Increase In Lattice Parameter Research Articles

Enhancing thermoelectric properties of p-type CoSb3 skutterudite by Fe doping

In this report, we have successfully synthesized thin films of Co1-xFexSb3 (0 ≤ x ≤ 0.1) using electrochemical deposition technique. The electrical and thermoelectric properties of CoSb3 thin films have been investigated by varying the concentration of Fe. X-ray diffraction analysis confirms formation of single phase of Co1-xFexSb3 (0 ≤ x ≤ 0.05) with increase in lattice parameter indicating incorporation of Fe at the Co site. The X-ray photoelectron spectroscopy study reveals that Fe2+ substitutes Co3+ thus generating excess hole carriers, further confirmed by the positive signs of Seebeck and Hall coefficients. It is noted that the thermoelectric properties are mainly controlled by Fe substitution in terms of increasing carrier effective mass as well as phonon scattering. Fe substitution does not significantly alter the carrier mobility and thus confining the transport properties to be mainly leveraged by carrier concentration. Scanning thermal microscopy is used to study the effect of Fe incorporation on the thermal conductivity of nanostructured Co1-xFexSb3 thin films. Enhanced value of power factor and relatively lower value of average thermal conductivity for Co1-xFexSb3 sample is achieved at an optimized value of 5% Fe, as a result of enhanced electron transport and phonon scattering. Furthermore, the improved thermoelectric performance makes this natural-abundant, non-toxic and cheap CoSb3:Fe material a very promising candidate for low cost thermoelectric energy generation.

Impact of Zn2+-Zr4+ substitution on M-type Barium Strontium Hexaferrite’s structural, surface morphology, dielectric and magnetic properties

We report the synthesis of Ba0.5Sr0.5ZnxZrxFe12-2xO19 (x = 0.00–1.00) samples using sol–gel auto combustion method. The Rietveld refinement of XRD data indicates a) pure phase formation, b) increase in lattice parameters with composition and c) the absence of undesirable phases such as α–Fe2O3, BaCO3 and SrCO3. FESEM and TEM micrographs reveal an increase in grain size with ‘x’. The broadening of Raman peaks without any peak shift in all the samples indicates that the Zn2+/Zr4+ions are incorporated into Ba0.5Sr0.5Fe12O19 without altering the local structure. Magnetic measurements reveal that the maximum value of saturation magnetization (Ms) is 67.37 emu/g in x = 0.4 sample. The coercivity (Hc) monotonically decreases from 4.936 KOe to 1.029 KOe with increasing concentration of non-magnetic dopants. The dielectric constant values decreases monotonically as function of frequency for all the samples. The samples because of their superior magnetic properties could be vital for high density perpendicular recording, high density parallel recording EM shielding and permanent magnet applications.

Crystalline growth and alloying of In[formula omitted]Ga[formula omitted]Sb films by electrodeposition onto liquid metal electrodes

Incorporating indium (In) atoms into the GaSb lattice provides broad tunability of the optical bandgap within the infrared spectral region. This research documents the first instance in the literature of electrochemical liquid–liquid–solid (ec-LLS) growth of a ternary semiconductor alloy. Indium content of deposited InxGa1−xSb samples was regulated by controlling the Ga/In ratio of the liquid metal electrode. All depositions were performed using a single-step growth method under ambient pressure at 90 ± 5 °C. X-ray diffraction analysis showed shifts of the (111) diffraction peaks toward the peak locations of cubic InSb for the x=0.50, 0.60, and 0.70 samples, indicating a consistent increase in lattice parameter. However, the x=0.28 and 0.41 samples displayed unexpected shifts toward larger angles, possibly due to increased presence of Ga vacancies and antisites caused by Ga-rich growth conditions, as well as insufficient mixing of the liquid metal electrode for x< 0.50. Optical bandgaps ranging from 0.594 to 0.707 eV were determined via the Tauc method and Kubelka–Munk theory applied to diffuse reflectance data, and showed general agreement with measured lattice constants. Data obtained in this research supports In incorporation into the GaSb lattice for samples with x≥ 0.50, but with significantly lower In compositions relative to the liquid metal electrode. No general trend was observed for average crystallite size as a function of In composition, likely due to inconsistencies in the film harvesting process. This research provides further support for ec-LLS as a semiconductor growth technique capable of crystalline growth and alloying of III-V semiconductors.

Improved electrochemical activity of the Li2MnO3-like superstructure in high-nickel Li-rich layered oxide Li1.2Ni0.4Mn0.4O2 and its enhanced performances via tungsten doping

Voltage decay of Li- and Mn-rich layered oxides can be effectively suppressed by increasing their Ni contents, which however normally results in a sizable decrease in capacity probably due to the reduced Li2MnO3-like superlattice component. Here, we reveal that the partial replacement of Mn by W in the high-nickel Li-rich (HNLR) layered oxide Li1.2Ni0.4Mn0.4O2 leads to the increase in both Li2MnO3-like superlattice component and Ni2+ proportion due to the presence of W6+. As a result, the doping of W favors the activation of the Li2MnO3-like component with the reversible redox of more oxygen anions and the creation of a multi-cation chemical environment, accompanied by the size reduction of primary particles and the increase in lattice parameters. The reversible redox of more oxygen anions results in much higher capacity and initial Coulombic efficiency. The reduced sizes of primary particles, along with the lattice expansion significantly enhance the electrochemical kinetics, which accounts for superior rate capability and excellent high-rate cycling performance. This study opens a possibility of improving the performance of HNLR oxides by doping appropriate elements to modify and optimize the properties of the Li2MnO3-like component.

Effect of Solute Carbon on the Characteristic Hardening of Steel at High Temperature

Small ball rebound hardness tests demonstrated characteristic hardening at 700 K in the ultra-low carbon and pearlitic steels. The equilibrium phase diagram of Fe-C binary alloy calculated using Thermo-Calc exhibited dissolving of cementite above 700 K. Moreover, in-situ heating neutron diffraction measurement demonstrated the increase of lattice parameter by dissolving of cementite above 700 K. Therefore, it can be concluded that the characteristic hardening above 700 K can be attributed to the solid solute carbon.

Effect of Co substitution on structural and magnetic properties of Ni0.6Zn0.4Fe2O4 nanoferrite

Nano particles of Ni0.6-xCoxZn0.4Fe2O4 (x = 0.1, 0.2, 0.3, 0.4, 0.5) were synthesized by sol–gel auto-combustion method. The synthesized samples were characterised to study their stoichiometric, structural and magnetic properties. X-ray powder diffraction patterns confirmed single phase cubic spinel structure. The increase in lattice parameter with increase in cobalt content was observed. The crystallite sizes calculated using Debye–Scherrer formula were found to be in the range from 14 nm to 19 nm. Vibrational properties of nanoparticles were studied using FTIR spectra recorded in the transmittance mode. The energy dispersive X-ray spectroscopy confirmed the chemical composition of the samples. The SEM images of the samples showed spherical shaped nano particles. The decrease in Curie temperature with increase in Co content was found using AC susceptibility measurements. The saturation magnetization values of as prepared samples obtained from vibrating sample magnetometer (VSM) at room temperature were found to be in the range between 44.25 and 55.8 emu/g. The low coercivity value confirmed the soft nature of prepared ferrites.

Investigation of Structural, Electronic and Magnetic Properties of HoMg: An ab-initio Study

The structural, electronic and magnetic properties of HoMg are investigated. Different exchange-correlation functional were used for structural optimization, but LDA scheme shows the excellent result. The calculated values of lattice constants in B1 and B2 phases are 6.21(Å) and 3.74 (Å), respectively. The present calculation shows that the ground state configuration of HoMg lies in B2 phase. The calculated band structure shows that HoMg has metallic nature. In magnetic properties, the magnetic moment of HoMg in B2 phase is also presented. Magnetic moments (M and m) decrease with the increase in lattice parameter. 4f electrons of Ho atom show the main contribution in magnetic moment.

First principles study of structure and property of Nb&lt;sup&gt;5+&lt;/sup&gt;-doped SrTiO&lt;sub&gt;3&lt;/sub&gt;

The modification of SrTiO&lt;sub&gt;3&lt;/sub&gt; materials by doping Nb&lt;sup&gt;5+&lt;/sup&gt; ions in B-site is studied through using the first-principles method to calculate the electronic structure, optical properties, mechanical properties and thermal properties at different Nb&lt;sup&gt;5+&lt;/sup&gt; doping concentrations. The calculation results show that as the doping content of Nb&lt;sup&gt;5+&lt;/sup&gt; increases, the lattice parameters increase. After being doped with Nb&lt;sup&gt;5+&lt;/sup&gt;, SrTiO&lt;sub&gt;3&lt;/sub&gt; changes from an indirect band gap compound into a direct band gap compound. Doping Nb&lt;sup&gt;5+&lt;/sup&gt; can reduce the reflection coefficient, absorption coefficient, and energy loss of SrTiO&lt;sub&gt;3 &lt;/sub&gt;material, which can be used to modify its optical properties. Additionally, the brittleness of SrTiO&lt;sub&gt;3 &lt;/sub&gt;material is improved through doping Nb&lt;sup&gt;5+&lt;/sup&gt;. As the doping content of Nb&lt;sup&gt;5+ &lt;/sup&gt;increases, the elastic modulus of the material hardly changes, the shear modulus and Young's modulus decrease, the Poisson's ratio increases, and the Debye temperature decreases, and both the lattice thermal conductivity and the theoretical minimum lattice thermal conductivity decrease as well.

Impact of Cd content on properties of Ni1-xCdxFe2O4 nanoferrites prepared without post-preparation thermal treatment

We report sol–gel auto-combustion synthesis of Ni1-xCdxFe2O4 (0.0–0.72) nano-ferrites (grain-diameter:13.8–28.6 nm) with no thermal-treatment and, its study by x-ray diffraction (XRD), scanning-electron-microscopy-energy-dispersive-x-ray-spectroscopy (SEM-EDS), vibration sample magnetometery, ultraviolet–visible (Uv–Vis) spectroscopic techniques. XRD, EDS confirm formation of spinel phase, with minor-presence of α-Fe2O3 phase. Results show linear increase of lattice parameter; strong compositional dependence of: cationic-distribution (Fe3+ Ni2+ ions more-populated on B-site, Cd2+ distributed on A, B site); inversion-degree; oxygen-parameter; very-similar mean-particle-agglomerate-size; variation of B-O-B A-O-B A-O-A super-exchange-interaction affect magnetic properties. Magnetism is governed by Yafet-Kittel three-sub-lattice model; studied samples remain in the overlap region between single/ multi-domain structures.

Remarkable bactericidal traits of a metal-ceramic composite coating elated by hierarchically structured surface.

SummaryA ceramic-based coating with a hierarchical surface structure was synthesized via solid-state reaction enabled by a double cathode glow discharge technique. This innovative coating comprises two distinct layers, specifically an outer layer with a well-aligned micro-pillar array and a dense inner layer. Both are composed of a face-centered cubic Cu(Co,Ni,Fe) solid solution phase together with a spinel-type Fe(Al,Cr)2O4 oxide. This coating exhibits superhydrophobicity and, yet, a very strong adhesion to water, i.e., the so-called “rose petal effect”. This coating also exhibits highly efficient antibacterial ability against both Staphylococcus aureus and Escherichia coli bacteria under both dark and visible light conditions. The excellent antibacterial property originates from the synergistic effects through the release of Cu ions coupled with photothermal activity upon light activation.

Characterization, spectroscopic investigation of defects by positron annihilation, and possible application of synthesized PbO nanoparticles* *Project supported by the University Grants Commission (UGC), New Delhi, India, for the departmental CAS scheme (No. F.530/5/CAS/2011(SAP-I)) and from the Department of Science and Technology (DST), Govt. of India under FIST (Fund for Improvement in Science & Technology) Program (Grant No. SR/FST/PS-II-001/2011).

Nanocrystalline samples of highly pure lead oxide were prepared by the sol-gel route of synthesis. X-ray diffraction and transmission electron microscopic techniques confirmed the nanocrystallinity of the samples, and the average sizes of the crystallites were found within 20 nm to 35 nm. The nanocrystallites exhibited specific anomalous properties, among which a prominent one is the increased lattice parameters and unit cell volumes. The optical band gaps also increased when the nanocrystallites became smaller in size. The latter aspect is attributable to the onset of quantum confinement effects, as seen in a few other metal oxide nanoparticles. Positron annihilation was employed to study the vacancy type defects, which were abundant in the samples and played crucial roles in modulating their properties. The defect concentrations were significantly larger in the samples of smaller crystallite sizes. The results suggested the feasibility of tailoring the properties of lead oxide nanocrystallites for technological applications, such as using lead oxide nanoparticles in batteries for better performance in discharge rate and resistance. It also provided the physical insight into the structural build-up process when crystallites were formed with a finite number of atoms, whose distributions were governed by the site stabilization energy.

Structural, optical and photoluminescence properties of TiO2 and TiO2: Tm3+ nanopowders

Tm3+-doped TiO2 nanocrystalline powders (in the range from 0.0 to 6 at. % of Tm3+) were synthesized by the sol-gel method at 500 °C. Structural, optical and photoluminescence properties were characterized by X-ray diffraction, transmission and scanning electron microscopy (TEM, SEM), UV–vis spectroscopy and photoluminescence spectroscopy. From XRD results all compositions show anatase structure, and the incorporation of Tm3+ promoted an increase in lattice parameters and inhibit the crystal growth. HRTEM micrographs show the presence of d-plane spacings corresponding to Tm2O3 and Tm2Ti2O7 phases for samples annealed at 500 °C. FTIR, reflectance UV–vis and photoluminescent spectra showed well defined bands ascribed to the Tm3+f-f transition. Vacuum referred binding energy diagram and chemical shift model approach are presented to analyze the relationship between the TiO2 electronic structure and the Tm3+f-f transition.

Study of Electrochemical and Crystallographic Changes During Initial Stabilization of La0.75Sr0.25Cr0.5Mn0.3Ni0.2O3−δ Reversible Solid Oxide Cell Electrode

AbstractThe electrochemical and crystalline structure of mixed ionic‐electronic conductive La0.75Sr0.25Cr0.5Mn0.3Ni0.2O3–δ (LSCMN) electrode in porous scandia ceria stabilized zirconia (ScCeSZ) electrolyte matrix during the first 140 h has been studied in an operando XRD experiment. Intense degradation of electrochemical performance in a fuel cell as well as in electrolysis modes has been observed. However, the mechanism of the degradation was seen to be different for the two operation modes. The formation of the new ceramic phase was observed on the surface of the electrode using the Grazing incidence X‐ray diffraction at the pulsed laser deposited LSCMN model electrode. Instability of the LSCMN phase in the ScCeSZ matrix at SOFC working conditions has been demonstrated using the novel operando XRD technique. The decrease in wt.% of the LSCMN during degradation was approximately 27 ± 4.5%. A slow increase of the ScCeSZ lattice parameter was observed and attributed to the doping of electrolytes with some LSCMN components.

Characterization of sol gel Zn1-xCaxO thin layers deposited on p-Si substrate by spin-coating method

Abstract Thin films Zn1-xCaxO (0 ≤ x ≤ 6%) on a p-Si substrate are elaborated by sol-gel process and spin coating. X-ray diffraction displays a hexagonal wurtzite structure with an increase of lattice parameters confirming the substitution of Zn2+ by Ca2+. The estimation of crystallite sizes along the three main crystallographic planes is practically constant (22 nm) suggesting a spherical symmetry shape of the crystallites which is confirmed by SEM. UV–visible reflectance spectra attest a band gap tuning from 3.144 to 3.262 eV which is confirmed by the PL measurement at 2 K for Zn0.94Ca0.06O sample by the appearance of a broad band around 3.508 eV. Although the luminescence of the samples is weak, we well distinguish the free exciton emission (FXA) positioned at 3.376 eV and the bound exciton recombination (D0X) around 3.362 eV.

Titanium Doped Barium Ferrite—A Case Study

In this paper synthesis of titanium doped barium ferrite (BaTixFe12–xO19) nanoparticles of hexagonal structure by employing sol-gel technique is reported. The composition was varied between x = 0.25 to 0.45. Structural analysis were carried out with the help of techniques such as X-ray diffraction (XRD) for phase identification, scanning electron microscopy (SEM) for morphological studies, to identify the elemental composition energy dispersive spectroscopy (EDX) was performed and Fourier transform infrared spectroscopy (FTIR) for bonding related information. From X-ray analysis it was observed that initially, with increase in Ti concentration there was a decrease in lattice parameters and cell volume. However, at Ti concentration of 0.38, an increase in lattice parameter was observed and has been attributed to electron hopping mechanism. Morphological analysis (SEM) done on the samples reveal that the nanoparticles are spherical in shape. EDX was utilized for elemental analysis of the products. FTIR spectroscopic studies reveal prominent peaks around 470 and 540 cm−1 is attributed to formation of ferrite structure and also indicative that the reaction is complete. The obtained results were discussed in the light of the available literature.

Influence of ZnO nanostructure configuration on tailoring the optical bandgap: Theory and experiment

Exploiting the link between form and function of semiconductor nanostructure provides a new prospect for tailoring the features of nanoscale materials. However, achieving this remains a challenge in the fabrication of optoelectronic devices. Therefore, this research systematically presents theoretical and experimental investigations of shape dependent structural and optical properties of ZnO nanostructures (nanoparticles, vertically oriented nanorods and compact ZnO) synthesized using the electroless deposition technique to understand the principles of bandgap modification. FESEM, XRD, Photoluminescence (PL) and UV–Vis spectroscopic characterizations were employed. The characterizations show increase in lattice parameters, bandgap and density of dislocations from 0.3236 nm to 0.3258 nm, ~3.14 eV to ~3.51 eV and ~17 × 10-4 to ~39 × 10-4, respectively as the ZnO nanostructures are transformed from compact ZnO to ZnO nanoparticles. The expansion in lattice parameter is attributed to lower compressive stress that exists in ZnO nanoparticles compared to compact ZnO. The blue shift (0.06 eV) in bandgap is ascribed to overlapping of the orbitals and energy level in ZnO nanoparticles which causes a substantial increase in energy gap between valence and conduction bands. The small size-induced hardening in ZnO nanoparticles accounts for their comparatively higher dislocation density. Theoretically, conversion from compact ZnO to ZnO nanoparticles extends the bandgap from 3.38 eV to 3.44 eV, which is consistent with the experimental results. This study confirms the shape dependency of the structure and bandgap of ZnO nanostructures, which may provide a new insight into future integrated optoelectronic device applications.

Temperature versus composition phase diagram and temperature evolution of structure and modulation of Ni2MnGa1-xInx single crystals

A series of single crystal Ni2MnGa1-xInx samples, varying in compositions between x = 0 to 0.15, were grown by Bridgman method. Critical temperatures were obtained from the magnetisation and electrical resistivity measurements. A Curie temperature and the temperatures of pre-martensitic and martensitic transformation decrease with increasing indium content. The decrease rate is faster than the rate published previously on polycrystalline samples, since no martensitic transformation was observed in our samples with the indium content x > 0.05. The results of X-ray diffraction measurements of low temperature martensitic phase show significant decrease of monoclinic lattice parameter a and increase of monoclinic lattice parameter c and γ angle with respect to increasing indium content. Composition dependence was observed also for the modulation vector in martensitic and pre-martensitic phase, where its x and y coordinates gain values around 3/7 and 1/3 respectively.

Thickness-Dependent Magnetism in Epitaxial SrFeO3-δ Thin Films

Strained oxygen-deficient perovskite SrFeO $_{3 - \delta }$ (SFO) films have been epitaxially grown by pulsed laser deposition (PLD) on SrTiO3 (STO) (001) substrates. Oxygen deficiency of the films in comparison with the stoichiometric perovskite SrFeO3 is manifested in the increased lattice parameter, $c = 3.97$ A, the decreased mass density, $\rho = 4.825$ gcm−3, and the presence of Fe3+ cations. The SFO perovskite structure is monoclinically distorted with an increase of the film thickness, resulting in the reduction of the total magnetic moment. A wasp-waisted hysteresis loop and a negative exchange bias are observed for the 69 nm thick film due to the possible magnetic sublayers arising from a proper monoclinically distorted surface layer and a substrate-locked core layer.

Effects of W and Si microadditions on microstructure and the strength of dilute precipitation-strengthened Al–Zr–Er alloys

The effect of single or combined micro-additions of tungsten (0.03 at.%) and silicon (0.02–0.40 at.%) on the evolution of Al3(Zr,Er) (L12) nanoprecipitates in a cast Al-0.11Zr-0.005Er (at.%) alloy is investigated utilizing isochronal (200–600 °C) and isothermal (400, 425 and 450 °C) aging treatments. Atom-probe tomography measurements reveal that the slow-diffusing W, upon aging, partitions to the L12-nanoprecipitates (average composition of 0.11–0.37 at.% W; partitioning ratio of 5–12), without altering their crystal structure or spheroidal morphology, as confirmed by transmission electron microscopy. First-principles calculations indicate that W occupies the Al sublattice sites of Al3Zr(L12), leading to a small increase in the lattice parameter of the nanoprecipitates. In the low-Si (0.02 at.%) alloys, the precipitation and coarsening kinetics of nanoprecipitates are unaffected by W additions. A small enhancement in nanoprecipitate coarsening resistance is achieved, however, by W additions in the high-Si (0.4 at.%) alloys. The W-modified alloys exhibit significant improvements in compressive creep resistance at 300 °C; the threshold stress increases from 11 MPa in the W-free alloy to 15 and 16 MPa in the low-Si and high-Si alloys with W additions, respectively. This is explained by an increased lattice parameter mismatch between the L12-nanoprecipitates and the matrix, due to Er enrichment in the nanoprecipitates in the presence of W. Silicon additions, in alloys with and without W, lead to a higher peak microhardness (ΔHV ~90–110 MPa) and higher creep threshold stresses (Δσth ~2–4 MPa) by increasing the L12-nanoprecipitate number density, but at the expense of their long-term coarsening resistance.

Theoretical and Experimental Investigation of Microwave Absorbing X-Type Hexaferrites Nanomaterial Synthesized by Cotton Soaked Method

In this article, Pr–Mn substituted X-type hexagonal ferrite Sr1–xPrxCu2MnyFe28–yO46 with concentrations of $x =0$ , 0.02, 0.06, 0.1 and $y =0$ , 0.1, 0.3, 0.5 were prepared by using cotton soaked method. The main intention of this article was to explain the microwave absorption phenomenon theoretically and to perceive the effect of Pr–Mn substitution on structural, magnetic, thermal, and microwave absorption properties of X-type hexagonal ferrites. Moreover, the fabrication of material suitable for microwave absorption devices, permanent magnets, and for recording media applications was also aimed in present investigation. The XRD patterns reveal that all the prepared samples possess X-type hexagonal structure. A gradual and slight increase in both lattice parameters “ $a$ ” and “ $c$ ” values was observed with Pr–Mn substitution. The metal–oxygen stretching (M–O) vibrations in the FTIR spectrum at a low frequency indicates the presence of single phase in synthesized material. The enhancement in magnetic properties (saturation magnetization, retentivity, and coercivity) has been observed with the substitution of Pr–Mn contents in pure ferrites. A maximum reflection loss (RL) of −27.21 dB at 11.891 GHz was attained by Pr–Mn-substituted ferrites and reflectivity results agree well with RL results. Microwave absorption property of this substituted material made it a potential candidate to be used in super high frequency (SHF) devices.