Average Lattice Constant Research Articles

Impact of substituting Cu2+/Ce3+ cations on the structural, magnetic and electrical properties of cobalt nano ferrites

The nano ferrite compounds Co1-xCuxFe2-yCeyO4 (with x values of 0.0, 0.25, 0.5, and 0.75, and y values of 0.0, 0.03, 0.06, and 0.09) were synthesized through the sol-gel auto-combustion method. The characteristics of spinel ferrites were tailored by creating nano ferrites with desirable properties, which were then sintered at 1150 °C for 2 h in the presence of rare earth (Ce3+) and transition metals (Cu2+). They were investigated using dielectric, FTIR, FESEM, XRD, VSM, and DC electrical resistivity experiments. XRD examination verified the samples' cubic spinel structure by measuring the average crystallite size, x-ray density, and lattice constant. FESEM images revealed grain sizes ranging from 41.07 to 156 nm. FTIR spectra in the range of 415 cm−1 to 430 cm−1 further supported the substitution of Cu2+/Ce3+ ions in the tetrahedral sites, indicated by an increase in the lattice parameter. Measurements of the remanence ratio, saturation magnetization, anisotropy constant, coercivity, and magnetic moment, among other magnetic characteristics, were made. Higher concentrations of Cu2+/Ce3+ ions were found to considerably reduce magnetic saturation (Ms), coercivity (Hc), and remanence (Mr). These materials were semiconducting because their activation energy varied between 0.52 and 0.62 eV, and their DC resistivity increased with increasing Cu2+/Ce3+ concentration. Above 1 MHz, the dielectric properties became frequency-independent and decreased with increasing frequency. These ferrites seem highly potential for devices working at high frequency.

Structural and optical properties of green-synthesised tricobalt tetroxide nanoparticles

In this study, we investigated the structural and optical properties of garlic extract-based green-synthesised tricobalt tetroxide nanoparticles. Transmission electron microscopy revealed a particle size range of 8–22 nm for the prepared powder sample. Powder x-ray diffraction data and Rietveld refinement results confirmed the spinel cubic crystal structure of the tricobalt tetroxide nanoparticles, with an average crystallite size of 11.23 nm. This crystal structure corresponds to the Fd3̅m space group and has an average lattice constant of 0.791 nm. The bond lengths of Co3+–O2− and Co2+–O2− are measured to be 0.188 nm and 0.190 nm, respectively. The FTIR data provided evidence of the presence of various functional bands, which helped qualitatively determine the purity of the sample. The UV–vis spectrum estimated two direct energy band gap values (3.7 eV and 2.2 eV) that may be useful for efficient interaction with a wide range of ray spectra to create more electron–hole pairs for various photo-responsive applications, such as dye degradation, solar cells, and optoelectronic components.

Influence of Post-Annealing Treatment on Some Physical Properties of Cerium Oxide Thin Films Prepared by the Sol–Gel Method

In this study, thin films of Cerium Oxide CeO2 were fabricated using the sol–gel technique and deposited onto a glass substrate. The annealing process was carried out at various temperatures ranging from 200 to 600 °C to investigate the structural, morphological, and optical properties of the films and their interrelations. X-ray diffraction (XRD) patterns revealed the crystalline nature of the prepared films, with film quality exhibiting enhancement with increasing annealing temperature. The average crystallite size, dislocation density, microstrain, and lattice constant were determined from XRD patterns. Higher annealing temperatures were found to increase the crystallite size values from 4.71 to 15.33 nm and decrease the dislocation density and microstrain of the unit cell. Scanning electron microscope (SEM) images illustrated the uniformity of the films, presenting a spheroid shape. Optical properties such as transmittance, absorbance, reflectance, the direct band gap, extinction coefficients, the refractive index, and optical conductivity were assessed using optical measurements. The direct optical band gap of the CeO2 film was observed to decrease from 3.99 to 3.75 eV with increasing film thickness. Using the Wemple and DiDomenico (WDD) single-oscillator model, dispersion energy parameters were calculated based on the refractive index. The nonlinear optical properties of the CeO2 thin films were evaluated using these dispersion energy parameters. The improvement of optical parameters holds significance in standardizing CeO2 thin films for various optoelectronic applications.

Bi1.8Gd0.1Er0.05M0.05O3 (M = Pr, Sm, Dy and Y) electrolytes for intermediate temperature solid oxide fuel cells

In this study, a novel solid electrolyte system consisting of co-doped cubic phase stabilised bismuth oxide was successfully synthesized via the sol-gel method. X-ray diffraction (XRD) analysis revealed that all synthesized samples exhibited stable cubic fluorite-type structures. Notably, as the dopant ion radius decreased, a trend of increasing full width half maximum (FWHM) of the main (111) peak and crystal microstrain, along with a decrease in the average crystallite size and lattice constant, was observed. Interestingly, the sample Bi1.8Gd0.1Er0.05Pr0.05O3, possessing a dopant ion radius closest to Bi3+ (1.17 Å), exhibited exceptional electrical properties, achieving a high conductivity of 0.347 S cm−1 at 800 °C and a low activation energy of 0.20 eV for the high-temperature regions (HTR). This superior performance was attributed to the significant role played by the grain boundary volume and conductivity in facilitating ionic conduction, thus explaining the variations in conductivity among the different samples.

Investigating the Antibacterial and Anti-inflammatory Potential of Polyol-Synthesized Silver Nanoparticles.

Silver nanoparticles (Ag-NPs) were synthesized by using the polyol method. The structural and morphological characteristics of Ag-NPs were studied by using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). The XRD analysis revealed the formation of single-phase polycrystalline Ag-NPs with an average crystallite size and lattice constant of ∼23 nm and 4.07 Å, respectively, while the FE-SEM shows the formation of a uniform and spherical morphology. Energy-dispersive X-ray spectroscopy confirmed the formation of single-phase Ag-NPs, and no extra elements were detected. A strong absorption peak at ∼427 nm was observed in the UV-vis spectrum, which reflects the surface plasmon resonance (SPR) behavior characteristic of Ag-NPs with a spherical morphology. Fourier-transform infrared (FTIR) spectra also supported the XRD and EDX results with regard to the purity of the prepared Ag-NPs. Anti-inflammatory activity was tested using HRBCs membrane stabilization and heat-induced hemolysis assays. The antibacterial activity of Ag-NPs was evaluated against four different types of pathogenic bacteria by using the disc diffusion method (DDM). The Gram-negative bacterial strains used in this study are Escherichia coli (E. coli), Klebsiella, Shigella, and Salmonella. The analysis suggested that the antibacterial activities of Ag-NPs have an influential role in inhibiting the growth of the tested Gram-negative bacteria, and thus Ag-NPs can find a potential application in the pharmaceutical industry.

Solute-strengthening in metal alloys with short-range order

Recent surging interest in strengthening of High Entropy Alloys (HEAs) with possible chemical ordering motivates the development of new theory. Here, an existing theory for random alloys that accounts for solute-dislocation and solute–solute interactions is extended to include strengthening due to short-range order (SRO). Closed form expressions are presented for the yield strength and energy barrier of dislocation motion in alloys with SRO based on inputs of atomic misfit volumes, average lattice and elastic constants, the SRO parameters, and effective pair interactions between solutes. The theory shows both the long-established athermal strengthening effect of SRO as well as a notable effect of SRO on the misfit volume strengthening, which can increase or decrease strength. The generalized solute-strengthening theory is the most comprehensive to date that is applicable to macroscopically homogeneous single-phase alloys using inputs that can be measured, computed, or estimated.

Enhanced Structural and Electrochemical Properties of Zn-Doped NiCo2O4 Synthesized by Low-Temperature Microwave Hydrothermal Process

The specific capacitance (Cp) is an important parameter influencing the energy storage capacity of materials. In this study, a series of NiZn x Co2-x O4 (x = 0.0–0.10) nanoparticles were prepared using the microwave-hydrothermal (M-H) method. The samples were characterized by using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform Infrared (FTIR), X-ray photoelectron spectroscopy (XPS) and electrochemical studies. It is observed from X-ray diffraction that all the samples are cubic in nature with space group Fd-3m. The average lattice constant is varied in between 7.63 (x = 0.0) to 8.34 (x = 0.10). The linear increase in lattice constant is due to the difference in the ionic radii. The average grain size is in the range of 80 (x = 0.0) − 124 nm (x = 0.10) for all the samples, and grains are found to be spherical in nature. The characteristic metal oxygen vibration bands were observed at 578 cm−1 and 661 cm−1. The valence states of Ni2+/Ni3+, Co2+/Co3+ and Zn2+ were confirmed by X-ray photoelectron spectroscopy. The electrochemical studies were performed on all the samples. The high value of specific capacitance (Cp) 871.91 Fg−1 is observed for sample x = 0.06. Therefore, Zn doped NiCo2O4 shows good impedance and electrochemical properties which is promising material for supercapacitor applications.

Structural, magnetic, dielectric and spectroscopic impedance analysis of magnesium iron oxide thin films synthesized by electrodeposition: Effect of preferred orientation

Magnesium iron oxide is the most valuable and versatile spinel system with reduced eddy current and dielectric losses. Spinel ferrites are electrically non-conductive. The electrodeposition is used to synthesize thin films on Cu substrate. A set of five thin films is prepared by varying the in-situ oxidation time (10 min, 15 min, 20 min, 25 min and 30 min) and a fixed deposition time of 25 min. The x-ray diffractometer XRD (phase confirmation), Scanning Electron Microscope SEM (morphological analysis), Fourier transforms infra-red spectroscope FT-IR (bond-formation), impedance analyzer (dielectric-measurements) and vibratory sample magnetometer VSM (magnetic properties) has been utilized to examine the prepared samples. All the studied samples have been found, single-phase spinel structures. XRD shows the pure phase formation of spinel MgFe2O4 at 20 min, 25 min, and 30 min. The exchange of the preferred orientation (PO) from (731) mixed phase to (533) spinel is observed. This change in preferred orientation has been caused the changes in the properties of prepared thin films. The average lattice constant, cell volume, x-ray density and crystallite size of magnesium-iron oxide were found at 8.3814 Å, 588.58 (Å)3, 3.2098 g/cm3 and 24.0392 nm respectively. In FTIR analysis of magnesium-iron oxide, two characteristic spinel bands are observed below 700 cm−1. The SEM result showed a smooth granular structure at 30 min. The normal behavior of the dielectric constant and single semicircle is observed in cole-cole plot. All the prepared thin films are ferromagnetic in nature. At 30 min, a higher dielectric constant, 20.2 (log f = 5) and 162.3 emu/cm3 saturation magnetization. The remarkable dielectric and magnetic findings are promising for using electrodeposited thin films in electronic and spintronic devices.

Optical behavior and electrical conductivity of ferromagnetic nanostructured Co:Fe thin films

Recently, there has been an increasing interest in optical applications of nanostructured metal thin films based on transparent conductive layers. There is little data published on the study of the optical behavior of ferromagnetic materials such as Co:Fe alloy thin films. DC sputtering technique was used to grow the magnetic crystalline Co:Fe thin films, on glass substrates, in different nano-thicknesses in range of 20, 35, 50, 75 and 100[Formula: see text]nm. XRD technique, atomic force microscopy (AFM), and a spectrophotometer of Ultraviolet–visible (UV–Vis) were used to analyze the films. The XRD data confirmed that the samples of Co:Fe films showed out-of-plane direction of [Formula: see text]. The data indicates that an increase in the average grain size and lattice constant of the films is presented related to increase in the nano-thickness of Co:Fe alloy thin films samples. From AFM, it is illustrated that the roughness of the film is about ([Formula: see text][Formula: see text]nm) which is due to the produced grains. The optical response, optical conductivity and electrical conductivity have been affected by the changed nano-thickness of the metallic Co:Fe thin films.

Studies of the microstructural, magnetic, electrical, and dielectric properties of Mg0.6T0.4Cr2O4 (T = Ni, Cu) spinel chromites for magnetic, high frequency, and microwave applications

In this study, the structural, morphological, magnetic, electrical, and dielectric properties of Mg0.6T0.4Cr2O4 (T = Ni, Cu) spinel chromites were studied. The X-ray diffraction data reveal that the average crystallite size, lattice constant, and X-ray density increase with the substitution of Ni by Cu. The average crystallite size value rises from 58 nm (for Mg0.6Ni0.4Cr2O4) to 73 nm (for Mg0.6Cu0.4Cr2O4). However, saturation magnetization (Ms) decreases from 0.061 emu/g for Mg0.6Ni0.4Cr2O4 to 0.058 emu/g for Mg0.6Cu0.4Cr2O4. The decline in Ms is due to the lower magnetic moment of Cu2+ ions compared to that of Ni2+ ions. Low Hc coercive fields were obtained (53 Oe and 40 Oe for Mg0.6Ni0.4Cr2O4 and Mg0.6Cu0.4Cr2O4, respectively), indicating that the synthesized samples are suitable for use in soft magnetic devices. Temperature and frequency-dependent impedance spectroscopy measurements have been used to study the samples' electrical properties. The NSPT and CBH models were used to explain the samples' conduction process. Due to the increase in crystallite size, the activation energy (Ea) is lower for Mg0.6Cu0.4Cr2O4 (0.136 eV) than Mg0.6Ni0.4Cr2O4 (0.250 eV). The sample impedance properties were interpreted by modeling Nyquist diagrams considering grain and grain boundary contributions. Dielectric-relaxation phenomenon is observed from sample impedance curves. Mg0.6Ni0.4Cr2O4 conductivity data collapse into a single master curve, as predicted by the Ghosh scaling model. However, for Mg0.6Cu0.4Cr2O4, the Summerfield scaling model is more appropriate. Furthermore, the synthesized materials demonstrate high electrical resistivity, as well as low dielectric constants and losses at higher frequencies, making them appropriate for use in microwave absorption devices and high-frequency applications.

Properties of co‐precipitated jack bean starch‐based magnetic nanoparticles derivatives

AbstractLow‐ and high‐derivatives of magnetic starch nanoparticles (MSNPs) are obtained at respective 5 and 10 mL of 25% glutaraldehyde at 60, 70, and 80°C via coprecipitation of iron (II, III) oxide with jack bean starch. Their swelling power, solubility, bulk density, Fourier transform infra‐red (FTIR) patterns, thermogravimetric analysis (TGA)‐differential thermal analysis (DTA), x‐ray diffraction (XRD), Brunauer–Emmet–Teller (BET) properties, and morphology are analyzed. The results show that the MSNPs derivatives are pH‐responsive and temperature‐dependent. Peak swelling power (4.19 ± 0.01 g/g) of MSNPs derivative is obtained at 60°C. MSNPs derivatives are more soluble in acidic medium than alkaline medium. Bulk density improves three times more in MSNPs derivatives. FeO stretching bonds are observed at 530.73, 551.03, and 621.44 cm−1 for the MSNPs derivatives in addition to peaks of OH stretching at 3251.06 cm−1 (native starch [NS]), 3308.41 cm−1 (low‐substituted MSNPs), and 3133.28 cm−1 (high‐substituted MSNPs). The TGA‐DTA curves are endothermic and MSNPs are thermally stable beyond 700°C. MSNPs derivatives exhibit average lattice constant of 0.82382 nm with prominent peaks at 30.00° 2θ and 32.00° 2θ. MSNPs derivatives are mesoporous with peak BET surface area of 50.462 m2g−1. The microstructures of NS and MSNPs derivatives are predominantly oval. The MSNPs studied can serve as alternative functional biomaterials and nanosorbents.

Mössbauer and Structure-Magnetic Properties Analysis of AyB1-yCxFe2-xO4 (C=Ho,Gd,Al) Ferrite Nanoparticles Optimized by Doping.

AyB1-yCxFe2-xO4 (C=Ho,Gd,Al) ferrite powders have been synthesized by the sol-gel combustion route. The X-ray diffraction of the CoHoxFe2-xO4 (x = 0~0.08) results indicated the compositions of single-phase cubic ferrites. The saturation magnetisation of CoHoxFe2-xO4 decreased by the Ho3+ ions, and the coercivity increased initially and then decreased with the increase of the calcination temperature. The Mössbauer spectra indicated that CoHoxFe2-xO4 displays a ferrimagnetic behaviour with two normal split Zeeman sextets. The magnetic hyperfine field tends to decrease by Ho3+ substitution owing to the decrease of the A-B super-exchange by the paramagnetic rare earth Ho3+ ions. The value of the quadrupole shift was very small in the CoHoxFe2-xO4 specimens, indicating that the symmetry of the electric field around the nucleus is good in the cobalt ferrites. The absorption area of the Mössbauer spectra changed with increasing Ho3+ substitution, indicating that the substitution influences the fraction of iron ions at tetrahedral A and octahedral B sites. The X-ray diffraction of Mg0.5Zn0.5CxFe2-xO4(C=Gd,Al) results confirmed the compositions of single-phase cubic ferrites. The variation of the average crystalline size and lattice constant are related to the doping of gadolinium ions and aluminum ions. With increasing gadolinium ions and aluminum ions, the coercivity increased and the saturation magnetization underwent a significant change. The saturation magnetization of AlMg0.5Zn0.5FeO4 ferrite reached a minimum value (MS= 1.94 mu/g). The sample exhibited ferrimagnetic and paramagnetic character with the replacement with Gd3+ ions, that sample exhibited paramagnetic character with the replacement with Al3+ ions, and the isomer shift values indicated that iron is in the form of Fe3+ ions.

Structural, optical, morphological and magnetic properties of Cu0.25M0.75Fe2O4 (M=Mn, Mg, Ni and co) ferrites for optoelectronic applications

The nanostructured Cu0.25M0.75Fe2O4 (M = Mn, Mg, Ni, Co) ferrites were obtained by the sol-gel auto-combustion method and their structural, magnetic, morphological and optical properties were investigated. The characterization techniques like XRD, UV–Vis, VSM, SEM, EDX and FTIR were employed to explore the obtained spinel ferrites. The XRD analysis revealed that all the compounds were single-phased spinels, showing no secondary phase peaks in the diffraction patterns. According to Vegard's law, the average lattice constant of ferrites calculated from XRD data ranged from 8.413 Å to 8.131 Å, whereas crystallite sizes ranged from 18.978 nm to 42.351 nm on account of the increased annealing temperatures. The SEM study revealed that the ferrites powder morphology consisted of a merger of spherical and octahedral-shaped grains. The EDX study confirmed the stoichiometric ratios of constituent contents of Cu0.25M0.75Fe2O4 (M = Mn, Mg, Ni, Co) ferrites. In the M-doped Cu0.25M0.75Fe2O4 (M = Mn, Mg, Ni, Co) ferrites, the Jahn-Teller effect was also raised, as explored by the FTIR study of the ferrites. The UV–Vis spectroscopy analysis showed that the ferrites exhibited a direct band gap ranging from 2.961 eV to 2.189 eV. The M − H hysteresis curves of the ferrites recorded by VSM at room temperature revealed that the saturation magnetization, retentivity, coercivity, squareness, magnetic anisotropy and the magnetic moment severely depended on the substituent M content of ferrites. The investigation of magnetic properties also indicated that the successive substitutions of M in Cu0.25M0.75Fe2O4 (M = Mn, Mg, Ni, Co) ferrites changed its behavior from ferrimagnetic to ferromagnetic, even though the Jahn-Teller effect significantly interrupted such a transition. This feature enabled a practical application of Cu0.25M0.75Fe2O4 (M = Mn, Mg, Ni, Co) ferrites in optoelectronic devices.

Effect of metal ions on structural, morphological and optical properties of nano-crystallite spinel cobalt-aluminate (CoAl2O4)

The bright blue nano crystallite cobalt aluminate (CoAl2O4) was synthesized by sol–gel method using a mixture of chelating agent of glycerol and citric acid. The effects of changing (0.05, 0.075, 0.10, 0.25, 0.50, and 0.75 mol/L) metal ion concentration on the structural, morphological and color properties of synthesized CoAl2O4 were characterized by using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), Nanoparticle size analyzer, Simultaneous Thermal Analyzer (STA), UV–vis absorption spectroscopy, and CIE-LAB colorimetric analysis. From the X-ray peak profile analysis, the crystallite size was measured by Debye-Scherrer (D-S) equation, and three different models presenting average crystallite sizes between 88.3 and 125.4 nm.The average lattice strain, dislocation density, lattice constant, cell volume, and zeta potential were between 0.00021 and 0.0058, (1.73 to 12.8) × 1014 (lines/m2), 8.10658 to 8.11181 Å, 533.60 to 533.81 Å3, −56.4 to − 63.5 mV, respectively. Using UV–vis absorption spectroscopy, the band gap was calculated from Kubelka-Munk method, and the values of band gap increasing from 1.82 to 1.84 eV, respectively. The reflectance spectra and the CIE-L*a*b* values of cobalt aluminate is also measured which confirmed the formation of blue nano crystallite cobalt aluminate.

Novel copper-sawdust nanocomposite preparation and evaluation

A readily available and reasonably priced lignocellulosic material that comes from nature is sawdust or wood shaving. It is a waste product of both industry and agriculture that is widely distributed and has disposal issues. The management of waste (such as sawdust) and research into transforming it into various compounds for specialized purposes and objectives have recently drawn a lot of interest. Therefore, the primary objective of this investigation can be summed up as showcasing sawdust as a type of intriguing bio-waste and turning it into wealth for a variety of applications. Copper-Sawdust nanocomposites have been produced into powder and rectangular slabs using the chemical reduction method.The nanocomposite was investigated with Transmission Electron Microscopy which revealed a spherical shape with particle sizes ranging between 3 and 14 nm. Electron diffraction studies confirmed the planes (111), (200), and (220) as well as the presence of metal copper.X-ray Diffraction studies confirmed the Miller indices for the characteristic high-intensity peaks in the range 35°- 65° as (111), (200), and (220) with corresponding Crystallite sizes as 14.4 nm, 14.7 nm, and 11.9 nm respectively. The crystallite size was comparable to the actual size of the Nanocomposite confirming the precision of the results. The average lattice constant is 4.23Å. The research also confirms that the copper nanoparticle was crystalline with Face Centered Cubic (FCC) structure similar to the bulk Copper. The Electron diffraction and the X-ray diffraction also confirmed similar planes. The current study indicates that Copper nanocomposite may find use in several industrial domains making it extremely beneficial to the scientific community.

Enhancement in structural, morphological, and optical properties of copper oxide for optoelectronic device applications

AbstractIn this study, copper oxide (CuO) specimens were successfully prepared by the hydrothermal process at altered calcination temperatures; 350, 450, and 550°C. The synthesized samples were analyzed through X-ray powder diffraction (XRD), scanning electron microscope (SEM), Raman, Fourier-transform infrared spectroscopy (FTIR), and UV-Vis spectroscopy to analyze the impact of calcination temperature on the structural, morphological, vibration spectra, functional group, and optical properties of CuO for optoelectronic device applications. XRD confirms the pure single-phase monoclinic structure of synthesized samples with no impurity phases and has good crystallinity with the development in calcination temperature. The average crystalline size, lattice constant, and porosity were found in the range of 3.98–5.06 nm;a= 3.4357 Å,b= 3.9902 Å,c= 4.8977 Å – a= 3.0573 Å,b= 3.9573 Å,c= 4.6892 Å; and 3.37–1.03%, respectively. SEM exhibited a variation in morphology by increasing calcination temperature. Raman spectra revealed that the CuO sample calcinated at 550°C with a stone-like shape having a large grain size of 3.25 μm exhibited that Raman peak intensity and the multiphonon band became stronger and sharper and exhibited higher intensity compared to the samples calcinated at 350 and 450°C. FTIR spectra confirmed that these synthesized specimens exhibited the peaks associated with the typical stretching vibrations of the Cu–O bond between 400 and 500 cm−1exhibiting the formation of CuO. The energy bandgap was slightly reduced from 1.61 to 1.43 eV with the increase in the calcination temperature. The optical studies revealed that the calcination temperature of 550°C improves the optical properties of CuO by tuning its optical bandgap. The modified structural, morphological, and optical characteristics of the prepared CuO samples make them an appropriate candidate for optoelectronic device applications.

Investigating the Impact of Cu2+ Doping on the Morphological, Structural, Optical, and Electrical Properties of CoFe2O4 Nanoparticles for Use in Electrical Devices.

This study investigated the production of Cu2+-doped CoFe2O4 nanoparticles (CFO NPs) using a facile sol−gel technique. The impact of Cu2+ doping on the lattice parameters, morphology, optical properties, and electrical properties of CFO NPs was investigated for applications in electrical devices. The XRD analysis revealed the formation of spinel-phased crystalline structures of the specimens with no impurity phases. The average grain size, lattice constant, cell volume, and porosity were measured in the range of 4.55–7.07 nm, 8.1770–8.1097 Å, 546.7414–533.3525 Å3, and 8.77–6.93%, respectively. The SEM analysis revealed a change in morphology of the specimens with a rise in Cu2+ content. The particles started gaining a defined shape and size with a rise in Cu2+ doping. The Cu0.12Co0.88Fe2O4 NPs revealed clear grain boundaries with the least agglomeration. The energy band gap declined from 3.98 eV to 3.21 eV with a shift in Cu2+ concentration from 0.4 to 0.12. The electrical studies showed that doping a trace amount of Cu2+ improved the electrical properties of the CFO NPs without producing any structural distortions. The conductivity of the Cu2+-doped CFO NPs increased from 6.66 × 10−10 to 5.26 × 10−6 ℧ cm−1 with a rise in Cu2+ concentration. The improved structural and electrical characteristics of the prepared Cu2+-doped CFO NPs made them a suitable candidate for electrical devices, diodes, and sensor technology applications.

Revealing the dimensional stability mechanisms of SiC/Al composite under long-term thermal cycling

Long-term thermal cycling causes irreversible dimensional changes of the material, which in turn affects the reliability of precision instruments. In this paper, dimensional stability mechanisms of SiC/Al composites during thermal cycling were revealed using high-precision thermal dilatometer, XRD and spherical aberration correction transmission electron microscope (Cs-TEM). First, how the factors including dislocations, internal stress and precipitates affect the dimensional change of SiC/Al composites were separately introduced. Then, the integrated effect of these factors affecting the dimensional stability of SiC/Al composites was further discussed. Among them, the integrated effect of dislocation-internal stress in SiC/pure Al composites leads to an increase in dislocation density and average lattice constant, which leads to an increase in dimensional change. The integrated effect of dislocation-internal stress-precipitates in SiC/2024Al composites leads to a decrease in the average lattice constant and some changes in the precipitation behavior (including the type, density and lattice constant of the precipitates), which ultimately leads to a decrease in dimensional change. The dimensional change of the two types of composites was semi-quantitatively estimated. Finally, the reasons for the significantly higher dimensional stability of the SiC/2024Al composites were given.

Hyperbolic-tangent composition-graded InxGa1-xAs/GaAs (100) structures grown by molecular beam epitaxy

The molecular beam epitaxial growth and physical properties of In graded-composition layers of InGaAs on GaAs (100) substrates varying nominal In concentration from 12 to 97% and vice versa is analyzed along the growth front. The substrate temperature was varied as the In concentration was changed in order to propitiate the near-optimal growth conditions for the InGaAs alloy. Hyperbolic-tangent compositional gradients, from In-rich to Ga-rich alloys and vice versa, observed RHEED patterns characteristic of a flat surface during the growth. The HRXRD patterns showed clear diffraction peaks associated with the In concentration alloy at which the graded sample started, followed by a characteristic plateau of graded layers. The occurrence of dislocations in hyperbolic tangent gradients that relieve the strain up to a certain thickness is explored, reaching a nominal or an averaged lattice constant.

Investigation of the characteristics of the InGaAs/InAlGaAs superlattice for 1300 nm range vertical-cavity surface-emitting lasers

X-ray structural analysis and photoluminescence spectroscopy techniques were used to study heterostructures based on InGaAs/InAlGaAs superlattice for active regions of 1300 nm range lasers grown by molecular beam epitaxy. It is shown that the grown heterostructures have a high crystal quality. The perpendicular lattice mismatch of the average crystal lattice constant of the InGaAs/InAlGaAs superlattice with respect to the crystal lattice constant of the InP substrate is estimated at ~+0.01%. An analysis of the photoluminescence spectra made it possible to conclude that the contribution of Auger recombination is insignificant in the studied range of excitation power density. Studies of vertical-cavity surface-emitting lasers with an active region based on the InGaAs/InAlGaAs superlattice made it possible to estimate the gain coefficient at a level of 650 cm-1 for the standard logarithmic approximation of the dependence of the gain on the current density. The transparency current density of the laser was 400-630 A/cm2, which is comparable to the record low values for the case of highly strained InGaAs-GaAs and InGaAsN-GaAs quantum wells in the spectral ranges of 1300 nm, respectively. Keywords: superlattice, vertical-cavity surface-emitting laser, optical gain.