Increasing Ga Content Research Articles

Development of novel scintillation and photo-conversion materials based on Gd3(Sc,Al,Ga)5O12:Ce single crystals grown by micro-pulling-down method

Luminescence, scintillation and photoconversion properties of Gd3Al5−x−yScxGayO12:Ce crystals, grown by the micro-pulling-down method, were studied upon substitution of Al for Sc3+ and Ga3+ in the x = 1–2;y = 1–3 ranges. A decrease of the band gap and crystal field strength occurs in these garnets with increasing Sc3+ and Ga3+ content, resulted in blue-shift and reduced thermal stability of Ce3+ emission. Lowering of the scintillation light yield of crystals by two times and scintillation decay kinetic acceleration from 97 to 27 ns is observed at increasing Ga content in the y = 1–3 range. Sc and Ga admixing increases the number of deep charge traps, which additionally deteriorate of crystals scintillation performance. Application of Gd3Al5−x−yScxGayO12:Ce crystals as phosphor converters of white LED was considered. Increasing the Sc3+ and Ga3+ content in crystals leads to linear blue shift of the converter emission and results in increasing the color temperature of LEDs from neutral to could white light.

Internal friction phenomena in a wide temperature range up to 800°C in long-term annealed Fe-(0−30) at% Ga alloys

The internal friction (IF) phenomena were systematically studied in a temperature range from room temperature (RT) to 800 °C for Fe-(0−30) at% Ga alloys annealed at 480 °C for 14 days, which include the magnetic-related high damping plateau (HDP) and the point of ferro-paramagnetic transition (Tc), grain boundary relaxations, Zener relaxations, and the IF peaks associated with phase transitions. It was found that the rapid decay temperature of the HDP decreases with increasing Ga content, which is consistent with the variation of the Curie point (Tc), and the HDP disappears when the Ga content is greater than 18 at%. In the long-term annealed Fe-30at%Ga alloy, a frequency-independent phase transition IF peak was observed and its mechanism was suggested as the phase transition of L12→A2/B2. The phase transitions in Fe-(0–30 at%)Ga alloys evaluated by the IF technique are in good agreement with the equilibrium phase diagram. In addition, a new relaxation peak was observed before the displacive phase transitions of L12→D019 and L12→A2/B2, and its mechanism could be related to Zener relaxation in the FCC structured L12 phase.

Effects of Ga content on the microstructure and mechanical properties of as-extruded Mg-xGa alloys

Microstructures and mechanical properties of the as-extruded Mg-xGa (x = 1, 3, 5, 7 wt%) alloys were investigated in the present work. Examination of as-extruded microstructures revealed that the grains were gradually refined from an average size of 45 µm (Mg-1Ga) to 15.7 µm (Mg-7Ga). Meanwhile, the volume fractions of Mg5Ga2 precipitates and dynamic recrystallization grains were significantly increased with increasing Ga content, and the texture was continuously weakened. The grain refinement and texture weakening were mainly ascribed to the increasing dynamic recrystallization stimulated by increasing Mg5Ga2 precipitates. The tensile test showed the as-extruded Mg-xGa alloys possessed both high strength and ductility that can meet the mechanical properties required by orthopedic implants. The tensile properties of as-extruded Mg-xGa alloys were gradually increased with increasing Ga content, reaching the highest yield strength of 166 MPa, ultimate tensile strength of 268 MPa, and elongation of 22.2% (Mg-7Ga). The enhanced tensile properties were benefited from a combination of grain refinement strengthening, solid solution strengthening and precipitation strengthening.

A Gallium-doped cement for the treatment of bone cancers. The effect of ZnO ↔ Ga2O3 substitution of an ionomeric glass series on the rheological, mechanical, pH and ion-eluting properties of their corresponding glass polyalkenoate cements

The primary treatment for patients suffering from bone cancers is resection of the tumour followed by reconstruction of the damaged bone. Despite the administration of post-operative chemotherapy, tumour recurrence continues to present itself as a severe complication leading to re-operation. Attempts to incorporate chemotherapeutic drugs into bone cements elicits local toxic effects on healthy bone, which could compromise implant fixation. Alternatively, the local administration of gallium (Ga) may prove to be more effective. This report considers the development of a Ga ionomeric glass series (0.48SiO2-0.355ZnO-0.06CaO-0.08SrO-0.02P2O5-0.005Ta2O5, with 0.01–0.05 mol% substitution for ZnO). X-ray Diffraction (XRD) confirmed the amorphous glass structure and Energy Dispersive x-ray Fluorescence (EDXRF) verified the successful addition of Ga into the glass series at the expense of Zinc (Zn). A Ga-GPC series was then formulated by mixing the glass particles with aqueous poly(acrylic) acid (PAA) and trisodium citrate (TSC). Fourier transform infrared (FTIR) spectroscopy demonstrated no structural changes to the GPC matrix with the incorporation of Ga. Measurements of the rheological properties demonstrated an exponential increase in setting time with increasing Ga content. Furthermore, the addition of 3 mol% Ga demonstrated deleterious effects on the GPC’s mechanical properties and an analysis of pH confirmed that it decreased with increasing Ga content, suggesting a reduction in glass reactivity and PAA cross-linking. Finally, inductively coupled plasma—optical emission spectrometry (ICP-OES) demonstrated the controlled release of Ga across the GPC series, which will prove beneficial to future in vitro studies.

Luminescence and scintillation properties of Gd3Sc2(Al3-xGax)O12:Ce (x = 1, 2, 3) garnet crystals

The luminescence and scintillation characteristics of Ce3+ - doped Gd3Sc2(Al3-xGax)O12 (x = 1, 2, 3) garnet crystals were investigated. The Ce3+ luminescence was blue-shifted with increasing Ga content due to the decrease of the crystal field strength. A decrease of Ce3+ luminescence intensity and luminescence decay time at high temperature was observed for all samples due to thermal ionization of the Ce3+ 5d1 excited levels. With increasing Ga content the decrease of thermal activation energies, determined from temperature dependence of decay times, was obtained. Both Gd3Sc2Al2GaO12:Ce and Gd3Sc2AlGa2O12:Ce samples exhibited a comparable light yield (LY) value of 24,000 photons/MeV while the latter sample showed faster scintillation decay time of 12 ns (11%) + 56 ns (89%) with respect to those of 55 ns (28%) + 105 ns (72%) for the former sample. An acceleration of scintillation decay time with an expense of LY value was also obtained for the Mg2+-codoped sample. At low temperature a decrease of scintillation yield was observed in correlation with the intense thermoluminescence peaks, attributing to the localization of electrons at intrinsic shallow traps.

Efficient adsorption of ciprofloxacin using Ga2S3/S-modified biochar via the high-temperature sulfurization

Ga2S3 and sulfur co-modified biochar (Ga/S-BC) composites were prepared for enhancing the adsorption of ciprofloxacin from sugarcane bagasse via the high-temperature sulfurization. In contrast with sulfur-modified biochar, Ga/S-BC exhibited the better adsorption capacity for ciprofloxacin removal. The increasing Ga content induced to the climbing and then declining adsorption activity of Ga/S-BC. Among these obtained Ga/S-BC composites, optimal 3-Ga/S-BC with a Ga content of 7.40% and surface area of 681.67 m2 g−1 exhibited the superior capacity of 330.21 mg g−1. The adsorption capacity of 3-Ga/S-BC declined to 301.66 mg g−1 after nine cycles. pH and inorganic salts also affected the adsorption capacity of 3-Ga/S-BC for ciprofloxacin removal. The adsorption isotherms of obtained Ga/S-BC composites were well described by Langmuir isotherm, and their adsorption kinetics were well estimated via second-order model. The adsorption performance of 3-Ga/S-BC in ciprofloxacin removal was a physisorption and spontaneous process.

Table-like magnetocaloric effect around room temperature of antiperovskite composite materials based on Mn3Sn1-xGaxC

The Mn3Sn1-xGaxC materials based on Mn3SnC with Sn partially replaced by Ga were prepared and their phase transitions were studied. With increasing Ga content, the Curie temperatures (Tc) of Mn3Sn1-xGaxC gradually decrease, but the large phase transition entropy (ΔS) is retained. Antiperovskite composite magnetic refrigerant was designed and synthesized by mixing the Mn3Sn1-xGaxC materials with different phase transition temperatures. The composite presents a nearly table-like magnetic entropy change (-ΔSM)-T curve near room temperature. Compared with Mn3SnC, the full width at half maximum (ΔTFWHM) of (-ΔSM)-T curves of the composite increased from 5 K to 44 K, and the refrigerant capacity (RCP) increased from 27.1 J/kg to 58.67 J/kg at 5 Tesla (T). This composite material is beneficial to magnetic Ericsson cycle, providing a new method for developing practical magnetic refrigerants in antiperovskite compounds.

New insights on photocatalytic hydrogen evolution of ZnFe2−xGaxO4 (0 ≤ x ≤ 2) solid solutions: Role of oxygen vacancy and ZnO segregated phase

The exponential increase in global energy and clean energy demands lead to the necessity for development of efficient photocatalyst for hydrogen evolution. Herein, photocatalytic hydrogen evolution activity with nano-structured ZnFe2-xGaxO4 (0 ≤x ≤ 2) solid solution samples synthesized by citrate-gel method at 550 °C is reported. The prepared materials have been characterized for their structure and optical properties. The formation of solid solution with spinel type structure in the complete range of composition and a systematically decreasing trend of unit cell parameters with increasing Ga3+ concentration is observed from powder XRD studies. The band gap of these solid solutions could be tuned from 1.9 to 3.1 eV by increasing the Ga3+ concentration. Without any co-catalyst, ZnFe2O4 shows poor catalytic activity (378μmolh−1g−1) for photocatalytic hydrogen evolution from water. Whereas its activity enhances with loading of co-catalyst and touches a maximum activity of 3089μmolh−1g−1 with loading 1 wt% of Pt. The catalytic activity increases systematically with increasing Ga concentration in the solid solutions and reaches to 3989μmolh−1g−1 for ZnGa2O4 nanomaterials. Electrochemical impedance spectroscopic and transient photocurrent measurements also support the observed increasing trend. The lower catalytic activity of ZnFe2O4 has been attributed to the faster e-h recombination due to lower band gap and inherent oxygen vacancies. A smaller amount of oxygen vacancies and segregated ZnO phase observed in Ga substituted ZnFe2O4 samples favor the e-h pair separation and that facilitate the hydrogen generation from water.

Structural and Magnetic Studies of Ga-doped Yttrium Iron Garnet

Ga-doped Yttrium Iron Garnet (Y3GaxFe5−xO12, Ga:YIG) was prepared by solid state reaction method and sintering at 1 300 °C. Rietveld analysis of X-ray diffraction patterns indicated that all samples crystallized in a single cubic structure (space group Ia-3d) with decreasing lattice constant as Ga concentration increased. SEM surface micrograph images of YIG samples showed highly compacted grains with small reduction in the grain size with increasing Ga concentration. Raman spectroscopy measurements confirmed the replacement of Fe3+ ions by Ga3+ ions in the garnet structure was revealed by the observed blue shifts in Raman spectra. The saturation magnetization decreased from 28.2 to 4.98 emu g−1 with increasing x from 0.0 to 1.0 due to the preferential substitution of Ga3+ ions for Fe3+ ions at tetrahedral sites. Room temperature Mossbauer spectra for the samples revealed a reduction of the hyperfine field values for octahedral and tetrahedral sites, and the development of additional components with increasing Ga concentration. Analysis of the magnetic data and Mossbauer spectra confirmed that spin canting in the substituted garnets plays an important role in explaining the observed reduction of the saturation magnetization as x increased.

The role of Ga in the microstructure, corrosion behavior and mechanical properties of as-extruded Mg–5Sn–xGa alloys

The effect of Ga element on microstructure, corrosion behavior and tensile mechanical properties of as-extruded Mg–5Sn–xGa (x = 0, 1, 2, 3, all in wt%) alloys was investigated using immersion test, electrochemical test and tensile test. The results show that the Mg2Sn and Mg5Ga2 particles are dynamically precipitated during extrusion process, and the volume fraction of Mg5Ga2 precipitates increases with increasing Ga content. The corrosion resistance of Mg–5Sn alloy in the immersion test is increased approximately by four times after adding 2 wt% Ga, due to the fact that the Ga element weakens the cathodic reaction, and more stable corrosion products are formed in the Ga-containing alloys in the inner corrosion layer. The tensile strength of investigated alloys is improved monotonously with increasing Ga content. The maximum elongation to fracture reaches up to 21.7% for Mg–5Sn–1Ga alloy due to the modified basal grain texture.

Electric, dielectric and magnetic properties of Ga, Er and Zn ion doped Fe2O3 thin films

Using a microscopic model we have investigated the electric, dielectric and magnetic properties of Ga, Er and Zn doped α-Fe2O3 thin films. The polarization P in Ga doped α-Fe2O3 decreases with increasing Ga content x, and increases with enhancing magnetic field h and decreasing film thickness N. In Ga doped hematite the dielectric constant ϵ shows a peak at TC. ϵ decreases with increasing h, indicating a strong magneto-dielectric effect. The contributions of the spin-phonon and phonon-phonon interactions below and above TC are considered. The dielectric constant in Ga, Er and Zn ion doped Fe2O3 can increase or decrease for different ions and different ion doping concentration. The ion doping dependence of the magnetization is also calculated.

Calcium Addition Improving Pectin Level in Oil Palm Seedlings (Elaeis guineensis Jacq.)

Long drought due to climate anomalies results in physiological damage to oil palm which is characterized by frond fracture to the decreased productivity. One of the efforts to increase the resistance of oil palm to drought is through the addition of calcium. This study aimed to determine the effect of calcium on hormonal changes (as secondary messenger), the rate of photosynthesis till the content of pectin as a reinforcing component of cell walls which is expected to reduce the risk of frond fracture due to drought. The treatment was arranged in factorial 3 x 4 in the random complete block design (RCBD) split-plot. The first factor was the dose of calcium application which was 0 (control/without calcium), 0,04 g, 0,08 g, and 0,12 g. The second factor was the intensity of drought stress consisting of severe stress, moderate stress, and control/field capacity with an intensity of one week after achieving target weight. Data that fulfilled the assumptions of homogeneity and normality were then analyzed using variance analysis at a level of accuracy of 5% and continued with DMRT. The results showed that calcium can increase the resistance of oil palm seeds through increased GA content, decreased ABA content and increased photosynthetic rates in all soil moisture conditions, but varied according to the intensity of drought.

Influence of Ga content and high temperature annealing on the short range order and magnetostriction of Fe–Ga single crystals

Large magnetostriction observed in Fe–Ga alloys makes them a very important class of alloys for use in a wide range of actuation and sensing applications. This study of quantitative measurements of short-range order (SRO) in a series of Fe–Ga alloys provides valuable insights into the correlations of magnetostrictive responses with an increase in the Ga concentration and annealing. A quantitative assessment of SRO in the first seven shells around an atom in as-grown and high-temperature annealed [001]-oriented Fe–Ga alloy single crystals with Ga contents in the range of 5–20 at. % was carried out using the diffuse peaks in the forbidden (100) peak region of the θ–2θ high-resolution x-ray diffraction pattern. The SRO parameter values obtained indicate that very little short-range ordering occurs in Fe–Ga alloys with low Ga concentrations and ordering is limited to the first few shells. With an increase in Ga content, SRO increases with ordering occurring out to further shells. High temperature annealing decreases SRO parameters to levels approaching random solid solution. The decrease in short-range ordering with high-temperature annealing correlates with the increase in magnetostriction and confirms the hypothesis that the difference in the extent of ordering is the source of the observed high sensitivity of magnetostriction to changes in thermal history.

Ga-Doped ZnO Nanostructured Powder for Cool-Nanopigment in Environment Applications.

Gallium (Ga) doped zinc oxide (ZnO) nanocrystals were successfully synthesized via a γ-radiation-assisted polymer-pyrolysis route. Ga doped ZnO samples with Ga and ZnO precursor salts with molar ratios of 0%, 3%, 5%, and 10% were produced. A γ-radiation dosage of 1.5 kGy was used for polymerization initiation during the sample preparation. The properties of the obtained nanocrystal samples were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR), UV-visible absorption, NIR-VIS-UV diffused reflectance, and high-resolution transmission electron microscopy (HR-TEM) characterization techniques. XRD results revealed the formation of ZnO nanocrystals with wurtzite structure for both Ga-doped and undoped ZnO samples. Noticeable increasing in the line broadening of the XRD peaks as well as pronounced decreasing of crystallite size were observed with the increasing Ga ratio in the samples. Optical peaks around Ga:ZnO samples showed a blueshift in the optical absorption peaks with increasing Ga content. These results are in good agreement with the dependency of crystallites size as well as grain size on Ga ratio obtained from XRD and TEM images, which make them fit well for the powder cool-pigment applications. The doped samples showed high values of NIR reflectance () with percentage varied from 84.25% to 89.05% that enabled them to qualify for cool-nanopigment applications. Furthermore, such doped samples registered low values of visible reflectance () that enabled to reduce the glare from the reflected visible sunlight.

Influence of Ga doping on structural, optical and electrical properties of transparent conducting SnO2 thin films

Different concentrations (1, 3, and 5 at %) of Ga doped SnO2 thin films were deposited onto glass substrate using sol-gel spin coating technique. X-ray diffraction studies revealed that all deposited films were exhibited tetragonal rutile structure of SnO2 with preferred orientation along (110) direction. The AFM micrographs shown that the grains are in spherical structure, and the average grain size decreased with the increase of Ga doped concentration in SnO2 lattice. In the visible light region, the average transmittance of pure SnO2 film found to be above 85%, whereas Ga doped SnO2 films were found to be a decrease of transmittance up to 74 % in 5 at % Ga doped SnO2 film. The optical band gap energy values were considerably decreased from 3.92 to 3.68 eV with the increase of Ga content. Further, the sheet resistance (Rsh) and resistivity (ρ) values were found to be increased with the increase of Ga doping. The efficiency parameter figure of merit (ϕ) was estimated for all deposited films and it was found to be decreased from 3.3 × 10-3 Ω-1 for pure SnO2 to 0.7 × 10-3 Ω-1 for 5 at % Ga doped SnO2 film.

Band Alignment at GaxIn1–xP/AlyIn1–yP Alloy Interfaces from Hybrid Density Functional Theory Calculations

The composition dependence of the natural band alignment at the GaxIn1–xP/AlyIn1–yP alloy interface is investigated via hybrid functional based density functional theory. The direct–indirect crossover for the GaxIn1–xP and AlyIn1–yP alloys is calculated to occur for x = 0.9 and y = 0.43. The calculated GaxIn1–xP/AlyIn1–yP interface band alignment shows a crossover from type‐I to type‐II with increasing Ga content x. The valence band offset is essentially positive irrespective of the alloy compositions, and amounts up to 0.56 eV. The conduction band offset varies between −0.85 and 1.16 eV.

Analysis of the gallium gradient in Cu(In1-xGax)Se2 absorbers by X-ray diffraction

In order to analyze why the CIGS (CuInGaSe2) - based solar cells efficiency decrease for wide band gap (high Ga content), we have performed a series of samples by PVD using the three stage process. The average compositions of our solar cells range from x = 0 to x = 0.88, as measured by X-ray diffraction. An important feature of this process is to create a double Ga gradient into the absorber, which contributes to improve efficiencies, and this has a major impact on the determination of the sample composition from x-ray diffraction data. We have developed a model in order to assess this impact and question the validity of the compositions extracted from x-ray data. This model allows to get some information about gradient shapes. Using our model, we have obtained some insights on the evolution of the gallium gradient in samples with increasing Ga content, and we determine that this gradient is less pronounced when increasing the amount of gallium. It is a well known fact that this gradient assists the extraction of photocreated carriers, and the modifications of the gallium profile that we have determined may explain, for some part, the degradation of solar cells efficiency for high gallium compositions.

Synthesis and Characterization of CuIn1-xGaxSe2 Semiconductor Nanocrystals.

In this paper, the synthesis and characterization of CuIn1−xGaxSe2 (0 ≤ x ≤ 1) nanocrystals are reported with the influences of x value on the structural, morphological, and optical properties of the nanocrystals. The X-ray diffraction (XRD) results showed that the nanocrystals were of chalcopyrite structure with particle size in the range of 11.5–17.4 nm. Their lattice constants decreased with increasing Ga content. Thus, the x value of the CuIn1−xGaxSe2 nanocrystals was estimated by Vegard’s law. Transmission electron microscopy (TEM) analysis revealed that the average particle size of the nanocrystals agreed with the results of XRD. Well-defined lattice fringes were shown in the TEM images. An analysis of the absorption spectra indicated that the band gap energy of these CuIn1−xGaxSe2 nanocrystals was tuned from 1.11 to 1.72 eV by varying the x value from 0 to 1. The Raman spectra indicated that the A1 optical vibrational mode of the nanocrystals gradually shifted to higher wavenumber with increasing x value. A simple theoretical equation for the A1 mode frequency was proposed. The plot of this equation showed the same trend as the experimental data.

Comparison of Triethylgallium and Trimethylgallium Precursors for GaInP Nanowire Growth

Nanowire (NW) arrays containing a top segment of GaxIn1–xP are investigated, comparing NWs grown using two different Ga precursors, trimethylgallium (TMGa) and triethylgallium (TEGa). TMGa is the precursor commonly used for the particle‐assisted vapor–liquid–solid (VLS) growth of GaxIn1–xP NWs. However, it shows inefficient pyrolysis at typical NW growth conditions. The use of the alternative precursor TEGa is investigated by making a direct comparison between NWs grown using TEGa and TMGa at otherwise identical growth conditions. Growth rates, resulting NW materials composition, and time‐resolved photoluminescence (TRPL) lifetimes are investigated. With increasing Ga content of the NWs, the TRPL lifetimes decrease, indicating trap states that are associated with GaP. Somewhat longer TRPL lifetimes for the samples grown using TEGa indicate a lower concentration of deep trap states. For doped NWs, it is found that the strong effect of the p‐type dopant diethylzinc (DEZn) on the NW composition, observed for GaxIn1–xP NWs grown using TMGa, is absent when using TEGa.

Desarrollo de Zeolitas Ga-ZSM-11 para la Síntesis de Ácido Láctico

En el presente trabajo se analiza la influencia de la temperatura de reacción y del contenido de galio en la zeolita ZSM-11 (estructura MEL) en la obtención de ácido láctico a partir de dihidroxiacetona (DHA). El catión metálico fue incorporado por impregnación húmeda en distintas concentraciones (~ 2-10% p/p). La estructura ZSM-11 se confirmó por DRX para todas las muestras, en tanto que en los materiales impregnados la cristalinidad disminuyó a medida que se incrementó la cantidad del catión incorporado al catalizador. Por el método BET se analizó el área superficial y se encontró que la misma disminuye al aumentar el contenido de Ga incorporado. Mediante FTIR con adsorción de piridina se determinó la cantidad, fuerza y relación de sitios ácidos. El estudio por TPR señaló la reducción de las especies superficiales vecinas a los enlaces Ga-O y la reducción de Ga+3 a Ga+. El análisis de reflectancia difusa de UV-visible indicó la dispersión de los posibles aglomerados de óxidos de galio. Dichos materiales exhibieron un buen desempeño catalítico en la conversión de dihidroxiacetona (DHA) a ácido láctico, molécula plataforma de gran interés actual