Increase In Lattice Parameter Research Articles

Structural, Spectral, XPS and Microwave Absorbing Properties of Ba0.5Sr0.5Zr2Fe4-xNdxO11 R-type Hexaferrites

Ba0.5Sr0.5Zr2Fe4-xNdxO11 (x = 0.00, 0.03, 0.06, 0.09) hexaferrites have been developed using Sol-gel methodology. Structural, elemental, and dielectric characteristics of synthesized hexaferrites were identified. The materials had a single phase corresponding to XRD graphs. The 'c' lattice parameter increases and 'a' decreases due to lattice distortion and internal stresses because substituted element ionic radii Nd3+ (1.12 Å) are higher than those of Fe3+ (0.64 Å). Calculated crystallite sizes of Nd3+ substituted R-type hexagonal ferrites are found to be among 14.4859- 11.7120 nm. According to Fourier-transform infrared spectra, the Fe-O bond exists at octahedral and tetrahedral sites. Modifications in band locations occurred when the content of Nd3+ was substituted. It is noticed that two force constants (Kt and Ko) are increased by the addition of Nd3+, confirming powerful intermolecular bonding. When multiple dielectric attributes were investigated in the frequency range 1 GHz-6 GHz, it was determined that both frequency and inclusion of Nd3+ altered all parameters. Tan loss, dielectric constant, ac conductivity, and dielectric loss factor displayed a growing trend, although both decrease as frequency rises. The existence of every metal ion with its corresponding electronic state was verified by X-ray photoelectron spectroscopy (XPS) data. The materials exhibit decreasing Q values and are used to construct resonant filters. The synthesized materials may be used in storage media, microwave frequency attenuation devices, GHz recording, refrigerator magnets, and electrical components in mobile phones.

Effect of chemical segregation on accuracy of local lattice distortions determination by pair distribution functions

Local lattice distortion (LLD) is a salient feature of bcc-structured refractory high-entropy alloys (RHEAs), closely associated with their mechanical properties. To quantify the extent of LLDs in RHEAs, the pair distribution function (PDF) analysis has been identified as a promising approach. However, the commonly observed chemical segregation within these alloys introduces challenges in accurately determining LLDs. In this study, the effect of chemical segregation on LLD quantification was investigated through fitting simulated two-phase composite PDFs, representing segregated microstructures, with a single-phase model and evaluating the errors to assess the accuracy and reliability of small-box analysis in this context. The results show that the errors introduced by chemical segregation increase with increasing lattice parameter difference, and the fitting quality gradually deteriorates to a point where it no longer adequately describes the data. We found that the lattice parameter difference should be below 1% for precise and reliable LLD measurements in bcc-structured RHEAs. Additionally, we observed that while the scattering length variation due to segregation does affect LLD quantification, its effect is comparatively minor.

Effects of synthesis temperature on the structural and optical properties of CaAl2O4: Eu2+, Dy3+nanoparticles

Calcium aluminate phosphor nanomaterials co-doped with europium and dysprosium (CaAl2O4: Eu2+, Dy3+) were prepared using a facile solution combustion technique. The structural and optical properties were investigated. The X-ray diffraction (XRD) results confirmed the presence of the monoclinic phase in all the samples, with few impurity phases in the samples synthesized at 300 °C and 400 °C. The Fourier-transform infrared analysis gave the expected chemical combustion results of the final product with few traces of Ca3Al2O6 impurities at low and very high synthesis temperatures. The XRD patterns displayed diffraction angles of the major peaks shifting to higher 2 theta as the synthesis temperature increased. This is attributed to an increase in particle sizes, which led to an increase in lattice parameters. The intensity of the prominent peak increased up to 500 °C due to improved crystal quality. The crystallite sizes of the as-prepared samples were determined using the Debye-Scherrer equation. It was noted that there is variation in the crystallite sizes with synthesis temperature. The UV–Vis graph shows that absorption edges also shifted to lower wavelengths with an increase in synthesis temperature. It was noted that the band gap increased with an increase in synthesis temperature up to 500 °C, but at temperature of 1000 °C, the band gap was observed todecrease. Scanning electron microscope micrographs showed that the samples had irregular shapes with pores and cracks. The study provides a simple route to synthesize CaAl2O4: Eu2+, Dy3+phosphors with optimum synthesis temperature, producing the most crystalline sample for use in lighting devices.

Study of structural, dielectric properties of ZnFe2O4: effect of thermal annealing

Abstract We report structural, dielectric properties of sol-gel auto-combustion-synthesized ZnFe2O4 nano-ferrites (grain-size: 53.43 - 64.81 nm), and study the effect of thermal annealing on structural dielectric properties by X-ray diffraction (XRD), dielectric measurements. Results show that thermal-annealing shows: i) an increase of lattice parameter (aexp.), and on B-site: there is an increase of Zn2+ population with concurrent decrease of Fe3+ ions, ii) alterations of inversion-degree from 0.18 to 0.32, strengthening of A-O-B, A-O-A interactions, accompanied by a weakening of B-O-B super-exchange-interaction, iii) decrease of theoretical magnetization at 0 K (Ms(th)), iv) with increasing frequency, real-imaginary components (ε', ε'') of dielectric constant, and loss-tangent decreases, v) that at higher frequencies, ac conductivity (σac) shows a significant increase and exhibited a power law dependence, suggesting a typical of charge transport assisted by a hopping or tunneling processes. Results also reveal that polarizability strength decrease with annealing temperature, and correlated-barrier-hopping remains the dominant mechanism for conduction. Cole-Cole plots (ε', ε''), corresponding complex impedance (Z', Z'') data are indicative of the growing influence of grain boundaries on the dielectric properties for the studied samples. Observed improved-response of σac, recommends the potential-applications of the studied samples in high-frequency device applications.

Novel proton-conducting hexagonal perovskites Ba7In6–xYxAl2O19 for solid oxide fuel cells

The solid solution Ba7In6–xYxAl2O19 (0≤x≤0.25) with a hexagonal perovskite-like structure was prepared by the solid-state route. The introduction of yttrium was accompanied by an increase in lattice parameters. The total conductivity as a function of pO2 and T was measured at different humidity. The partial conductivities were found by transport number measurements and were fitted based on the defect formation model. Oxygen-ion and proton conductivities were found to increase with Y3+ content as a result of an increase in cell volume and free volume, which was accompanied by a decrease in the activation energy of both oxygen-ion and proton conductivity. Oxygen-ion conductivity and proton conductivity dominated below 500 °C in dry (pH2O=3.5×10−5 atm) and in wet (pH2O=1.92×10−2 atm) conditions, respectively. Doping makes it possible to increase proton conductivity by an order of magnitude (500 °C) and significantly increase the proton transport numbers.The prepared phases exhibited excellent chemical stability during thermal treatment in carbon dioxide (pCO2=1 atm).

Structural distortion-induced low-temperature dielectric dispersion in lanthanide titanate pyrochlores

Rare-earth titanate pyrochlores have attracted significant attention for their unique magnetic frustration; however, research on the origin of low-temperature dielectric dispersion and the relationship between dielectric properties and structure lags far behind. Here, by systematically investigating the dielectric properties of representative rare-earth titanates R2Ti2O7 (R = La, Nd, Sm, Er, Yb, and Lu), we demonstrate that R2Ti2O7 with a cubic pyrochlore structure exhibits low-temperature dielectric dispersion behavior, while the other compounds with a monoclinic perovskite-like layered structure possess no dispersion behavior but excellent temperature-stable dielectric property. The dielectric dispersion in cubic pyrochlores arises from the structural distortion. Furthermore, the existence of structural distortion is affirmed by the anomalous phonon softening of A1g Raman mode around the dielectric dispersion temperature, and the origin of the structural distortion is attributed to anharmonic phonon–phonon interactions induced by intrinsic vacant oxygen at Wyckoff 8a sites. In addition, with increasing ionic radius from R = Lu to Sm, the increased lattice parameter leads to varied bond length and bond angle of Ti-O(1)-Ti, which strengthens the local lattice distortion of TiO(1)6 octahedra and thus enhances diffusion degree of dielectric dispersion. On the other hand, the absence of intrinsic vacant oxygen site hardly gives rise to the local structural distortion and thus no dielectric dispersion in monoclinic R2Ti2O7. Our work not only clarifies the mechanism of dielectric dispersion but also gives a comprehensive perspective on the structure–property relationship of rare-earth titanates R2Ti2O7, and thus lays a solid foundation for further work on related materials.

Structure and properties analysis of yttrium doped high-voltage LiNi0.5Mn1.5O4 cathode materials for Li-ion batteries

High voltage cathode spinel material of LiNi0.5Mn1.5O4 was doped by yttrium (Y) element in the form of LiNi0.5Mn1.5−x Y x O4 (x = 0, 0.05, 0.1) for Li-ion batteries. Structure and properties analysis was conducted to study the effect of Y addition on the crystal structure and the electrochemical performances of LiNi0.5Mn1.5−x Y x O4. The results show that undoped LiNi0.5-Mn1.5O4 (x = 0) fit to cubic spinel structure with space group Fd-3m with some LixNi1-xO detected as impurities. The addition of Y with x = 0.05 and 0.1 resulted in the change of LiNi0.5Mn1.5−x Y x O4 structure to space group P4 332. The Y addition was confirmed to enter 4b site co-existed with Mn and this result is closely related to the increase in lattice parameters a from 8.1384(1) Å to 8.1496(5) Å and 8.1627(1) for x = 0, 0.05 and 0.1, respectively. The cubic unit volume of LiNi0.5Mn1.5−x Y x O4 also increased with increasing Y addition. The addition of Y is liable to the formation of more stable [Mn,Y]O6 and MnO6 octahedra and whole crystal structure. The result from charge/discharge analysis shows that the addition of Y resulted in decreasing discharge capacity from 123.56 mAh g−1 to 105.175 mAh g−1 and 104.369 for x = 0.05 and 0.1, respectively. However, capacity retention after the 25th cycle increased constantly from 77% to 88% and 92% with increasing Y addition. Doped Y, in general, improves the electrochemical performance of LiNi0.5Mn1.5−x Y x O4 as cathode material for LIBs.

NASICON-type medium entropy Li1.5Sn1.0Al0.5Zr0.5(PO4)3 electrolyte for solid state Li metal batteries

Developing solid electrolytes for all-solid-state lithium batteries with superior performance is crucial for portable energy storage. This study uses a traditional solid-state reaction technique to fabricate a NASICON-type medium entropy Li1.5Sn1.0Al0.5Zr0.5(PO4)3 (LSAZP) ceramic electrolyte. The Rietveld refinement of room temperature X-ray diffraction (XRD) data confirms a pure rhombohedral phase (R3‾c) for LSAZP ceramic sintered at 1050 °C. Temperature-dependent synchrotron XRD data demonstrates an increase in lattice parameter c with a positive coefficient of thermal expansion (+2.40 × 10−5 K−1) and a negative coefficient of thermal expansion (−1.26 × 10−6 K−1) for the lattice parameter a with increasing temperature. Interestingly, despite the anisotropic thermal expansion, no intergranular cracks, typically observed in rhombohedral NASICON-type phases, are noticeable in the scanning electron micrographs of the LSAZP samples. The sample sintered at 1050 °C (relative density ∼90 %) exhibits an excellent room temperature conductivity of ∼2.95 × 10−4 S cm−1 and activation energy ∼0.39 ± 0.02 eV. The Li-ion transference number is ∼0.99, suggesting that Li-ion is the dominant charge carrier in the sample. During galvanostatic lithium plating-stripping tests, the symmetric Li|LSAZP|Li cell demonstrates excellent lithium plating-stripping stability over 50 h at a current density of 4 μA cm−2.

Excellent adsorption of toxic Cd (II) ions from water with effective antibacterial activity by novel GO-ZnO-curcumin composite.

A significant health risk arises from the bioaccumulation of harmful Cd (II) in drinking water. Here, we report the unique Cd (II) remediation from drinkingwater by using novel GO-ZnO-curcumin composite. The composites were tailored by varying the ratio of GO-ZnO and curcumin. The composites followed Langmuir adsorption isotherm and pseudo-second-order kinetics. ZnO nano-rods were more effective in Cd (II) than ZnO nano-disks. A maximum adsorption capacity of 4580 ± 40mg/gm was achieved for 21G-B with a removal efficiency of 87.5% at neutral pH under optimized conditions. The removal process was governed by ion exchange and electrostatic attraction, followed bycation exchange capacity (CEC). The lattice parameter increase was detected after adsorption of Cd (II) ions. The regeneration and reusability of the composite was studied. Also, the effect of presence of dyes such as methylene blue on Cd (II) adsorption was noted. The latter had negligible effect on Cd (II) removal efficiency from water. The composite showed high antibacterial activity against B. subtilis and P. aeruginosa with minimum inhibitory concentration (MIC) of 10 ± 0.75µg/ml and 5 ± 1µg/ml respectively due to the presence of zinc. Composite stability was confirmed through leaching and thermal gravimetric analysis (TGA) analysis. The study establishes the nanocomposite as a potential material for remediation of hazardous Cd (II) ions from real water samples under neutral conditions.

Influence of purification methods on the extraction of nanocrystals from bio-hydroxyapatite under consideration of the coalescence phenomenon

The coalescence of nanocrystals that occurs during low-temperature thermal treatments during the purification of hydroxyapatite from pigs has not yet been studied in the context of low-temperature environmentally friendly purification. To preserve the nature of hydroxyapatite, two extraction methods were investigated: Route 1 (autoclave and Soxhlet) and Route 2 (calcination at low temperatures with different times). The focus is on observing the effectiveness of removing fats and proteins while maintaining crystallite size and morphology. DSC showed that coalescence of crystallites occurred at 452, 566, 648, and 704 °C. Raw has a higher IR FWHM (phosphate band) due to the organic material; R1 had a lower FWHM (partial removal of lipids and proteins). Increasing the calcination temperature decreases the FWHM, indicating a shift in vibrational states from surface to bulk, leading to an increase in apparent crystallite size due to coalescence. For 20–80 h at quasi-stable temperatures of 400 and 500 °C, no significant changes occur in the IR spectrum. X-ray diffraction indicates the removal of organic material during calcination, as the peaks become clearer with increasing temperature. The crystallite size is not affected and remains in similar ranges. Purification with hydroxide shows an increase in both lattice parameters, in addition to the fluctuations that occur due to the ionic substitutions that naturally occur in biogenic HAp. And the TEM study confirms that the changes in apparent size from 2D to 3D are the result of the phenomenon of interplanar coalescence at low temperatures that occurs in sintering processes.

Impact of Zn addition on structural, morphological, and magnetic properties of thermally annealed Li–Zn nanoferrite

The effect of Zn addition on cationic distribution, structural and magnetic properties of nanocrystalline Li-Zn ferrites are reported. X-ray diffraction confirms the formation of spinel nanoferrites with an average grain diameter of 34 − 82 nm. The addition of Zn results in a linear increase of lattice parameter and X-ray density. Magnetism in the studied samples is governed by the Yafet-Kittel three-sub-lattice model, shown by a non-zero canting angle. The variation in magnetic properties is correlated with the calculated cationic distribution. A new antistructural modeling explains the changes in the concentration of donor and acceptor surface active centers.

Effect of cobalt doping on the structural, magnetic, optical, and electronic properties of LiFeCr4O8

Cobalt doping's influence on the structural, magnetic, and electronic properties of the double spinel LiFeCr4O8 was systematically investigated. Rietveld refinement revealed a consistent increase in lattice parameter a and unit cell volume with cobalt incorporation. Magnetic susceptibility measurements indicated three distinct transitions: an increase in the ferrimagnetic transition temperature (TN), a decrease in the magnetostructural transition temperature (TMS), and an increase in the spin gap transition by cobalt doping. Through diffuse reflectance spectroscopy the direct optical band gap (Eog) was obtained with values of 1.169 eV, 1.303 eV, 1.396 eV, and 1.230 eV for x = 0.0, 0.1, 0.2, and 0.5, respectively. The observed increase in Eog with cobalt doping suggests a widening of the band gap, which could be beneficial for optoelectronic applications. By means of X-ray photoelectron spectroscopy (XPS) the core levels of Li 1s, Co 3p, Fe 3p, Cr 3p, Fe 2p, Cr 2p, and O 1s were identified. XPS valence band (VB) analysis revealed a decreasing intensity at binding energy BE = 0 eV with respect to x = 0.0. Density functional theory calculations with Hubbard U correction (DFT + U) confirmed a ferrimagnetic semiconductor behavior with a direct electronic band gap (Eeg) of 1.085 eV.

Structure and mechanical properties of TiAlTaN thin films deposited by dcMS, HiPIMS, and hybrid dcMS/HiPIMS

The quaternary Ti1-x-yAlxTayN system exhibits superior thin film properties compared to Ti1-xAlxN. Apart from the Ta content, the sputtering method has a crucial effect on the structural and mechanical properties. High power impulse magnetron sputtering (HiPIMS) produces denser thin films with improved hardness compared to direct current magnetron sputtering (dcMS), but at lower deposition rates. However, a hybrid dcMS/HiPIMS process combines the advantages of dcMS and HiPIMS and is, therefore, a suitable method to synthetize Ti1-x-yAlxTayN thin films. To analyze the effect of the sputtering technique on the structural and mechanical properties, Ti1-x-yAlxTayN is sputtered from TiAlTa compound targets with Ta fractions up to 0.2 by dcMS, HiPIMS, and dcMS/HiPIMS.The Ta metal fraction within Ti1-x-yAlxTayN steadily increased up to y ≈ 0.25, while the Al content notably decreased at higher Ta levels. This reduction was most pronounced in HiPIMS, resulting in an order of decreasing Al content as dcMS, dcMS/HiPIMS, and HiPIMS. All thin films exhibit a Ti1-x-yAlxTayN substitutional solid solution with a linearly increasing lattice parameter corresponding to higher Ta contents. At similar Ta contents, HiPIMS-Ti1-x-yAlxTayN and dcMS/HiPIMS-Ti1-x-yAlxTayN show larger out-of-plane lattice parameters compared to dcMS/HiPIMS-Ti1-x-yAlxTayN, indicating elevated compressive stresses within the thin films. The Ti1-x-yAlxTayN thin films show a column-like structure, with HiPIMS promoting the formation of a denser morphology with less columns. The HiPIMS-Ti1-x-yAlxTayN with H = 41 GPa and dcMS/HiPIMS-Ti1-x-yAlxTayN with H = 40 GPa achieve their peak hardness at a lower Ta metal fraction of y ≈ 0.12–0.13, in contrast to dcMS-Ti1-x-yAlxTayN, which reaches H = 38 GPa at y ≈ 0.25. The shift to lower Ta contents for the maximum hardness in HiPIMS-Ti1-x-yAlxTayN and dcMS/HiPIMS-Ti1-x-yAlxTayN is due to higher compressive stresses and smaller crystallite sizes in these films at low Ta metal fractions. The H/E and H3/E2 ratios of the HiPIMS-Ti1-x-yAlxTayN and dcMS/HiPIMS-Ti1-x-yAlxTayN exhibited a similar trend of increasing values, reaching a maximum, and then decreasing with higher Ta content. Consequently, the hybrid dcMS/HiPIMS process produces Ti1-x-yAlxTayN thin films with mechanical properties comparable to pure HiPIMS, making it a suitable sputtering method for the synthesis of Ti1-x-yAlxTayN.

Influence of cationic vacancy diffusion on the aging behavior of low-temperature SrCo1-xRuxO3 thermosensitive ceramics

The thermosensitive ceramics of negative temperature coefficient (NTC), SrCo1-xRuxO3 (0 ≤ x ≤ 0.8), were synthesized using the solid-phase method. The research systematically explored the phase structure, microstructure, elemental chemical states, electrical properties, and aging performance. X-ray diffraction (XRD) data indicates that with the increase of Ru content, the lattice parameter increases. Scanning electron microscopy (SEM) images reveal a dense and uniform microstructure. X-ray photoelectron spectroscopy (XPS) data indicates the presence of Co2+/Co3+ and Ru4+/Ru5+ ion pairs. Resistive temperature data indicates its potential use as a low-temperature thermosensitive resistance material in the range of 2–300 K. Fitting the resistance-temperature curve using the thermally activated band conduction model and Mott's 3D variable range hopping model. Proposed the Ru–O2--Co hopping model, elucidating the hole hopping transport mechanism in NTC ceramics. Impedance spectroscopy analysis indicates that grain boundary resistance dominates the overall resistance of the sample. After aging at 77 K for 864 h, the maximum aging drift rate of the ceramic material is 1.55 %. Proposed a novel cationic vacancy diffusion model to explain aging phenomena, offering a new perspective for designing high-stability low-temperature NTC thermistors.

Mean-field model for BaFe[formula omitted]Ti[formula omitted]O19 ([formula omitted] 0 and 0.2) hexaferrite: Structural and magnetic properties

An experimental and theoretical investigation of the magnetic properties of Ti-doped barium hexaferrite (BaM) is conducted. Polycrystalline samples of BaFe12−xTixO19 with x≤ 0.2 were synthesized using the solid-state reaction method. X-ray diffraction (XRD) analyses, along with Rietveld refinement, confirmed the presence of BaFe12O19 as the predominant BaM phase and a minor amount of hematite in all samples. Structural analysis revealed a slight increase in lattice parameters a and c for x=0.2. A result mostly related to the preferential occupation of Ti4+ ions at the 4f2 and 12k sites, coupled with the reduction of Fe3＋ ions to Fe2＋. It was also found that the magnetic response of samples is affected by Ti4+ substitution. Saturation magnetization slightly decreased from ∼ 45 (x= 0) to ∼ 44 emu/g (x= 0.2), the anisotropy constant from ∼4.08× 105 to ∼4.06× 105 erg/g2, while coercivity slightly increased from ∼ 2456 to ∼ 2468 Oe, and the anisotropy field from ∼ 18.2 to ∼ 18.6 kOe. The magnetic features of the samples were analyzed in terms of a proposed model based on the mean-field theory. Results indicated that the substitution of Ti4+ ions resulted in a decrease in the magnetic moment of the 2b sublattice. Such behavior is influenced by its closest neighboring sites 12k and 4f2 sublattices, which are the preferred occupancy sites for the Ti4+ cations.

Effect of F− doping on structural, elastic, and electronic properties of SmO1−xFxBiS2: A first principles investigation

Structural, elastic, and electronic properties of SmO1−xFxBiS2 were studied using first principles method, and effects of F− doping were clearly observed. By increasing x, the increase of lattice parameter ‘a’ and decrease of ‘c’ are mainly due to the displacement of S1 and Sm atoms respectively. For x = 0.3, new (Bi–S1)2 bonds formation was observed. The gap between Bi- and S1-planes decreases and disappeared at x = 0.9. Cauchy pressures, B/G, and ν indicate ductile nature having metallic bonds with small ionic contribution. B, G, and E are highly anisotropic and show anomaly at x = 0.3, 0.5, and 0.8. Sm 4f states are mainly responsible for metallicity. For x = 0.3, total DOS decreases due to new bonds formation. Anomalous displacement of Sm-sites by doping at O- or Sm-sites induces anomalous displacement of S1 atoms which may be the main reason for change of different properties of SmO1-xFxBiS2.

Prior implantation of hydrogen as a mechanism to delay helium bubbles, blistering, and exfoliation in titanium

This study explores the delaying of the formation of helium bubbles and blisters in pure titanium by hydrogen pre-implantation. Titanium, implanted with helium (40 KeV, 5 × 1017 ions/cm²), exhibited large bubbles that cause exfoliation after heat treatment, whereas hydrogen pre-implantation inhibited bubble growth at room temperature and reduced the exfoliation after heat treatment.In the samples pre-implanted with hydrogen, we found evidence of helium diffusion delay by: (a) a fourfold reduction in bubble pressure (b) faceted cavities in the samples (c) a smaller increase in titanium lattice parameters (d) a 16-fold reduction in average bubble size and a sixfold reduction in bubble area fraction (e) a more than twofold decrease in exfoliation (f) a tendency toward the formation of larger bubbles as a result of heat treatment. We believe that it is reasonable to assume that the inhibition of helium diffusion between tetrahedral interstitial lattice sites takes place because of the occupation of the intermediate octahedral sites by hydrogen atoms.Evidence for the opposite effect, that is inhibition of the diffusion of hydrogen in the presence of helium, is found in the retention of hydrogen in the specimens at elevated temperatures. This retention allowed the existence of titanium hydride after heat treatment at 680 °C. The present study sheds light on the intricate interplay between hydrogen and helium in titanium, providing insights into mechanisms that can potentially mitigate helium-induced damage in materials.

Effect of particle size and composition on local magnetic hyperthermia of chitosan-Mg1-xCoxFe2O4 nanohybrid.

In this study, Mg1-xCoxFe2O4 (0≤x ≤ 1 with ∆x = 0.1) or MCFO nanoparticles were synthesized using a chemical co-precipitation method and annealed at 200, 400, 600, and 800°C respectively to investigate the structural properties of the materials by X-ray diffractometer (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR). Controlled annealing increased particle size for each value of x. The aim was to investigate how specific loss power (SLP) and maximum temperature (Tmax) during local magnetic hyperthermia were affected by structural alterations associated with particle size and composition. The lattice parameter, X-ray density, ionic radius, hopping length, bond length, cation-cation distance, and cation-anion distance increase with an increase in Co2+ content. Raman and FTIR spectroscopy reveal changes in cation distribution with Co2+ content and particle size. Magnetic properties measured by the physical property measurement system (PPMS) showed saturation magnetization (Ms), coercivity (Hc), remanent magnetization (Mr/Ms), and anisotropy constant (K1) of the Mg1-xCoxFe2O4 nanoparticles increase with Co2+ content and particle size. When exposed to an rf magnetic field, the nanohybrids experienced an increase in both the SLP (specific loss power) and Tmax (maximum temperature) as the particle size initially increased. However, these values reached their peak at critical particle size and subsequently decreased. This occurs since a modest increase in anisotropy, resulting from the presence of Co2+ and larger particle size, facilitates Néel and Brownian relaxation. However, for high anisotropy values and particle size, the Néel and Brownian relaxations are hindered, leading to the emergence of a critical size. The critical size increases as the Co2+ content decreases, but it decreases as the Co2+ content increases, a consequence of higher anisotropy with the increase in Co2+. Additionally, it is noteworthy that the maximum temperature (Tmax) rises as the concentration of nanohybrids grows, but the specific loss power (SLP) decreases. An increased concentration of chitosan-MCFO nanohybrids inhibits both the Néel and Brownian relaxation processes, reducing specific loss power.

Cationic migration effect on the dielectric and magnetic properties of CoFe2O4/ZnO composites

The present paper focusses on the effect of cationic migration in the sintered CoFe2O4/ZnO composite. The increase in lattice parameter of the CoFe2O4 after sintering indicates substitution of Zn. Mӧssbauer analysis of the samples indicates the transformation of composites to paramagnet in the sample sintered at 600 and 750 °C. At 900 °C, a low hyperfine field sextet was evolved complimented by MH loop which is due to redistribution of cations and formation of ferromagnetic phase. Maxwell-Wagner dispersion was identified by the frequency-dependent fluctuation of dielectric constants (ε׳) and dielectric loss (tan δ). Dielectric constant values of 8.66, 7.90, 9.31 and dielectric loss value of 0.11, 0.03, 0.05 were found for CZ6, CZ7 and CZ9 respectively at 1 MHz frequencies. The composite are suitable for high frequency applications due to its low loss, high resistance, low sintering temperature. The mechanisms behind these observations are discussed in this paper.

Effects of structural strain and phase transformations on the mechanical properties of alumina-zirconia-graphene composites

Yttria-stabilized-zirconia (YSZ) plus graphene-based-materials composites may present phase transitions. Consequently, it may affect the composite properties. Thus, this work discusses the causality between lattice strain, phase transition, fracture toughness (Kc) and hardness (H) values in alumina+YSZ matrix reinforced with 0 wt.% up to 1.25 wt.% multilayered-graphene (MLG). The conventional sintering was made in a reducing atmosphere. H and Kc were obtained by Vickers indentation. The structural characterization shows that the MLG addition promoted an increase in YSZ lattice parameters and a phase transition, from tetragonal to cubic. As a result, the optimum reinforcement peak in the H and in the Kc happens in different MLG concentrations. The Kc optimum is in lower MLG amount, explained by microstructural features. On the other hand, the optimum H displaced to higher MLG concentration may be effect of increasing lattice parameters and the cubic-YSZ phase proportion.