Decrease In Lattice Parameter Research Articles

Synthesis, characterizations and magnetic properties of nanoscale CoVxFe2-xO4 (0.0 ≤ x ≤ 0.9) materials synthesized via sol-gel autocombustion route

Nanostructured materials of CoVxFe2-xO4 (0.0 ≤ x ≤ 0.9) have been synthesized by sol-gel autocombustion method. Phase purity and nanocrystalline nature of the materials were examined by powder XRD measurements. Morphology and microstructure of the materials were ascertained by FESEM technique. The estimated crystallite sizes (d) decrease from 30 nm to 8 nm, as a result of progressive increase in V content, x, in CoVxFe2-xO4 materials. The values of the observed lattice parameters (a) decrease continuously as a function of increasing V content, x, i.e. from 8.349(5) Å to 8.284(5) Å for the values of x = 0.0 and x = 0.9, respectively. Alterations of M − O bond lengths in CoVxFe2-xO4 materials in FTIR studies indicate the incorporation of vanadium in cobalt ferrite. The values of the saturation magnetizations (Ms) and coercivities (Hc) of CoVxFe2-xO4 materials are found to be in the range of 77.58 emu/g – 37.76 emu/g and 1264 Oe – 991 Oe for various values of x from x = 0.0 to x = 0.9, respectively. The observed trends in magnetic parameters of CoVxFe2-xO4 materials have been interpreted on basis of increasing vanadium content in the materials, cation distributions, size and surface effects.

Enhanced dielectric and magnetic properties of magnetodielectric La2−xPrxCoMnO6 for spintronic applications

La2−xPrxCoMnO6 (x = 0.5, 1.0, 1.5 and 2.0) double perovskites were prepared via sol gel method. X-ray diffraction peak profile inveterate the nonexistence of impurity phases in the prepared system. Rietveld refinement suggested that ordered monoclinic (P21/n) phase exist along with disordered orthorhombic (Pbnm) and rhombohedral (R3c) structural phases. A decrease in unit cell volume and lattice parameters is observed with increase in Pr content which is in agreement with the difference in ionic radii of La and Pr ions. Morphological and compositional study using FESEM with EDX suggested that grain size lies in micrometer range and signifies the purity of developed samples. Dielectric constant as well as tangent loss exhibit dispersive behavior at lower frequencies and higher temperatures. The strong effect of bond angle, anti-site disorder and grain size is observed on dielectric properties. Due to large bond angle and large antisite disorder, LPCMO2 exhibited largest value of dielectric constant among all developed compositions. Cole-Cole plots proposed a non-Debye type relaxation and indicated NTCR (negative temperature coefficient of resistance) behavior for the synthesized compositions. Ac conductivity showed increasing tendency with rise in both frequency as well as temperature. Increase in dc conductivity with temperature proposed semiconducting behavior of prepared samples that can be explained on the basis of Thermal activation (TA) and Variable range hopping (VRH) models. The saturation magnetization (Ms) showed a strong correlation with bond angle, tilting of CoO6/MnO6 octahedra and grain size i.e. LPCMO2 is having largest Ms whereas lowest Ms is exhibited by LPCMO3 which may be due to variation in exchange interaction which strictly depends on bond angle and tilting of MO6 octahedra. Enhanced magnetic properties make these materials useful for spintronic devices and magnetic storage. Dielectric and magnetic properties of the prepared samples depend strongly on ˂Co-O-Mn˃ bond angle and have same variation tendency with Pr substitution which indicates coupling between these properties.

Evolution of structural-phase state and properties of hypereutectoid steel rails at long-term operation

The methods of modern physical materials science were used to analyze the evolution of microhardness, tribological properties, dislocation substructure and phase composition of the rails with increased wear resistance and contact endurance of DT 400 IR category after missed tonnage of 187 million gross tons on the experimental ring of Russian Railways. It is shown that extremely long-term operation of the rails is accompanied by a decrease (3.1 times) in wear parameter of the rolling surface and an increase (1.4 times) in microhardness, scalar dislocation density (1.5 times) and Fe3C carbide content (1.24 times). Operation of the rails led to a decrease in the crystal lattice parameter, which correlates with an increase in the content of iron carbide. We made the assumptions about physical causes of the change in parameters.

Influence of synthetic temperature on structural and magnetic properties of Dy substituted Ni nanoferrite

ABSTRACT Dy substituted Ni ferrite nanoparticles with composition NiFe1.95Dy0.05O4 were synthesized by using the citric acid sol–gel auto combustion method. The samples were sintered at temperatures of 400°C, 700°C, and 900°C. The X-ray diffraction measurements clearly showed the formation of a cubic spinel structure along with a small orthoferrite phase for all the sintered samples. The crystallite size increases from 17.79 to 39.36 nm while the grain size increases from 50.70 nm to 83.05 nm. The lattice parameter and lattice volume decrease with increasing sintering temperature was observed. The Spinel ferrite structure of prepared samples has been confirmed from FTIR spectra. With increasing sintering temperature saturation magnetization increases from 25.80 emu/gm to 49.48 emu/gm while the coercivity value decreases from 207.95 Oe to 165.43 Oe. Increasing saturation magnetization and decreasing coercivity values with increasing sintering temperature make the synthesized nanoparticles suitable for high-density data storage devices.

Electroacoustic Effect and Electrical Superconductivity of Metals

The paper discusses the conditions under which superconductivity of metals would be detected at atmospheric pressure and at room temperature. One of the possible directions of research to achieve these conditions is to change the phonon spectrum of metals in order to increase the Debye temperature, and therefore to increase the temperature of the superconducting transition Tc. According to the idea of the work and to the estimates made in it, the maximum frequency of phonons nmax in metals can be increased by the short-term action of an external constant electric field (electric pulse). The duration of the pulse should be (10–5–10–7) s. The voltage of the constant electric field source is U » 1V. A decrease in the crystal lattice parameter should be accompanied by an increase in the maximum phonon frequency nmax and, accordingly, by an increase in the Debye temperature. The characteristic size of the sample, in which the change in electron concentration can be realized, should not exceed the length of electron shielding in metals, i. e. ≈ 10–8 m. The sequential action of a certain number of electric field pulses can maintain a superconducting state in a metal sample for some finite time.

Mössbauer and X-ray Studies of Radiation-Induced Processes in Nb-Zr Alloys Implanted with 57Fe Ions.

The effect of implanting 57Fe ions on the crystal structure of Nb-Zr alloys has been studied using Mössbauer spectroscopy on 57Fe nuclei and X-ray diffraction. As a result of implantation, a metastable structure was formed in the Nb-Zr alloy. The XRD data indicated a decrease in the crystal lattice parameter of niobium; that is, there was a compression of the niobium planes when implanted with iron ions. Mössbauer spectroscopy revealed three states of iron. The singlet indicated a supersaturated Nb(Fe) solid solution; the doublets characterized the diffusion migration of atomic planes and crystallization of voids. It was shown that the values of the isomer shifts in all three states did not depend on the implantation energy, which indicates the invariance of the electron density on the 57Fe nuclei in the studied samples. The resonance lines of the Mössbauer spectra were significantly broadened, which is typical for materials with low crystallinity and a metastable structure that is stable at room temperature. The paper discusses the mechanism of radiation-induced and thermal transformations in the Nb-Zr alloy, which leads to the formation of a stable well-crystallized structure. A Fe2Nb intermetallic compound and the Nb(Fe) solid solution formed in its near-surface layer, while Nb(Zr) remained in the bulk.

Phase evolution in the UO2–CeO2 system under oxidizing and reducing conditions: X-ray diffraction and spectroscopic studies

The solid-solution formation mechanism and defect dynamics in U1-xCexO2±δ solid solutions have been investigated by means of X-ray diffraction (XRD) analysis, Raman spectroscopy, and X-ray absorption near-edge structure (XANES) spectroscopy. Diffraction studies have revealed the formation of single-phase solid solutions with a fluorite-type structure at x ≤ 0.2 and a single-phase fluorite-type structure with broadened diffraction peaks, attributed to inhomogeneity in the O/M ratio, at 0.3 ≤ x ≤ 0.8 under reducing conditions. Oxidizing conditions result in the formation of single-phase solid solutions with fluorite-type structure at x ≥ 0.4. Upon the formation of Ce3+ in solid solutions at x ≤ 0.2 under reducing conditions, charge neutrality is achieved through oxygen vacancy creation and formation of higher oxidation states of uranium through a charge compensation mechanism. Lattice parameter–composition relationships for fluorite-type phases synthesized under oxidizing conditions show a decrease in lattice parameters as compared to their stoichiometric counterparts due to the oxidation of U4+ to U5+/U6+. XANES studies provide direct experimental evidence of the presence of Ce3+ in solid solutions, despite synthesis under oxidizing conditions.

Investigation of Physiochemical Impact of Organic Molecule L-Lysine on Ammonium Dihydrogen Phosphate Single Crystal for Optoelectronics Applications

Ammonium dihydrogen phosphate (ADP) single crystals along with the incorporated 0.5 and 1% L-lysine, an organic molecule which possesses a good nonlinear response, were grown with the vision to meet the requirements of the optoelectronic industry. The inclusion of the L-lysine molecule in the crystal was confirmed by the XRD and EDX. The experiment not only confirms the inclusion level of the impurity but also the capability of the amino acid molecule to bond hydrogen within the crystal facet. A minor decrease in lattice parameters was reported for all ADP: L-lysine crystals compared with pure ADP. The structures of the grown crystals were identified as tetragonal with the space group I42d by the single-crystal XRD analysis. Vibrational signatures and functional groups were confirmed using FTIR spectroscopy. The thermal stability and decomposition temperatures of 0.5 and 1% L-lysine-added crystals were measured by TG/DTA and found to be 203 °C and 207 °C, respectively. The UV–visible transmission spectra prove a higher transparency for doped crystals as compared to pure crystals; therefore, these doped crystals can be considered the best option for the frequency doubling process in a broad range of visible and near-IR spectra. The improved hardness of the doped crystals was confirmed by the Vickers hardness data. The nonlinear optical (NLO) behaviour investigated using a second-harmonic generation (SHG) technique, indicating an efficient quadratic nonlinear coefficient of ADP: Lysine crystals at a 1064 nm initial wavelength, shows about 1.5-fold higher efficiency compared with undoped ADP.

Photodegradation of methylene blue dye using light driven photocatalyst-green cobalt doped cadmium ferrite nanoparticles as antibacterial agents

A cobalt-doped cadmium ferrite nanoparticle (CoxCd1-xFe2O4; x = 0, 0.2, 0.4, 0.6, 0.8, 1) was synthesized using curd as fuel during combustion. The symphonized nanoparticle's crystalline structure, size, morphology, photoluminescence, and optical properties are analyzed using PXRD, FTIR, SEM, HRTEM, XPS, UV–visible, and photoluminescence spectroscopies. PXRD analysis indicates that synthesized nanoparticles have a cubic spinel structure and that as cobalt doping increases, crystalline size and the lattice parameter decrease. FTIR analysis confirms tetrahedral and octahedral sites for vibrational stretching modes. Further SEM and HRTEM analyses reveal the morphology of the synthesized nanoparticles, which are agglomerated and have a nanoflakes-like structure. Furthermore, X-ray photoelectron spectroscopy reveals the elemental composition, oxidation, and transition states of CDCF NPs. UV–Vis spectroscopy discloses absorption, band gap regarding prepared NPs, and band gap deductions with increased cadmium substitution. The effect of cadmium substitution on luminescence is demonstrated by photoluminescence spectroscopy. Under visible light, photodegradation of the dye Methylene Blue in the presence of photocatalyst CDCF nanoparticles indicates that Co0.4Cd0.6Fe2O4 has higher degradation activity than other NPs. Antibacterial activity was performed for Gram-positive (S. aureus) and Gram-negative (Shigella) in the presence of synthesized Nano-particles. Activity results revealed that Co0.6Cd0.4Fe2O4 and CO0.2Cd0.8Fe2O4 NPs show an excellent zone of inhibition for S. aureus and Shigella bacterial strains.

Phase relations and lattice parameter trends in Nd3+−substituted UO2 system under reducing and oxidizing conditions

While Am-substituted UO2 solid solutions have been considered as advanced fuels for heterogeneous transmutation of americium, U-substituted Am2O3 with cubic structure has been envisaged as a promising candidate for radioisotope heat unit and radioisotope thermoelectric generator. Considering Nd2O3 as a surrogate for Am2O3, a series of Nd3+-substituted UO2 samples with the general formula U1-xNdxO2±δ (0 ≤ x ≤ 1, δ ≥ 0) have been investigated for phase relations under reducing and oxidizing conditions. In this direction, samples have been synthesized by a solid-state route and thoroughly characterized by X-ray diffraction and Raman spectroscopy. XRD studies revealed the formation of fluorite-type solid solution at x ≤ 0.7 and a biphasic phase field consisting of C-type (U,Nd)O2−δ phase and A-type Nd2O3 at x ≥ 0.8 in reducing conditions. In the fluorite-type regime, due to the aliovalent Nd3+-substitution in UO2, the charge neutrality was achieved primarily through oxygen vacancy creation as evident from lattice parameter trends as well as Raman spectroscopic investigation that exhibit Raman band due to oxygen vacancies. The reduced samples have a high tendency to get oxidized even during storage under ambient conditions leading to a decrease in lattice parameters, which can be attributed to the formation of the higher oxidation state of uranium (U5+/U6+) following a charge compensation mechanism. Synthesis in the oxidizing conditions yielded a biphasic phase field at x ≤ 0.2, a single-phase fluorite-type phase field at 0.3 ≤ x ≤ 0.7, a biphasic mixture of fluorite-type (U,Nd)O2−δ and trigonal Nd6UO12 phases at x = 0.8 and another biphasic mixture of Nd6UO12 and Nd2O3 phases at x = 0.9. The transition of reduced single-phase fluorite-type solid solution at x ≤ 0.2 to a biphasic mixture upon oxidation has been probed by a high-temperature XRD.

Crystal structure and magnetic property correlations in Ba1−x Sr x Fe12O19 (0 ≤ x ≤ 1) hexaferrites

This paper reports a comprehensive study on the structure-property correlations in strontium-substituted barium hexaferrite and their suitability for possible applications at room temperature. A series of samples, Ba1−x Sr x Fe12O19 (0 ≤ x ≤ 1) synthesized by citrate-based sol-gel auto-combustion technique, were characterized by various physicochemical characterization techniques. The x-ray diffraction data of these samples ensure the single-phase formation and the variation of crystallographic parameters as a function of strontium substitution was discussed. The decrease in lattice parameters with increasing strontium (x) substitution ensures the applicability of Vegard’s law for the present system. The scanning electron micrographs reveal some of the grains in hexagonal shape in these samples. Raman data revealed the interconnection between magnetic ion site occupancies and the corresponding magnetization contributions, thereby ensuring the structure-property correlations in these samples. As these hexaferrites consist of layers of (ferro- and antiferro-) magnetic domains, the sub-lattice magnetic contributions were estimated by fitting the magnetic hysteresis loops (M − H) data using theoretical models. The magnetization versus temperature (M − T) graphs confirmed the above room-temperature ferromagnetic behavior. This study clearly reveals that proper tuning of their structural properties can result in optimal magnetic properties, making them suitable for permanent magnet and room-temperature magnetic device applications.

Effects of milling time on the microstructure and properties of FeCoNiMnAl magnetic high-entropy alloys

FeCoNiMnAl magnetic high-entropy alloys (HEAs) were prepared by mechanical alloying and spark plasma sintering (SPS). The effects of milling time on the microstructure evolution, hardness, compressive strength, and magnetic properties of FeCoNiMnAl HEAs including powders and sintered bodies were investigated. After 30 h of milling, the HEA powders formed a solid solution with predominately face-centered cubic (FCC) phase structure and a small amount of body-centered cubic (BCC) phase. With a further increase in milling time, the BCC phase was transformed into the FCC phase. In the course of the BCC-to-FCC transformation, the hardness and compressive strength noticeably increased, while the magnetic properties of the alloys slightly decreased. Moreover, the decrease in lattice parameter of the FCC phase was shown to be an important factor enhancing the magnetic properties of HEAs. Besides, the high saturation magnetization of 84.7 emug was achieved in HEA-4. The maximum hardness and compressive strength of the samples were found to be 577 HV and 2099 MPa, respectively.

The Effect of Annealing Temperature on the Structural and Magnetic Properties of Lanthanum Doped Cobalt Ferrite with the Bengawan Solo River Fine Sediment as the Source of Fe<sup>3+</sup>

The effect of annealing temperature on the structural and magnetic properties of a rare earth (La3+) doped cobalt ferrite with fine sediment from the Bengawan Solo River as the source of Fe3+ has been studied. Co-presipitation method is use for preparation nanoparticles whole this experiment. In order to modified the physical properties, the annealing treatment of 2000C, 3000C, and 4000C are performed. The obtained nanoparticles are characterized their structural properties by using X-ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. Then, magnetic properties evaluated by using Vibrating Sample Magnetometer (VSM). XRD results have shown that there is an increase in crystallite size with an increase in the given annealing temperature from 24.56 nm to 27.83 nm. The increase in crystallite size can be attributed to the increase in the internal energy of the crystal structure which promotes atomic diffusion. Meanwhile, there is a decrease in the value of the lattice parameter with an increase in the given annealing temperature. The decrease in lattice parameters with increasing crystallite size is generally due to the lattice parameters reaching a minimum energy with increasing crystallite size. The formation of La3+-O2- for the incorporation of rare earth ions into the lattice requires high energy. The FTIR results show an absorption that appears at the peak around ~580 cm-1. This indicates that the La3+ cation has successfully replaced the original structure of cobalt ferrite. The VSM results show that there is an increase in the value of Hc with an increase in the annealing temperature given from 100 Oe to 160 Oe. This is supported by the increase of anisotropy constant and increasing temperature annealing.

Addition Effects of MgO‏ on Structure and Physical Properties in Bi-2212 Ceramics

The effect of magnesium on the microstructural and superconducting characteristics of bulk Bi2Sr2CaCu2MgxOy superconductors with x=0 to 0.05 by solid reaction has been examined in this study. Bi2Sr2CaCu2O8+d is formed as the primary phase, and Bi2Sr2CuO6+d (Bi-2201) is present as the parasitic phase, according to XRD data. In doped samples, the c lattice parameter decreases, indicating that Mg has entered the Bi2Sr2CaCu2O8+d crystallographic unit cell. The grain morphology of the samples containing magnesium has changed significantly, and the lamellar structure typical of high temperature superconductors can be seen in the SEM micrographs. The critical temperatures, Tcoff and Tconset, are raised by the addition of Mg, delimiting the superconductive transition. Tconset's maximum value corresponds to x = 0.05.

Sputter Deposited Mn‐doped ZnO Thin Film for Resistive Memory Applications

AbstractTransition metal doped Zinc oxide (ZnO) thin films with wide band gap semiconducting nature have diverse range of applications including, gas sensors, optical and optoelectronic devices, electronics and spintronics spintronic devices etc. In the present study, Manganese (Mn)‐doped ZnO thin films deposited on glass substrates using RF‐magnetron sputtering have been investigated for their optical and electrical behavior aiming at resistive random access memory applications. To study the influence of Mn doping and correlation between the structural and the physical properties of the films, the samples were characterized by X‐ray Diffraction (XRD), Raman spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X‐ray Spectroscopy (EDS), UV‐VIS spectrophotometry and X‐ray photoelectron spectroscopy (XPS). The films are found to be crystalline and a decrease in lattice parameter from 2.6049 Å to 2.5845 Å, an increase in optical band gap from 3.27 eV to 3.35 eV and a decrease in Urbach energy from 0.222 eV to 0.171 eV, is observed with increase in Mn‐concentration. The electrical performance of the film with highest Mn‐content is found to be more suitable for resistive memory applications. Tailoring the electrical behavior of the film by incorporating Mn as dopant is an important approach to find suitable material combination for novel memory devices.

Multiphase zinc and magnesium mono-substituted calcium phosphates derived from cuttlefish bone: A multifunctional biomaterials

Biomimetic calcium phosphate (CaP) systems mono-substituted with zinc (Zn2+) and magnesium (Mg2+) ions were prepared from a biogenic source (cuttlefish bone) by wet precipitation method. The results revealed that the as-prepared powders were composed of calcium-deficient carbonated hydroxyapatite (HAp), octacalcium phosphate (OCP), and amorphous calcium phosphate (ACP), while the heat-treated powders consisted of HAp, α-tricalcium phosphate (α-TCP), and β-tricalcium phosphate (β-TCP). In addition to Zn2+ and Mg2+ ions, the presence of CO32−, Sr2+ and Na + ions was detected with elemental analysis, which can be attributed to the use of cuttlefish bone as a natural precursor of Ca2+ ions. The data obtained by XRD study demonstrated the decrease in lattice parameters in the OCP and β-TCP phases for Zn-substitution and Mg-substitution in the HAp, OCP, and β-TCP phases. Zn2+ occupies the Ca(1,3,4,6,7,8) sites in OCP and Ca(1,2,3,4) sites in β-TCP, while Mg2+ occupies the Ca(2) sites in HAp and the Ca(4,5) sites in β-TCP. Phase transformation study under simulated physiological conditions for 7 days showed the transformation of OCP and ACP into the thermodynamically more stable HAp. Characterization of the zeta-potential showed positively charged populations for all prepared CaP powders, while all samples showed high bovine serum albumin adsorption capacity. The culture of human embryonic kidney cells showed that the prepared CaPs are non-cytotoxic and that viability of the cells increases during the culture period. All powders obtained showed antibacterial activity towards Gram-negative Escherichia coli and low antibacterial effect against Gram-positive Staphylococcus aureus, as determined by viability analysis during 48 h. Inhibition zone analysis and observation of the morphology after 24 h showed no antibacterial properties.

Uncovering the Effect of Al Addition on the Hydrogen Storage Properties of the Ternary TiVNb Alloy.

The effect of Al addition on the structure, microstructure and hydrogen storage properties of the ternary TiVNb alloy was investigated from small amounts to equimolar composition. Alx(TiVNb)1-x (x = 0.05, 0.175 and 0.25) alloys are bcc single-phase materials with decreasing lattice parameters with increasing Al content. Al addition progressively decreases the hydrogen storage capacity but also destabilizes fcc dihydride formation for alloys with x ≤ 0.10. Among the different compositions, the most promising alloy was found to be that with x = 0.05 Al content that exhibited high initial storage capacity (2.96 wt.%), a less stable hydride (ΔH = -52 kJ/mol H2 and ΔS = -141 J/K∙mol H2), better desorption properties (desorption onset temperature around 100 °C) and enhanced reversible capacity during cycling (2.83 wt.%) compared to the ternary TiVNb. In situ and ex situ synchrotron X-ray powder diffraction, together with thermal desorption experiments, showed improved desorption properties with Al addition, together with a two-step reaction with hydrogen. These findings highlight the use of small quantities of lightweight Al in refractory multi-principal element alloys as a promising approach for enhancing the solid-state hydrogen storage performance of bcc-type alloys.

Effect of Ni2+ substitution on structural, magnetic and electrical traits of Ba1-xNixFe2O4

Nickel substituted Barium ferrites is synthesized by citrate gel method. Nickel which is transition metal used to tailor the properties of the Ba spinel ferrites. The characterization techniques such as thermogravimetry–differential thermal analysis (TG-DTA), X-ray diffraction (XRD), vibrating sample magnetometry (VSM), Fourier transform infrared spectroscopy (FTIR), ultra-violet diffuse-reflectance spectroscopy (UV-DRS), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM), Raman analysis and direct current (DC) electrical conductivity are used to investigate various properties. XRD and rietveld refinement confirmed the existence of orthorhombic as well as cubic phase with the decrease in lattice parameters in orthorhombic phase. FTIR spectra confirmed the presence of absorption bands for tetrahedral and octahedral sites. Tauc’s plots accredited the increase in band gap with increase in Ni content. The magnetic hysterisis loop exhibited large variation in coercivity and remanence. Increased Yafet-Kittel (Y-K) angle indicated redistribution of ions amongst the sites strenthening the A-B exchange interactions. DC electrical conductivity observed the conductive switching from n-type to p-type. Thermally activated charge carriers and hopping of electrons boost drift mobility. The activation energy of conduction is observed in the range of 0.40 to 0.85 eV. Raman peaks confirmed formation of orthorhombic as well as cubic phase.

The crystallographic structure and properties of novel quaternary nanolaminated rare-earth-Cr-based i-MAX phases

Seven novel inherently nanolaminated transition metal carbides, (Cr2/3R1/3)2AlC (R = Gd, Tb, Dy, Ho, Er, Tm, Lu) with R in-plane chemical ordering in the carbide sheet, have been synthesized and found to be crystallized in Cmcm orthorhombic structure with monotonously decreased lattice parameters due to lanthanides constrictions. Linear antiferromagnetism is found for R = Gd and gradually changed to paramagnetism for R = Er, Tm and Lu through nonlinear magnetic configurations with gradually decreased ordering temperature. Compared with Cr2AlC benchmark, the Vickers hardness is significantly higher, leading to higher compressive fracture strength and better wear resistance. After compression at high temperature, nanoscale co-existence of the C2/c monoclinic and orthorhombic structure is observed, which is caused by the random stackings and high-density slidings within ab plane. The further first-principle calculations confirm the close thermal stability of both two structures.

Synthesis of a magnetically removable visible-light photocatalyst based on nickel-doped zinc ferrite

In this study, a facile method to synthesize magnetically removable visible-light photocatalysts based on nickel-doped zinc ferrites is presented. Ferrite semiconductor ceramics with the general formula Zn1-xNixFe2O4 (0 ≤ x ≤ 0.5, Δx = 0.1) were prepared by high-energy ball milling followed by annealing at 873 K. X-ray diffraction analysis confirmed the spinel single-phase Fd-3m without secondary phases for all compositions. The slight decrease in lattice parameters confirmed the presence of Ni2+ ions in the crystal structure because Ni had a smaller ionic radius than Zn. Raman spectroscopy demonstrated that Ni2+ ions were distributed on both tetrahedral and octahedral sites, which increased the inversion parameter and affected the photocatalytic efficiency and ferromagnetism. Magnetic hysteresis loops suggested an increase in the specific magnetization as the doping content increased, enabling magnetic recovery and reuse of the photocatalyst in water remediation. Diffuse reflectance spectroscopy showed a reduction in the band gap values with increasing nickel content, which was attributed to forming a sub-level in the band structure in the presence of Ni2+. Photocatalytic tests revealed a degradation efficiency higher than 60%, confirming that the doped samples obtained by high-energy ball milling were highly efficient and easily removable photocatalytic materials.