Sn Substitution Research Articles

Role of Nb vacancies and Sn substitution in modulating the thermoelectric properties of NbCoSb

Role of Nb vacancies and Sn substitution in modulating the thermoelectric properties of NbCoSb

Energetics of Point Defects in D0a Ag3Sn: First‐Principles Calculations

The Ag3Sn intermetallic compound is commonly found and acts as a strengthening factor in the key lead‐free solders based on Sn‐Ag‐Cu. The Ag3Sn phase exhibits also an asymmetric off‐stoichiometry, which necessitates the existence of constitutional point defects. The presence of point defects can, in general, sensitively affect the plastic deformation of materials and the strengthening role of Ag3Sn in particular. To understand the nature of the point defects and the compositional stability of Ag3Sn, the relaxed structures and the energies of single point defects (vacancies and antisite defects) in all three sublattices of Ag3Sn are calculated at 0 K using ab initio density functional theory (DFT) and the supercell method. The first‐principles‐based calculations predict that the AgSn antisite defect (Ag substitution for Sn) has the smallest enthalpy of formation, thus indicating that the AgSn antisite defect is the dominant point defect in Ag3Sn. The point defect concentrations as a function of Sn content are estimated using the DFT defect energies and the Wagner–Schottky model. The compositional dependence of the point defect concentrations gives new insights on the atomistic mechanisms of formation of nonstoichiometric Ag3Sn.

Unraveling Oxygen Vacancies Effect on Chemical Composition, Electronic Structure and Optical Properties of Eu Doped SnO2.

The influence of Eu doping (0.5, 1 and 2 mol.%) and annealing in an oxygen-deficient atmosphere on the structure and optical properties of SnO2 nanoparticles were investigated in relation to electronic structure. The X-ray diffraction (XRD) patterns revealed single-phase tetragonal rutile structure for both synthesized and annealed Eu-doped SnO2 samples, except for the annealed sample with 2 mol.% Eu. The results of X-ray photoelectron spectroscopy (XPS) emphasized that europium incorporated into the SnO2 host lattice with an oxidation state of 3+, which was accompanied by the formation of oxygen vacancies under cation substitution of tetravalent Sn. Moreover, XPS spectra showed the O/Sn ratio, which has been reduced under annealing for creating additional oxygen vacancies. The pulse cathodoluminescence (PCL) demonstrated the concentration dependence of Eu site symmetry. Combination of XRD, XPS and PCL revealed that Eu doping and following annealing induce strongly disordering of the SnO2 crystal lattice. Our findings provide new insight into the interaction of rare-earth metals (Eu) with host SnO2 matrix and new evidence for the importance of oxygen vacancies for optical and electronic structure formation.

Titanite from the NYF-type pegmatites of Szklarska Poręba Huta quarry, Karkonosze granite massif, SW Poland

Titanite, an accessory mineral of pegmatite related to aplogranite, was identified in the Szklarska Poręba Huta quarry within the Karkonosze granite massif in Lower Silesia, Poland. It formed during pegmatitic to hydrothermal stages. Besides the isovalent substitution Sn → Ti, the chemical composition of the mineral is characterized by three coupled substitutions: (1) (Al, Fe, Sc)3+ + (OH, F)- → YTi + ZO, (2) XREE3+ + Y(Al, Fe, Sc)3+ →X)Ca2+ + YTi4+, and (3) (Al, Fe, Sc)3+ + (Nb, Ta)5+ → 2YTi. These substitutions are strongly dependent on the composition of the magma in terms of its Al2O3/TiO2 activity ratio, with the first one also influenced by the H2O/HF fugacity ratio. Fluorine, which induced the most common substitution (1), had its source in high-temperature F-bearing fluids released from rocks of the metamorphic envelope adjacent to the intruding granite. These fluids mobilized and transported various rock components (Sc, REE, Nb, Ta, etc.) among others in the form of fluoride complexes, enriching the aplogranite magma with some metallic elements. The substitution of Sn for Ti developed with decreasing temperature to the extent that in thin ore-mineralized quartz veins cutting aplogranite, titanite reaches Sn-bearing compositions up to the prevalence of Sn corresponding to malayaite.

Chalcogenide perovskites for solar energy applications: The role of Sn substitution in BaZrS3-based photovoltaic devices

This study investigates the photovoltaic potential of the chalcogenide perovskite BaZr1-xSnxS3, where x values of 0, 0.125, and 0.250 were chosen. The band gap of BaZrS3 (1.7 eV) is slightly larger than the optimal band gap for single-junction devices, and alloying with Sn has been explored to tune the band gap. The photovoltaic performance of devices with different absorber layers was simulated using the SCAPS-1D solar cell simulator software. The results show that the power conversion efficiency (PCE) increases with increasing Sn content, and the optimal PCE is achieved at x = 0.125. The effects of temperature, work function of the back contact, and band offset at the ETL/absorber and absorber/HTL interfaces on the device performance were also investigated. The results show that the PCE decreases with increasing temperature, and the optimal PCE is achieved at a back contact work function of 4.8 eV. The study shows that tailoring band offset at the ETL/absorber and absorber/HTL interfaces can lead to efficiencies about 20 %, highlighting BaZr1-xSnxS3 as a promising material for future high-efficiency solar photovoltaics.

Unravelling Structural, Optical, and Band Alignment Properties of Mixed Pb-Sn Metal-Halide Quasi-2D Ruddlesden-Popper Perovskites.

Lead-tin (Pb-Sn) mixed-halide perovskites show potential for single-junction and tandem solar cells due to their adjustable band gaps, flexible composition, and superior environmental stability compared to three-dimensional (3D) perovskites. However, they have lower power conversion efficiencies. Understanding band alignment and charge carrier dynamics is essential for enhancing photovoltaic performance. In this view, herein we have prepared thin films of mixed Pb-Sn-based two dimensional (2D) Ruddlesden-Popper (RP) perovskites BA2FA(Pb1-xSnx)2I7 using a solution-based method. XRD study revealed the formation of orthorhombic phases for pristine (BA2FAPb2I7) and mixed Pb-Sn perovskite thin films. UV-vis analysis showed that different n = 2 and n = 3 phases are present in the pristine sample. In contrast, Pb-Sn-doped samples showed no signature of other phases with a prominent red-shift in the visible spectral region. Cyclic voltammetry showed peaks for electron transfers at the band edges. Additionally, electrochemical and optical band gap matching was observed, along with decreased peak intensity due to less reactant and altered electrolyte-perovskite interface stability. Density functional theory (DFT) calculations revealed that the reduced band gap is due to the alteration of electrostatic interactions and charge distribution within the lattice upon Sn substitution. Low-temperature PL analysis provided insights into charge carrier dynamics with Sn substitution and suggested the suppression of higher n phases and self-trapped excitons/carriers in mixed Pb-Sn quasi-2D RP perovskite thin films. This study sheds light on the electron transfer phenomena between TiO2 and SnO2 layers by estimating band offsets from valence band maximum (VBM) and conduction band minimum (CBM), which is crucial for future applications in fabricating stable and efficient 2D-Pb-Sn mixed perovskites for optoelectronic applications.

Copper Functionalized SnSe Nanoflakes Enabling Nonlinear Optical Features for Ultrafast Photonics.

This study enhances the ultrafast photonics application of tin selenide (SnSe) nanoflakes via copper (Cu) functionalization to overcome challenges such as low conductivity and weak near-infrared (NIR) absorption. Cu functionalization enhances concentration, induces strain, and reduces the bandgap through Sn substitution and Sn vacancy filling with Cu ions. Demonstrated by density functional theory calculations and experimental analyses, Cu-functionalized SnSe exhibits improved NIR optical absorption and superior third-order nonlinear optical properties. Z-scan measurements and femtosecond transient absorption spectroscopy reveal better performance of Cu-functionalized SnSe in terms of nonlinear optical properties and shorter carrier relaxation times compared to pristine SnSe. Furthermore, saturable absorbers based on both SnSe types, when integrated into an erbium-doped fiber laser, show that Cu functionalization leads to a decrease in pulse duration to 798 fs and an increase in 3dB spectral bandwidth to 3.44nm. Additionally, it enables stable harmonic mode-locking of bound-state solitons. This work suggests a new direction for improving wide bandgap 2D materials by highlighting the enhanced nonlinear optical propertiesand potential of Cu-functionalized SnSe in ultrafast photonics.

Study on the possibility of band gap widening of thermoelectric semiconductor α-SrSi2 by isoelectronic elements incorporation

The material α-SrSi2 has considerable application potential as a near room temperature thermoelectric material. However, it has a very narrow band gap which can vanish due to impurities, defects, and grain boundaries. To obtain guidelines for controlling the band gap and improving the thermoelectric properties, we have studied the substitution of isoelectronic impurities (Mg, Ca, and Ba for Sr, and C, Ge, and Sn for Si) through first-principles calculations using the Gaussian-Perdew-Burke-Ernzerhof hybrid functional. From these calculations, it was found that:(1) The band gap change due to Ca, Ba, Ge, and Sn substitutions is almost the same as that predicted from the change in the lattice constant of pure α-SrSi2.(2) Substitution with C was energetically unfavorable and therefore high levels of substitution would be difficult to achieve. However, it was expected to increase the band gap, contrary to the prediction from the decrease in the lattice constant.(3) An increase in the Mg substitution of the Sr site from 0 at. % to 8 at. % caused a decrease in the lattice constant from 0 % to −1.189 %

Influence of Sn addition on the phase formation, microstructure and magnetic properties of Mn-Bi alloy ribbons

In this work, the phase formation, microstructure and magnetic properties of Mn54Bi46−xSnx (x = 0, 1, 2, 3 and 4) alloy ribbons fabricated by melt-spinning method combined with annealing were investigated. The fraction of the low-temperature MnBi phase (LTP-MnBi) depends not only on the Sn concentration but also on the annealing regime. In the as-quenched ribbons, the fraction of the LTP-MnBi decreases monotonically from 38.1 to 21.1 wt% when the Sn concentration increases from 0 to 4 at%. Meanwhile, the fraction of this phase increases significantly from 69.0 to 83.2 wt% when the Sn concentration changes from 0 to 2 at% and tends to decrease upon further increasing the Sn concentration to 4 at% for the ribbons annealed at 250 °C for 16 h. Saturation magnetization, Ms, of the annealed samples changes consistently with the fraction of LPT-MnBi and reaches a maximum value of 70.4 emu/g in the sample with Sn concentration of 2 at%. The addition of Sn also aids in refining the grains, leading to an improvement in the hard magnetic properties of the material. The coercivity, Hc, of the alloy ribbons tends to increase as the Sn concentration increases and changes non-monotonically with annealing time. The maximum energy product, (BH)max, reached 5.5 MGOe in the sample with x = 2, demonstrating the promise of Mn-Bi based alloys in practical applications. The density functional theory calculations were also performed to clarify the effect of Sn addition. The calculated results confirmed the decrease in the lattice parameters with Sn substitution in the experimental data. The total magnetic moment per formula unit and the evaluated saturation magnetization are 3.62 µB and 78.28 emu/g, respectively, for Sn substitution of ∼3.1 at%. (Although the total magnetic moment decrease with doping, the saturation magnetization per unit mass could be improved.)

Defect induced Raman shifts and bandgap engineering in layered SnSe2+δ bulks

In the context of the extensive application prospect of two-dimensional (2D) chalcogenides, we synthesized layered SnSe2+δ bulks with defects employing a hybrid chemical vapor transport-melt approach. Both the Eg and A1g Raman characteristic peaks in SnSe2+δ are dominated by cubic anharmonicity, coupled with nonlinear temperature dependencies below 140 K. Notably, the reduction in phonon energy observed in these vibrational modes can be ascribed to defect-mediated Raman scattering, irrespective of deficient or excess Se defects. However, the lower consistency in the Raman shifts of the in-plane Eg vibrations compared to the out-of-plane A1g modes suggests that the defects predominantly entail the absence of Se atoms and the substitutions of Sn by Se, delineating a continuum of Se-deficient and Se-enriched compositions. Furthermore, Se defects induce the contraction of the indirect bandgaps, facilitating a transition from medium to narrow bandgap semiconductors in SnSe2+δ, which underscores the tunable nature of the bandgaps through the incorporation of Se defects. These discoveries present an avenue for bandgap engineering and foster a deeper comprehension of the phonon and thermal properties of layered chalcogenides for further advanced technologies.

Comprehensive analysis of Ni0.4Cu0.2Zn0.4Fe2-4xSn3xO4 nanospinel ferrites: Structural, electrical, and dielectric characterization through advanced techniques

This study extensively investigates Ni0.4Cu0.2Zn0.4Fe2-4xSn3xO4(x ≤ 0.10) nanospinel ferrites, denoted as NCZFe2-4xSn3xO4 NSFs, focusing on their structural, morphological, electrical, and dielectric characteristics. Utilizing various techniques such as SEM, EDX, TEM, XRD, and impedance analysis, the research confirms the cubic spinel structure and composition of the nanoferrites. The substitution of Sn4+ ions into Ni0.4Cu0.2Zn0.4Fe2O4 NSFs is explored, with a thorough examination of dielectric and electrical parameters up to 1.0 MHz and temperatures ranging from 20 to 180 °C. Complex impedance spectroscopy is employed to represent these parameters in a logarithmic 3D graph, revealing insights into ac/dc conductivity, activation energies, dissipation factor, dielectric constant, and loss. The study observes adherence to the power-law frequency rule in ac conductivity and highlights the impact of temperature and substitution ratios on grains, grain boundaries, and elemental composition. The investigation suggests a conduction mechanism involving electron and polaron hopping, and ionic contributions. Dielectric parameters show frequency-dependent changes that relate the dielectric constant to space charge polarization, inhomogeneous dielectric structure, impurities, and grains/grain boundaries. Cole-Cole impedance plots display semicircles dependent on substitution ratios and temperature, emphasizing contributions from grains, grain boundaries, and ionic mobilities. The Nyquist plots of Cole-Cole impedance functions further underscore substantial complexity in the conduction mechanism of the substituted NCZFe2-4xSn3xO4NSFs.

Substitution of Sn in the high-permeability MnZn ferrite for wide temperature applications

To meet the challenge of varied working temperatures of inductance components in new energy vehicle and 5G communication, the high-TC high-permeability MnZn ferrite with excellent temperature stability was developed by the addition of SnO2. In this series of samples, initial permeability μi maintains large values in a wide temperature range. With increasing the SnO2 content, the temperature of the second permeability peak Tsp decreases and meanwhile Curie temperature TC maintains as high as 160 °C. For the best sample with 6000 ppm SnO2, μi at 25 °C is 7244 and exhibits the excellent temperature stability with the low specific temperature coefficient of 0.35 × 10−6 °C−1 between 25 and 130 °C. The addition of SnO2 generates Fe2+ and adjusts the magneto-crystalline anisotropy constant K1 = 0 point, which is responsible for the wide-temperature high permeability. The effect of SnO2 addition on magnetization process has also been clarified.

Tuning structural, dielectric, and ferroelectric properties of BTO-based ceramics through dual-site substitution

Different strategies for tuning the properties of ferroelectric materials have been employed for advancing electromechanical applications. Among several material synthesis techniques explored, site substitution is an effective approach. The present work focuses on Ba1-xCaxSnyTi1-yO3 (BCST) ceramics prepared by solid-state sintering route with different substitution levels (x = 0, 0.05 and y = 0, 0.09). The impact of site substitution on the properties of Barium Titanate (BTO), phase purity, structural analysis, chemical composition, dielectric, and ferroelectric properties have been studied. An ionic radii difference at A-site and B-site substitution is a key factor to achieve significant changes in physical and structural properties. X-ray diffraction patterns ensure the formation of pure phase perovskite structure in all the compositions. Raman spectroscopy indicates Ca substitution not only occurs at the A-site but also within the oxygen octahedra, adversely affecting the properties. Ca and Sn act as strong grain growth inhibitors, leading to a fine-grained and dense microstructure in BCST. While Ca substitution has a limited impact on the Curie temperature (TC), Sn substitution lowers TC in BST (54 °C) and BCST (50 °C) compared to BTO (126 °C). The Sn substitution results in the coexistence of multiple phases (rhombohedral, tetragonal and orthorhombic) in BST, enhancing its properties (ε' = 6118 at RT, Pr = 5.50 μC/cm2, Q11 = 0.060 m4/C2, d*33 = 526 pm/V) in comparison to BTO. These results acknowledge the role of substituents in lattice disruption, paving the way for chemistry-based materials design in the field of dielectric, actuator and energy storage applications.

Systematic trends in the substitution mechanisms of minor elements in cassiterite

A dataset of 4751 EPMA point analyses on cassiterite crystals from 18 localities spanning a range of different granite-related Sn-bearing mineral systems was investigated and compared with thermodynamic considerations from speciation and lattice strain models. The existence of previously inferred charge balanced coupled substitution mechanisms of Fe3+, Fe2+, Mn2+, Nb5+, Ta5+ and W6+ for Sn4+ are confirmed. The homo­valent substitution of Sn4+ by Ti4+ and Zr4+ is also confirmed, and the first evidence for homovalent substitution of Nb4+ and W4+ in natural cassiterite is presented. The preferred substitution mechanisms for Ti, Fe, Mn, Nb, Ta, W and Zr vary systematically as a function of the mineralising environment. Cassiterite precipitated from silicate liquid dominated systems (such as in pegmatites) primarily display a coupled Fe–(Nb,Ta) substitution mechanism with a 1:2 stoichiometry, whereas cassiterite precipitated in systems dominated by autometasomatic processes (such as greisens) more closely follow a 1:1 stoichiometry, as well as increased levels of Ti. Cassiterite precipitated solely from hydrothermal fluids (such as Sn–(W) quartz vein systems) exhibit the highest Ti concentrations, with lower contents of Fe–(Nb,Ta) coupled substitutions, instead displaying a switch to the incorporation of Fe3+ via FeO.OH stoichiometry. Hydrothermally precipitated cassiterite from skarn systems display the highest Fe3+ contents, and the lowest Nb, Ta and Ti contents. These systematic changes define a continuous trend in a Ti–(Fe + Mn)–(Nb,Ta) ternary diagram, allowing for classification of the primary source of alluvial cassiterite.

Insight into Na and Sn substitutions on structural, electronic and thermodynamic responses of Li2FeSiO4 for next generation Li+-ion based batteries: A first principles study

In this study, Li2FeSiO4 has emerged as a promising alternative cathode material for next-generation Li-ion-based batteries due to its high theoretical capacity. We used spin density functional to investigate the structural, electronic, and thermodynamic responses of the pure and doped Li16Fe8Si8O32 system. In the Li-site is substituted by Li61Na3Fe32Si32O128, Li59Na5Fe32Si32O128, Li56Na8Fe32Si32O128, and in the Si-site, Li64Fe32Si31Sn1O128, Li64 Fe32Si30Sn2O128, Li64Sn4Fe32Si28O128 atoms, employing the Perdew-Burke-Ernzerhof (PBE) with generalized gradient approximation (GGA). The introduction of dopants induces significant modifications in the lattice parameters and corresponding volumes, thereby affecting the overall structural characteristics. The computed band gaps of both systems experience a decrease in the presence of dopants, indicating an enhancement in electronic conductive responses. The calculated results show that the band gap of Na-doped can be changed from 2.66 eV to 1.94 eV, and Sn-doped can be changed from 2.66 eV to 0.89 eV, respectively. The element, partial, and total density of states investigations reveal impurity states created by the modified atoms extending to the conduction band maximum. Intriguingly, Na and Sn concentrations in the pure system contribute to modified electronic conductivity attributed to volumetric expansion, a narrowed band gap, and reduced ionic bonding. In this analysis, we have recognized four new thermodynamically stable systems within the Li–Si–Fe–O system, both pure and dopant systems complementing each other. The computational investigations presented here are expected to contribute to a deeper understanding of the doping effects on Li2FeSiO4, facilitating further advancements in cathode material design for Li-ion batteries.

Synthesis and Exploration of Barium Stannate-Zirconate BaSn1-xZrxO3 (0 ≤ X ≤ 1) Solid Solutions as Photocatalysts.

Employing ionic liquid-assisted microwave synthesis and moderate heat treatment allows for the preparation of otherwise difficult-to-obtain perovskite-type BaSn1-xZrxO3 solid solutions (0 ≤ x ≤ 1). The impact of substituting Sn for the crystal structure, crystallinity, morphology, and photocatalytic performance was investigated. The obtained materials are characterized by X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller (BET) surface area analysis, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, and Raman and IR spectroscopy. SEM images show that the morphology of the samples varies from rods for x = 0, 0.2 to spherical for x = 0.5, 0.8, 1. Upon Zr for Sn substitution, the band gap changes from 3.1 to 5.0 eV as the valence and conduction bands move to lower and higher energies. The photocatalytic activities of the BaSn1-xZrxO3 samples in the hydroxylation of terephthalic acid (TA) follow the order BaSn0.5Zr0.5O3> BaSn0.8Zr0.2O3> BaSnO3> BaSn0.2Zr0.8O3> BaZrO3. The superior photocatalytic activity of BaSn0.5Zr0.5O3 can be attributed to the synergistically favorable combination of a suitable band structure, band gap size, and increased surface area-to-volume ratio, resulting in a diminished crystalline particle size unattainable from samples prepared via traditional synthetic routes or without ionic liquid.

Microwave-synthesized aluminum, gallium and indium-substituted stannite nanocrystal absorbers for solar cell applications

A novel family of Cu2FeXS4-x (X = Sn, Al, Ga & In) semiconductors with tetragonal stannite crystal structurehave been designed by a simple microwave assisted method. The impact of microwave power on the morphological, structural,spectroscopic and electrochemical properties were investigated. X-ray Diffraction (XRD) clearly revealed that the complete substitution of Sn (0.69 Å) with Al (0.54 Å), Ga (0.62 Å) and In (0.80 Å) did not affect the tetragonal arrangement of the stannite crystal structure except for a slight peak shift. High resonance scanning and transmission electron microscopy (HRSEM and HRTEM) revealed nano bullets, hexagonal prism, triangular nanoplates and spherical morphology with nanocrystal sizes ranging from 8 to 13 nm for CFXS nanocrystals. The UV–visible spectroscopy shows strong light absorption in the whole visible range with band gaps of between 1.2 and 1.6 eV suggesting its potential application as an absorber in thin film solar cells. Doctor blading method was used to coat CFXS nanocrystal inks on CdS coated ZnO nanorod arrays to fabricate a superstrate solar cell devices with the architecture ITO/ZnONRs/CdS/CFXS/Ag. The solar cell devices fabricated with copper iron tin sulfide (CFTS), copper iron aluminium sulfide (CFAS), copper iron gallium sulfide (CFGS) and copper iron indium sulfide (CFIS) absorbers displayed a power conversion efficiency (PCE) of 0.21%, 0.15%, 0.58% and 0.41% respectively. The photovoltaic response exhibited by the novel materials is quite positive and this shows that they can in fact be utilized to design solar cells with strong photovoltaic properties.

Enhanced Thermoelectric Properties of P-Type Sn-Substituted Higher Manganese Silicides.

This study introduces Sn-substituted higher manganese silicides (MnSi1.75, HMS) synthesized via an arc-melting process followed by spark plasma sintering (SPS). The influences of Sn concentrations on the thermoelectric performance of Mn(Si1-xSnx)1.75 (x = 0, 0.001, 0.005, 0.01, 0.015) are systematically investigated. Our findings reveal that metallic Sn precipitates within the Mn(Si1-xSnx)1.75 matrix at x ≥ 0.005, with a determined solubility limit of approximately x = 0.001. In addition, substituting Si with Sn effectively reduces the lattice thermal conductivity of HMS by introducing point defect scattering. In contrast to the undoped HMS, the lattice thermal conductivity decreases to a minimum value of 2.0 W/mK at 750 K for the Mn(Si0.999Sn0.001)1.75 sample, marking a substantial 47.4% reduction. Consequently, a figure of merit (ZT) value of ~0.31 is attained at 750 K. This considerable enhancement in ZT is primarily attributed to the suppressed lattice thermal conductivity resulting from Sn substitution.

The role of Sn and Zn substitutions on the magnetic properties of nanosized Y-type hexaferrite prepared by sol-gel auto-combustion method

The current paper has focused on the improvement of the magnetic performance of the Sn, Zn-doped Y-type hexaferrite nanoparticles via the sol–gel auto-combustion method. The partial replacement of nonmagnetic Zn2+ and Sn4+ cations for the magnetic Fe3+ cation was studied. At the low Zn-Sn concentration, the Sn4+ cations had a preference for octahedral locations (12k, 2a, 4f2) and the Zn2+ cations had a strong tendency to move to the tetrahedral spaces (4f1), respectively. Based on this data, the single-phase hexaferrites with the chemical formula of Sr2Co1.7Mg0.3Fe(12-x)Snx/2Znx/2O22 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) were successfully synthesized via the sol–gel auto-combustion method. The x-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), Thermal Gravimetric Analysis (TGA), Differential Thermal Analysis (DTA), Field Emission Scanning Electron Microscopy (FESEM) and Vibrating Sample Magnetometer (VSM) were carried out to investigate the obtained ferrite performance. The results revealed the formation of the single-phase platelet-like Y-type hexagonal ferrites after calcinations at 1000 °C with a thickness of 30–70 nm and a particle size of 90–210 nm. The obtained nanosized ferrites had the magnetic coercivity (Hc) and the saturation magnetization (Ms) in the range of 2100–637 Oe and 38–48 emu g−1, respectively. The addition of Sn, Zn dopants enhanced the saturation magnetization and reduced the magnetic coercivity, which can make this ferrite a candidate for some applications.

Enhanced performance of Sn-doped Na3V2(PO4)3 with CNT integration for high-efficiency sodium-ion batteries

The development of Na3V2(PO4)3 (NVP) has been severely hindered by low conductivity and unstable crystal structure. A simultaneously optimized strategy of Na-rich and Sn substitution is proposed for the first time. SnX-NVP@CNTs with different doping gradients are successfully prepared by the facile sol-gel method. Notably, more hole carriers can be generated by introducing Sn2+, thus improving its electron transport efficiency. In addition, since Sn2+ ions have a larger ion radius; when replacing V3+ ions at pillar positions, the lattice spacing can be enlarged to improve the structural stability of electrode materials. Meanwhile, it is beneficial to the movement of deep-level Na+ ions and improves the utilization rate of electrode materials. Moreover, to achieve charge compensation, it is necessary to introduce excess Na+ to the Sn-doped NVP system, which will increase the number of Na+ involved in the deintercalation process and improve its reversible capacity. Furthermore, the dense coating of CNTs can form an efficient conductive network structure, which improves the electron transport rate and inhibits the accumulation of active grains to accelerate Na+ diffusion. Under the synergistic adjustment of Sn2+ doping and CNTs enwrapping, the prepared Sn0.07-NVP@CNTs exhibit a high reversible capacity of 115.1 mAh/g at 0.1C, and the capacity retention rate reaches 89.35 % after 2000 cycles at 10C. Even after 10,000 cycles at 60C, its reversible capacity dropped from the initial 75.9 to 51.3 mAh/g, with a capacity loss of only 0.003 % per cycle. Besides, the Sn0.07-NVP@CNTs//CHC full battery releases a capacity of 139.9 mAh/g, highlighting its great potential for actual applications.