuTi3O8 with a space group of Fd-3m is prepared for the first time by a simple solid state reaction route. This compound has different space group from the previous reported Li2MTi3O8 (M = Zn, Co, Mg, Ni and Mn) with a space group of P4332. It shows reversibility for lithium storage in the cubic structure. A reversible capacity of 203 mAh g−1 can be delivered at a current density of 100 mA g−1 after 50 cycles with the capacity retention of 70.7%. The electrochemical reaction mechanism between Li2CuTi3O8 and lithium is investigated by various in-situ and ex-situ observations. Rietveld refinement results show that Li2CuTi3O8 has multiple interstitials to accommodate lithium ions during the lithiation process, in which the irregular octahedral 32e sites would be occupied by lithium ions at high working potentials and the regular octahedral 16c sites would be occupied by lithium ions at low working potentials. Besides, a reversible migration of copper ions can found during discharge process. Based on the reverse delithiation process, it is known that the whole charge–discharge process is quasi-reversible for Li2CuTi3O8. Therefore, Li2CuTi3O8 shows high structural stability as a promising lithium storage material for lithium-ion batteries.

Lithium storage behavior of manganese based complex spinel titanate as anode material for Li-ion batteries

Complex spinel Li2MnTi3O8 is prepared by a simple solid state reaction route. Electrochemical test shows that Li2MnTi3O8 reveals excellent electrochemical property as anode material with a reversible capacity of 193.8 mAh g−1 and corresponding capacity retention of 88.0% after 50 cycles. In-situ X-ray diffraction observation reveals that Li2MnTi3O8 shows a quasi-reversible structural evolution during charge–discharge process. For the lithium storage process, lithium-ion initially migrates to 4a position and forms Li–O octahedron at high lithiation potential, and then lithium-ion accommodates 8c position to form Li–O tetrahedron at low lithiation potential. The reverse charge process is quasi-reversible. As a result, Li2MnTi3O8 shows high structural stability as a promising lithium storage material for lithium-ion batteries.

Complex spinel titanate as an advanced anode material for rechargeable lithium-ion batteries

In this work, complex spinel titanates Li2MTi3O8 (M=Zn, Cu, Zn0.5Cu0.5) have been synthesized by a simple solid state reaction route. Their crystal structures are described and verified by Rietveld refinement. Electrochemical results exhibit that Li2CuTi3O8 has a highest lithium storage capacity of 242mAhg−1 and Li2ZnTi3O8 displays the lowest initial charge capacity of 190mAhg−1 among all the three samples. However, both Li2CuTi3O8 and Li2ZnTi3O8 show poor capacity retention and low reversible capacity after 50 cycles. Li2Zn0.5Cu0.5Ti3O8 shows higher structural and cycling stability than that of Li2ZnTi3O8 and Li2CuTi3O8. As a result, Li2Zn0.5Cu0.5Ti3O8 can deliver a reversible capacity of 162mAhg−1 after 50 cycles with capacity retention of 74%.

Effect of Process Parameter Optimization in Reducing Sintering Temperature in the Synthesis and Characterization of Ba(Zn1/3Nb2/3)O3

Controlling the cooling rate during calcination and sintering, phase pure perovskite Ba(Zn1/3Nb2/3)O3 has been prepared by simple solid state reaction route with density >93% at relatively low sintering of 1175°C making it compatible for microwave dielectric applications. The samples are characterized by X-ray diffraction analysis and scanning electron microscopy. The X-ray diffraction shows pure perovskite phase with cubic structure. The lattice constants were obtained a = 4.1032 Å. Detailed studies of ε′ and ε′′ show that the compound exhibits dielectric anomaly at 430°C. Material shows distributed relaxation at higher temperature. Impedance analysis revealed that the impedance is mainly due to the grains. AC conduction activation energies are estimated from Arrhenius plots, and conduction mechanism is discussed.