Effect Of Ga Substitution Research Articles

Effect of Ga substitution on grain orientation and magnetostrictive properties of polycrystalline CoFe2O4 ceramics prepared by the solid-state method

As a kind of magnetostrictive ceramics, cobalt ferrites are widely concerned because of its large magnetostriction and high resistivity, which are ideal for high-frequency applications. But, the high driving magnetic field due to the high magnetocrystalline anisotropy limits the practical applications of cobalt ferrites, thus, it is a still a challenge to find a balance between high magnetostriction properties and low driving magnetic fields. In this work, we investigated the effects of partially substitution of Ga3+ for Fe3+ on grain orientation and magnetic properties, attempting to maintain high magnetostriction while reducing the driving magnetic field. The CoFe2-xGaxO4 (x=0, 0.05, 0.1, 0.15) with single-phase spinel structure were prepared by the conventional solid-state method. The saturation magnetization MS increased with the increase of Ga concentration, meanwhile the coercivity Hc and magnetocrystalline anisotropy constant K1 significantly decreased, which indicates the better soft magnetic characteristics of the Ga-doped cobalt ferrites. The oriented CoFe2-xGaxO4 samples were obtained using magnetic field orientation technique during the powder forming process. The <001> preferred orientation was achieved in CoFe2O4 samples. However, the <001> orientation degree decreased with the substitution of Ga, and the preferred orientation has changed into <111> at x=0.15. The Ga substitution affected the magnetocrystalline anisotropy and grain orientation, thereby affecting the magnetostrictive properties. As for the non-oriented samples, although the maximum magnetostrictive strain slightly decreased with Ga substitution, while there was a significant drop in the magnetostrictive saturation field. However, the magnetostriction of the oriented samples decreased significantly with the substitution of Ga due to the change of grain orientation from <001> to <111>.

Optical, Dielectric, Magnetic, Photocatalytic, and Antibacterial Properties of Ga-Doped BiGaxFe1-xO3 Synthesized by the Microemulsion Approach.

The effect of Ga-substitution on bismuth ferrite BiGaxFe1-xO3 (x = 0, 0.05, 0.10, 0.15, 0.20, and 0.25) properties was investigated, which was fabricated using a microemulsion route. X-ray diffraction analysis confirmed that specimens had a single-phase rhombohedral structure with space group R3̅c. The concentration of Ga had an impact on various properties such as structural parameters, crystalline size, porosity, and unit cell volume. The samples exhibited notable values for the dielectric constant, tangent loss, and dielectric loss in the low-frequency range, which declined as the frequency increased due to different polarizations. The increment in the AC conductivity was associated with rise in frequency. The P-E loops demonstrated that the samples became more resistive as the Ga concentration increased. The retentivity (Mr) and saturation magnetization (Ms) values reduced as the Ga content increased, although all samples had Hc values within the range for electromagnetic materials. The Ga-substitution had a synergistic effect on the electrochemical characteristics of BiGaxFe1-xO3, resulting in greater conductivity than that of undoped BiFeO3. These enhanced properties contributed to their higher photocatalytic activity in the degradation of crystal violet under visible light irradiation. The doped BiGaxFe1-xO3 exhibited 79% dye degradation after 90 min of illumination compared to 54% for pure BiFeO3. Recycling experiments confirmed the stability and reusability of the synthesized nanoparticles. The antibacterial activity of the samples was certified against various microbes, and the doped BiGaxFe1-xO3 showed promising activity. Thus, doped materials are good candidates for memories, dielectric resonators, and photovoltaics because of their high dielectric constant and AC conductivity, while their higher photocatalytic activity under visible light makes them promising photocatalysts for removing noxious and harmful effluents from wastewaters.

Effect of Ga substitution with Al in ZSM-5 zeolite in methanethiol-to-hydrocarbon conversion.

The catalytic properties of conventional H-[Al]-ZSM-5 and gallium-substituted H-[Ga]-ZSM-5 were evaluated in the conversion of methanethiol to ethylene (CH3SH → 1/2C2H4 + H2S). Dimethyl sulfide (DMS), aromatics, and CH4 were formed as byproducts on the H-[Al]-ZSM-5 catalyst. The introduction of Ga into the ZSM-5 structure provided a high ethylene yield with relatively high selectivity for olefins. Based on the temperature-programmed desorption of NH3 and pyridine adsorption on zeolites, the strength of acid sites was decreased by introducing Ga into the ZSM-5 structure. Undesirable reactions seemed less likely to occur at weakly acidic sites. The suppression of the formation of dimethyl sulfide (CH3SH → 1/2C2H6S + 1/2H2S) and the sequential reaction of ethylene to produce aromatics provided a high yield of ethylene over H-[Ga]-ZSM-5.

Effects of Ga Substitution on the Local Structure of Na2Zn2TeO6.

In the work presented here, we prepared Ga-substituted NZTO (Na2–xZn2–xGaxTeO6, x = 0.00, 0.05, 0.10, 0.15, 0.20) layered materials with a soft chemical, citric acid-based synthesis method and characterized these by means of X-ray diffraction (XRD), 23Na and 125Te NMR, and by density functional theory (DFT) modeling. The influence of randomly distributed Ga cations on the 125Te NMR spectra confirms the successful synthesis. With DFT-based linear response computations, we show that the local distribution of Na ions in the two neighboring interlayers influences the 125Te chemical shift, consistent with observations. DFT modeling suggests that some of the Na sites are rarely occupied in pure NZTO but become favorable upon Ga substitution. There are clear indications that Ga substitution gives an uneven distribution of Na ions in neighboring interlayers and that the Na structure in one layer affects the adjacent layers.

Effects of Ga Substitution on Micromorphology and Static Magnetic Properties of Self-Biased M-Type Sr Hexaferrites

The Sr hexaferrites with chemical formula Sr0.4La0.3Ca0.3Fe11.85-xGaxCo0.15O19 (x = 0.0 — 1.4) were manufactured by traditional ceramic method. The affect of Ga substitution on static magnetic properties and micromorphology of M-type Sr (SrM) hexaferrites have been presented in detail. In accordance with the experiment results, as Ga-substituted content x rises up from 0.0 to 1.4, all SrM hexaferrite samples are magnetoplumbite hexagonal structure. The difference between radius of Fe3+ and Ga3+ ions leads to the decrease of lattice constants. As the amount of Ga substitution x increases from 0.0 to 1.4, the 4πMs and 4πMr presents a trend of increasing, but the Hc shows the opposite trend. K1 and Ha of all samples are higher than 2.5×105 J/m3 and 21 kOe respectively, which manifests all samples possess the strong uniaxial anisotropy. The materials discussed in this paper possess huge potential in the application of high frequency self-biased microwave devices.

Effect of Ga substitution on structural and magnetic properties of Fe50Mn25Al25-xGax Heusler alloys

Heusler alloys possess the structure of an ordered compound while displaying most of the properties of metals. Numerous magnetic exchange mechanisms may be operating in such systems. Herein, the structural and magnetic properties have been investigated as a function of substitution of Al by Ga in Fe50Mn25Al25-xGax (x = 0, 2.5, 5.0, 7.5, 10.0) quaternary (pseudo-ternary) full Heusler alloys. The X-ray diffraction analysis confirms the substituting Al by Ga promoting the lattice expansion in the L21 crystal structure in Fe50Mn25Al25-xGax alloys. The line scanning profile using energy dispersive X-ray analysis investigations suggests the homogeneous distribution of Ga in all the alloys. The magnetic moment of the alloys was found to be affected by Ga as the antiferromagnetic counterpart increases with Ga. A decrease in the value of Curie temperature was found with increase in Ga content. A second-order magnetic phase transition was observed in the alloys above room temperature.

Formation of Tl-1212 phase in Ga-substituted Tl(BaSr)Ca1−xGaxCu2O7 superconductor

The effect of Ga substitution on the superconductivity of Tl(BaSr)Ca1-xGaxCu2O7 (x = 0–0.5) is reported. The samples were prepared by solid-state reaction method. XRD patterns showed a single Tl-1212 phase for the x = 0 and 0.1 samples. Unreacted Ga2O3 and other impurity phases were observed in the higher substituted (x = 0.2 to 0.5) samples. The temperature-dependent resistance measurements showed metallic normal state behavior for all samples with onset transition temperature Tc-onset between 94 and 66 K and zero transition temperature Tc-zero between 86 and 55 K. AC susceptibility measurement showed the highest superconducting transition (95 K) and peak temperature (89 K) for non-substituted sample. The intergranular critical current density Jc at Tp for all samples was between 16 and 22 A cm−2. This work showed that the intergranular coupling and flux pinning energy were suppressed with Ga substitution. Some Ga+2 were most likely incorporated at Ca+2 for x = 0.1 and some resided at the grains for x ≥ 0.2 samples. This work showed that a single superconducting Tl-1212 phase was formed for x ≤ 0.1 samples. This work also showed that the internal lattice constrain which is the ratio of the lattice parameter (a/c) is important in improving the transition temperature of the Tl-1212 phase.

Magnetic phase diagram, magnetocaloric effect, and exchange bias in Ni43Mn46Sn11−xGax Heusler alloys

Abstract In this work, the effect of Ga substitution on the crystal structure, phase transitions, magnetocaloric effect, and exchange bias properties, was systematically investigated in Ni43Mn46Sn11−xGax alloys. With increasing Ga content, the Curie temperature of austenite slightly decreases, while the martensitic transformation temperature shifts to a higher temperature and finally disappears, due to the emergence of γ phase. Large low-field magnetic entropy changes around the martensitic transformation were observed as the transition from a paramagnetic martensitic phase to a ferromagnetic austenitic phase took place. Ni43Mn46Sn11 has a reentrant-spin-glass ground state, and Ga doping can enhance the antiferromagnetic interaction arising from lattice contraction, leading to close of intermediate ferromagnetic windows and establishment of canonical spin-glass for x > 2. Prominently, the zero-field-cooled exchange was achieved in the spin-glass region with 5 ⩽ x ⩽ 10 .

Effects of Ga substitution on electronic and thermoelectric properties of gapless semiconductor V3Al

Thermoelectric properties of the antiferromagnetic (AF) gapless semiconductor (GS) V3Al were optimized by substituting Al with the isoelectric element Ga in the D03 structure. Structural and mechanical stability, electronic structure and transport properties of V3Al1−xGax (x = 0.25, 0.5, 0.75 and 1) compounds have been studied based on first-principles calculations with the combination of the semi-classical Boltzmann theory and deformation potential theory. All the compounds are structurally and mechanically stable gapless semiconductors. The Ga substitution for Al leads to an appreciably decreased thermal conductivity and an undesirable decrease in power factor, but contributes more to the decreased thermal conductivity. Consequently, the figure of merit (zT) is effectively improved in V3Al0.75Ga0.25 and V3Ga compounds with respect to V3Al.

Effect of Ga substitution on low temperature transport and magnetic response of Ce75Al25 metallic glass

The low temperature transport and magnetic behavior of Ce75Al25-xGax (x=0, 2, 4 and 6 at. %) metallic glasses (MGs) have been investigated. The temperature dependence of the resistance shows that the temperature coefficient of resistance (TCR) changes with Ga content. The significant change in the magnetoresistance (MR) behaviour has been observed for these alloys. The alloys with x=2, 4 and 6 show a magnetic field tuned MR transition from positive to negative values at low temperature. The magnetization (M-H) curves of the MGs at 5 K exhibit no magnetic hysteresis and show paramagnetic characteristics. However, a curious type of hysteretic behaviour for Ce75Al25-xGax alloys in non-zero magnetic field has been observed. The hysteric field range has been found to shift to higher magnetic field with increase in the value of x. It has been suggested that the formation of nano-amorphous domains in the glassy matrix and the delocalization of 4f1 configuration of Ce atoms due to Ga substitution may result in the unusual transport behaviour of Ce-Al (Ga) MGs. These changes in the transport behaviour at low temperature have been discussed in terms of the competition between the Kondo effect and Ruderman–Kittel–Kasuya–Yoshida (RKKY) interaction. The genesis of hysteretic behaviour in M-H curve has been proposed to arise due to Anti-ferromagnetic screening interaction (AFSI) in two kinds of clusters.

Effects of Ga substitution in Ce:Tb3GaxAl5−xO12 single crystals for scintillator applications

Bulk single crystals of Ce-doped Tb3GaxAl5−xO12 (x = 0–4) were successfully synthesized by the floating zone method. The samples exhibit photoluminescence and scintillation with an intense broad emission due to the 5d–4f transitions of Ce3+ peaking around 550 nm as well as a few sharp peaks due to the 4f–4f transitions of Tb3+. Pulse height spectrum measurements under 137Cs γ-ray irradiation demonstrated a clear photoabsorption peak, in which the scintillation light yields were estimated to be 57,000 (x = 0), 28,000 (x = 1), 19,000 (x = 2), and 10,000 (x = 3) photons/MeV. Afterglow level can be suppressed with an appropriate addition of Ga, in which the optimum concertation is x = 2 leading an afterglow level of 23 ppm.

Systematic XPS study of gallium-substituted boehmite

Abstract: Ga-substituted boehmites were synthesized using a soft-chemistry route in the presence of poly(ethylene oxide) surfactant under hydrothermal conditions. The effect of Ga-substitution was studied by X-ray diffraction and X-ray photoelectron spectroscopy. Initial precipitates were amorphous (minor bayerite). After hydrothermal treatment, XRD showed broad reflections at low Ga-substation indicating low crystallinity and formation of pseudoboehmite. This was confirmed by high-resolution XPS of Al 2p, Ga 2p, and O 1s. The Al 2p binding energy of 74.03 eV was closer to boehmite than pseudoboehmite, probably caused by the Ga-substitution in the structure. The O 1s showed the presence of O, OH, and H2O. The ratio of (total O)/(Al + Ga) showed an excess of O as expected for pseudoboehmite. The ratio of (O + OH)/Al + Ga) was also slightly larger than the theoretical value of 2 for boehmite. High concentrations of added Ga (10, 20 %) resulted in amorphous material after hydrothermal treatment. Graphical Abstract: [Figure not available: see fulltext.]

Effect of Ga Substitution on the Γ3 Doublet Ground State in PrIr2Zn20

Electrical resistivity ρ, specific heat C, and magnetic susceptibility χ measurements are reported on PrIr2Zn20–xGax for x=0.5 and 1.0. On cooling, ρ(T)’s monotonically decrease to the residual values which are two orders of magnitudes larger than that of PrIr2Zn20. A broad hump in Cm(T)’s at around 10 K can be reproduced by the two-level model with the Γ3 doublet ground state and the Γ4 triplet excited state. The magnetic entropy release shifts to higher temperatures with increasing x. The increase in χ(T) at T < 5 K contrasts with the saturation of χ(T) for x=0. These observations indicate the splitting of the ground state doublet due to the lowering of the local symmetry at the Pr site by the Ga substitution.

Effect of Ga substitution on magnetocaloric effect in La0.7(Ba, Sr)0.3Mn1−xGaxO3 (0.0≤x ≤0.20) polycrystalline at room temperature

In this paper, we have investigated the effect of the non-magnetic (d10) Ga3+ doping on structural, magnetic and magnetocaloric properties of La0.7(Ba, Sr)0.3Mn1−xGaxO3 (x=0.0, 0.1 and 0.2) manganites prepared by solid state reaction method. The XRD study has revealed that all samples crystallized in the orthorhombic symmetry with Pnma space group. Magnetization measurements have confirmed that when the temperature increases, all the compositions exhibit a ferromagnetic to paramagnetic transition. The substitution of Mn by gallium Ga leads to a tune of the magnetic transition temperature (TC) to room temperature and the Curie temperature decreases from 314K for x=0.0 to 299K for x=0.2. Moreover, the obtained results of the magnetocaloric effect are in accordance with the reported values of other doped manganites, leading to the conclusion that our sample can be used as a magnetic refrigerant at room temperature.Finally, using Arrott plots, the phase transition from ferromagnetic to paramagnetic was found to be of a second order. The second order magnetic phase transition has been confirmed by the construction of the universal curve of the magnetic entropy change.

Phase Formation in the Rapidly Solidified Al70−xGaxPd13Mn17 Alloys

In the present investigation, the effect of Ga substitution at Al site on the phase formation and stabilization of decagonal quasicrystalline phase in the rapidly solidified Al70−xGaxPd13Mn17 alloys have been studied by employing X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive x-ray analysis. The as-cast and rapidly solidified alloys with x = 0, 2.5 and 5 have been investigated. The melt-spinning technique has been used for rapid solidification of the as-cast alloys. The alloys up to 5 at.% Ga exhibit the formation of small amount of icosahedral quasicrystalline phases along with major amount of decagonal phase in the rapidly solidied ribbons. The energy dispersive X-ray analysis investigations suggest the homogeneous presence of Ga in the quasicrystalline alloys.

Effects of Ga substitution on the structural and magnetic properties of half metallic Fe2MnSi Heusler compound

The so-called half-metallic magnets have been proposed as good candidates for spintronic applications due to the feature of exhibiting a hundred percent spin polarization at the Fermi level. Such materials follow the Slater-Pauling rule, which relates the magnetic moment with the valence electrons in the system. In this paper, we study the bulk polycrystalline half-metallic Fe2MnSi Heusler compound replacing Si by Ga to determine how the Ga addition changes the magnetic, the structural, and the half-metal properties of this compound. The material does not follow the Slater-Pauling rule, probably due to a minor structural disorder degree in the system, but a linear dependence on the magnetic transition temperature with the valence electron number points to the half-metallic behavior of this compound.

Effect of Ga Substitution on the Magnetic State of Delafossite CuCrO2 with Antiferromagnetic Triangular Sublattice

We investigated the effect of spin dilution on the structural and magnetic properties of delafossite CuCrO2 having an S=3/2 antiferromagnetic triangular lattice (ATL) by the substitution of Ga3+ for Cr3+ by measurements of magnetization. Spin defects introduced into Cr ATL layers blur the antiferromagnetic transition and induce a dimensional crossover of low-energy magnetic excitation in the residual Cr ATL region due to the reduction of inter-layer magnetic interaction, while accompanying an enhancement of a spin-glass component.

High-Temperature Thermoelectric and Microstructural Characteristics of Cobalt-Based Oxides with Ga Substituted on the Co-Site

The effects of Ga substitution on the Co-site on the high-temperature thermoelectric properties and microstructure are investigated for the misfitlayered Ca3Co4O9 and the complex perovskite-related Sr3RECo4O10.5 (RE = rare earth) cobalt-based oxides. For both systems, substitution of Ga for Co results in a simultaneous increase in the Seebeck coefficient (S) and the electrical conductivity (σ), and the influence is more significant in the high temperature region. The power factor (S 2 σ) is thereby remarkably improved by Ga substitution, particularly at high temperatures. Texture factor calculations using x-ray diffraction pattern data for pressed and powder samples reveal that the Ga-doped samples are highly textured. Microstructure observed by scanning electron microscopy shows very well-crystallized grains for the samples with Ga substitution for Co. Among the Ga-doped samples, Ca3Co3.95Ga0.05O9 shows the best ZT value of 0.45 at 1200 K, which is about 87.5% higher than the nondoped one, a considerable improvement.

Effect of Ga substitution on the crystallization behaviour and glass forming ability of Zr–Al–Cu–Ni alloys

The crystallization behaviour of melt spun Zr 69.5Al 7.5− x Ga x Cu 12Ni 11 ( x = 0–7.5; in at.%) metallic glasses has been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The DSC traces showed changes in crystallization behaviour with substitution of Ga. Formation of single nano-quasicrystalline phase by controlled crystallization of glasses has been found only for 0 ≤ x ≤ 1.5. Further increase of Ga content gives rise to formation of the quasicrystals together with Zr 2Cu type crystalline phase. In addition to this, the substitution of Ga influences the size and shape of nano-quasicrystals. The glass forming abilities (GFAs) of these metallic glasses were assessed by the recognition of glass forming ability indicators, i.e. reduced glass transition temperature ( T rg ) and supercooled liquid region (Δ T x ). The glass transition temperature ( T g ) has been observed for all the melt spun ribbons.

Effects of gallium on the structure and electrical properties of 0.65 Bi0.94La0.06) (GaxFe1-x)O3-0.35PbTiO3ceramics

Crystalline solutions of 0.65 Bi(0.94)La(0.06)) (Ga(x)Fe(1-x))O(3)-0.35PbTiO(3) Ceramics (BLGF-PT) for x = 0 and 0.05 have been fabricated by the solid-state reaction method. X-ray diffraction (XRD) was utilized to characterize the crystal structure and examine any possible impurities existing in the ceramics. The effects of Ga substitution on dielectric properties of the samples were studied at frequencies from 10(2) to 10(6) Hz over a temperature range from 20 to 620 degrees C. The results indicate that Ga modification can reduce the room temperature dielectric loss. The conduction mechanism of the material was investigated using ac conductivity. It is concluded that electrons originating from Fe(2+) and oxygen ion vacancies are the main charge carriers, and Ga doping could decrease the electronic conduction effectively. The frequency dependence of ac conductivity was found to follow Jonscher's universal power law.