Increase In GA3 Research Articles

Cr3+‐Cr3+ Ion Pair Induced Fast Energy Migration in Cr3+ Doped Na‐β‐Al2O3 Ultra‐Wide Near‐Infrared Phosphors for NIR Spectroscopy Application

AbstractTechnological progress has promoted the development of ultra‐wide near‐infrared (NIR) luminescent materials as a new NIR light source. The ultra‐wide near‐infrared (NIR) emission in Na(Al,Ga)11O17:xCr3+(NAGO:xCr3+) phosphors is achieved by constructing unique Cr3+‐Cr3+ion pair confined structure. The Cr3+‐Cr3+ ion pairs can be observed at a low concentration of Cr3+ ions(x = 0.04), the increase of Ga3+ ion would promote the formation of Cr3+‐Cr3+ ion pairs, thereby effectively enhancing the energy migration process from high‐energy Cr3+ ions to low‐energy Cr3+ ones. Herein, the full width at half maximum can be finely adjusted in a wide range from 17 to 223 nm, while the emission peaks can shift from 704 to 860 nm. NAGO:xCr3+ exhibits the longest‐wavelength emission in the known Cr3+‐doped galliates and aluminates phosphors. The study further reveals the inherent mechanism of affect on the photoluminescence properties for Cr3+‐Cr3+ ion pairs. The quantum efficiency of optimal NaAl11O17:0.004Cr3+ (sharp emission) and NaGa11O17:0.02Cr3+(ultra‐wide emission) samples reaches 87.6% and 46.6% with high thermal stability (84.47% and 67.52%@150 °C), respectively. The comprehensive properties are excellent among known phosphors with similar property. Multifunctional applications of NAGO:xCr3+ in agricultural production, quality inspection, and imaging fields are also demonstrated.

Cationic substitution engineering achieves higher efficiency and thermal stability of Cr3+-activated phosphor for pepper (Capsicum annuum L.) development

Nowadays, near-infrared phosphor-converted light emitting diodes (NIR pc-LEDs) attract wide attention since the NIR spectroscopy technique can exert itself in many fields. However, most of the developed NIR phosphors are still not commercially viable, because of low internal/external quantum yield and poor thermal resistance. Therefore, it is urgent to develop an efficient irradiance and thermal stable NIR phosphor. In this work, the new GdAl3-x-yGay(BO3)4: xCr3+ phosphors, compared with the original phosphor (x = 0.03, y = 0), when x = 0.03, y = 0.2, the luminescence intensity increased by 2.1 times, and the thermal resistance jumped from 92.0% to 96.7%. At the same time, with the increase of Ga3+, the spectra were gradually red shifted and FWHM widened, attributing to the nephelauxetic effect and the electron-phonon coupling effect enhanced, respectively. Particularly, under 420 nm excitation, the internal and external quantum yield of GdAl2.77Ga0.2(BO3)4: 0.03Cr3+ were 93.4% and 35.5%, respectively, which is higher than the previous research. The electric-optical conversion efficiency of the pc-LED was 10.76%. Finally, the phosphor application experiments revealed that the prepared phosphor has a very high commercial application potential.

Thermally enhanced upconversion luminescence of Cr3+ in Er3+-Yb3+-Cr3+ tri-doped garnet phosphors for sensitive optical thermometry

Luminescence thermometry is strongly desired in many fields due to the capability of remote temperature measurement with fast response and high spatial resolution. For developing excellent luminescence thermometer, we systematically investigated the upconversion (UC) emissions from Er3+-Yb3+-Cr3+ tri-doped garnet-structured phosphors under the excitation of 980 nm laser. The influence of Ga3+/Al3+ dopant ratio in Y3Al5-xGaxO12 on the UC luminescence was studied in detail by the X-ray diffraction patterns, Raman spectra, FT-IR spectra and Judd-Ofelt theory. Research revealed that the increase of Ga3+ doping content could reduce the symmetry of rare earth (RE) ions site and simultaneously weaken the nonradiative relaxations, favoring the RE luminescence and the subsequent energy transfer (ET) from RE to Cr3+. More importantly, because of the thermally strengthened ET from Er3+ ions, about 27-fold enhancement in Cr3+ UC luminescence was successfully achieved within Er3+-Yb3+-Cr3+ tri-doped Y3Ga5O12 as temperature ascended from 303 to 873 K, which consequently leaded to the emission color switching in response to temperature change. These advances in the as-prepared garnet phosphors provide potential opportunity for vision-guided temperature sensing with high sensitivity (∼ 4.38% K−1) and low measurement uncertainty (∼ 0.29 K).

Investigation of crystal structure, electrical and dielectric response of Ga3+ substituted Sr–Ni Y-type hexaferrites as a suitable material for high frequency applications

Technology important ferrites ceramic Sr2Ni2GaxFe12-xO22 (x = 0.00, 0.2, 0.4, 0.6, and 0.8) samples were produced using sol-gel auto combustion route. Structural, electrical, dielectric, and magnetic parameters were identified by substituting Ga3+ at the Fe3+ site. It was recognized that an increase of Ga3+ content in (Sr2Ni2GaxFe12-xO22) ceramic samples first decreased, then increased lattice parameters, and the density of samples was observed. This is because of the ionic radii and atomic weight of Ga3+ and Fe3+ cations. FTIR spectra show two characteristic absorption bands at 444-513 cm−1 caused by metal-oxygen vibrations. Due to the contribution of smaller grains of samples, the higher values of resistivity were observed, which vary from 3.78 × 1010 (Ω cm) to 1.13 × 1011 (Ω cm) by the substitution of Ga3+ ions at the octahedral site. The activation energy was measured between 0.20 and 0.61 eV. The dielectric response of Ga3+ substituted ferrite ceramic samples were studied in the 1 MHz-6 GHz frequency region. The Maxwell-Wagner bilayer model studied the effect of polarization with applied frequency on dielectric parameters. With the substitution of Ga3+, minimal losses in the range 0.34–0.44, about 6 GHz, and a high Q-value of about 10,000 were observed for each sample. In impedance spectroscopy analysis Cole-Cole plots confirm that the dielectric response is because of the influence of grain boundaries. The substitution of Ga3+ enhances saturation magnetization (68.20–71.78 emu/g) while coercivity decreases (655.86–507.86 Oe). In the present finding, the low dielectric loss, moderate permittivity, high value of the Quality factor, and very high value of resistivity of about 1.13 × 1011 that reduces the eddy current losses suggested that these materials are appropriate candidates for many high-frequency applications such as multilayer chip inductor, dielectric resonators, power applications, and microwave devices.

Effect of Ga3+ ions substitution on the garnet phase stability and photoluminescence properties of GLAGG: Ce solid solutions prepared via sol-gel method

In the present work, Ce3+ activated gadolinium lutetium aluminium gallium garnet (GLAGG) solid solutions with chemical formula Gd2.67Lu0.3Al5-xGaxO12: Ce0.03 (x ​= ​0, 0.25, 0.5, 0.75 and 1) have been successfully synthesized using the sol-gel method. The samples were analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectrometry and photoluminescence spectroscopy in order to investigate the effect of Ga3+ substitution on the garnet phase stability, morphology and luminescence properties. The XRD analysis revealed that the garnet phase is very sensitive to Ga3+ content. When x ​= ​0 and 0.25, the garnet structure is the predominant phase with the presence of a secondary perovskite phase (GAP). The percentage of GAP phase decreased from 21.2% to 6.2% when Ga3+content increased from x ​= ​0 to x ​= ​0.25. A more stable garnet phase was obtained for solid solutions prepared with x ​≥ ​0.5. FESEM micrographs showed that all samples have porous plates-like morphology. All solid solutions showed green-yellow emission with higher emission observed for the sample prepared with x ​= ​0.5. The increase in Ga3+ content induced a blue shift in the emission band of 5d1 level and a red shift in the 5d2 level.

Investigation of Ga doping for non-stoichiometric sodium bismuth titanate ceramics

The electrical properties of Ga3+ doping Na0.5Bi0.5TiO3-based oxygen ionic conductors were studied. The Na0.52Bi0.47Ti1−xGaxO3−δ (x = 0, 0.01, 0.015, 0.02) samples were fabricated by the means of traditional solid-state reaction. The results of AC impedance measurements showed that the bulk conductivity of Na0.52Bi0.47Ti1−xGaxO3−δ samples decreased monotonously with the increase of Ga3+ doping concentration. At 673 K, the bulk conductivity of the Na0.52Bi0.47Ti0.98Ga0.02O3−δ sample is 7.19 × 10–4 S/cm, which is lower than that of the Na0.52Bi0.47TiO3−δ sample under the identical test temperature. The highest total conductivity emerged in the Na0.52Bi0.47Ti0.99Ga0.01O3−δ (x = 0.01) sample with 1.387 × 10–4 S/cm at 623 K, which demonstrated that the slight Ga3+ doping supported the enhancement of the total conductivity. A relaxation peak was observed in Na0.52Bi0.47Ti1−x GaxO3−δ compounds. As the Ga3+ ions were introduced into the Na0.52Bi0.47TiO3−δ compound, there was an increasing trend of the relaxation activation energy educed by the internal friction test. In addition, the oxygen relaxation height decreased with Ga3+ doping, which suggested that the introduction of Ga3+ ions resulted in the decrease of mobile oxygen vacancy.

Responses of Autumn Phenology to Climate Change and the Correlations of Plant Hormone Regulation

Current understanding of autumn phenological responses to climate change in deciduous tree species remains limited, mainly due to the difficulties in defining autumn events and the lack of knowledge about its mechanism. Here we applied a method based on measuring chlorophyll A (Chla) content in leaf tissue during the entire autumn senescence processes to appropriately quantify autumn phenological processes. Beginning of leaf coloring could be defined as when about 50% of the Chl was lost. End of leaf coloring could be defined as when about 95% of the Chl was lost. Then the mechanism behind the timing of autumn senescence responses to climate change through hormone regulation was studied for the first time. Four dominate deciduous tree species with representative senescence type (Salix babylonica, Ginkgo biloba, Acer mono, Cotinus coggygria) were chosen as the subject of study. Variations in climate factors (temperature, day length, precipitation, humidity) were recorded and nine major endogenous hormones (IAA, IPA, ZR, DHZR, GA3, GA4, ABA, MeJA, BR) in leaf tissues were monitored during the entire autumn senescence processes. The experimental results verified temperature and day length are the major climate factors affecting autumn phenology. Low temperature and short day length could result in the decrease of ZR level and the increase of ABA level in leaf tissue, which directly trigger/promote senescence. Meanwhile, low temperature and short day length could cause the decrease of MeJA level and the increase of GA3 and GA4 level, which regulate the timing of autumn senescence indirectly through ZR, ABA, and IAA. Our study improves the understanding of autumn phenological response to climate change in deciduous trees.

Evaluation of sucrose and GA3 in an in vitro shoot culture of Alpinia purpurata (Zingiberaceae)

Alpinia purpurata is an ornamental plant species native to the Asia-Pacific with commercial potential due to its red inflorescence adapted to the northern Colombian coast; however, the lack of propagation protocols hinders commercial cultivation. To adjust a micropropagation protocol for clonal plant material production, the aim of this study was to evaluate the effect of sucrose and gibberellic acid (GA3) in the culture medium on the number of new shoots per explant, shoot length, root number, root length and number of leaves. Explants were cultured in semisolid MS (Murashige & Skoog) medium with sucrose (30, 45 and 60 mg/L) and GA3 (0.0; 0.25; 0.5; 0.75 and 1.0 mg/L). A factorial experimental design with two factors was employed, with 15 treatments, 10 replicates per treatment and 150 experimental units distributed with a completely randomized design. Cultures were stored five weeks at 25 °C with a 12 h photoperiod (40 μmol m-2 s-1). Anova and Tukey’s test allowed detecting the statistical effects of sucrose and GA3 supply for all variables. An increase in sucrose concentration resulted in a higher number of shoots, while an increase in GA3 induced longer shoots. Root length and leaf number decreased as GA3 and sucrose increased.

Response of axillary bud development in garlic (Allium sativum L.) to seed cloves soaked in gibberellic acid (GA3) solution

Gibberellins (GAs) are important phytohormones that regulate many developmental processes in plants. Clove, as the reproductive organ of garlic, dramatically affected garlic bulb development. Considering the potential of gibberellins in plant development and our previous studies, we investigated the effect of soaking two types of seed cloves (seed clove-I: without root/shoot sprouting; seed clove-II: with root/shoot sprouting) in GA3 solution on axillary bud development and examined the effect of soaking seed cloves in GA3 solution on bulb development, phytohormone level and sugar content in this study. Results indicated seed clove types, soaking liquids and their interaction significantly affected the number of cloves per bulb and the rate of single-clove bulb. Moreover, soaking seed cloves in 1 mmol L−1 GA3 solution for 24 h not only promoted axillary bud formation and secondary plant growth (equal to tillering or branching), but also slightly increased the number of cloves per bulb and changed bulb structure with a low yield and marketable quality. On the 40th day after GA3 treatment (at axillary bud outgrowth stage), zeatin riboside (ZR) and soluble protein in stem were sharply increased with the increase of GA3, sucrose, fructose and soluble protein in leaf. However, GA3, indole-3-acetic acid (IAA), soluble sugar and sucrose in stem (3.52 ng g−1 fresh weight (FW), 19.88 ng g−1 FW, 237.3 mg g−1 FW, and 8.24 mg g−1 FW, respectively) were significantly decreased on the 40th day after GA3 treatment, compared to the control of water treatment (5.56 ng g−1 FW, 32.96 ng g−1 FW, 263.6 mg g−1 FW, and 10.37 mg g−1 FW, respectively). To our knowledge, these novel results indicate seed cloves soaked in GA3 solution promotes axillary bud formation and outgrowth that caused the changes in plant architecture and bulb structure. Meanwhile, our findings suggest that the level of endogenous plant hormone (GA3, IAA and ZR) cooperates with the content of sugar (sucrose and fructose) in leaf and stem to regulate axillary bud outgrowth in garlic.

Gibberellic Acid Usage Relieving Salinity Adverse Effects on Growth, Flowering and Bulb Production of Tuberose Plants (Polianthes tuberosa, L.)

The current research was carried out during two successive seasons of 2017 and 2018 at the Nursery of Ornamental plants, Fac. of Agric., Minia University, to explore alleviating side effects of soil salinity on growth, flowering and bulb production of tuberose plants by usage of gibberellic acid (GA3). Different vegetative growth traits, flowering parameters and bulb production aspects were greatly and gradually reduced parallel to the increase in soil salinity level with the least values being given due to highest salinity level. In addition, flowering date was delayed due to salinity treatments. By contrast, all these traits were enhanced upward according to the increase in GA3 (50 or 100 ppm) concentration including earlier flowering. It could be concluded that, the counteraction between GA3 and salinity, for bulb production traits was significant in both seasons. The combined treatment of high salinized/high GA3 was capable of giving similar to those given by the un-salinized/un-gibberellin treatment. The role of GA3, when applied at 100 ppm to highly salinized soils (1.2%), in enhancing number, fresh weight and dry weight of daughter bulbs give rise to increases of 71.3, 40.8 and 37.8% in the first season and 66.7, 48.7 and 56.0%, in the second season, respectively. Therefore, tuberose plants could be produced, under salt affected soils, by the use of GA3 which counteracted hindered effects of salinity on plant growth and flowering. The application of such growth regulator resulted in growth, flowering and bulb productivity values nearly equalized those given by control treatments.

High-frequency absorption properties of gallium weakly doped barium hexaferrites

ABSTRACTThe BaFe12-xGaxO19 (x < 1.2) hexaferrites were synthesised by usual ceramics technology. The Bi2O3 additive in the amount of 3 wt% was applied. The features of crystal structure and unit cell parameters were refined using powder X-ray diffraction at 300 K. It is shown that with the substitution level increase the parameters of unit cell monotonically decrease. The magnetisation and susceptibility versus temperature and field for these solid solutions were investigated by the vibration magnetometry method. The concentration dependence of the main magnetic parameters is constructed. It is shown that with the substitution level increase the magnetic parameters monotonically decrease. The microwave properties of the samples including the external magnetic bias field are also investigated at 300 K. It is shown that with the increase of Ga3+ concentration from x = 0.1 to x = 0.6 the frequency value of natural ferromagnetic resonance (NFR) decreases in the beginning, and at further increase in concentration up to x = 1.2 it increases again. With the increase in Ga3+ concentration, the line width of the NFR increases that indicates the increase of frequency range where there is an intensive absorption of electromagnetic radiation (EMR). At the same time, the peak amplitude of the resonant curve changes slightly. The frequency shift of NFR in the external magnetic bias field takes place more intensively for the samples with small Ga3+ concentration. It is shown the prospects of use of the Ga-substituted barium hexagonal ferrite as the material effectively absorbing the high-frequency EMR.

Elucidation of the mechanism of reflowering in tree peony (Paeonia suffruticosa) ‘Zi Luo Lan’ by defoliation and gibberellic acid application

In this study, the reflowering mechanism of tree peony (Paeonia suffruticosa ‘Zi Luo Lan’) after defoliation and gibberellic acid (GA) application (autumn-flowering treatment) was investigated by monitoring the morphological changes, measuring the endogenous GA3 and abscisic acid (ABA) contents, and determining the expression patterns of six GA- and two ABA-related genes. The results show that autumn-flowering treatment induced tree peony reflowering in autumn, which was accompanied by nutrient absorption in buds. The application of exogenous GA3 induced a simultaneous increase in GA3 and decrease in ABA levels, suggesting that the high ratios of GA3/ABA may play a key role in inducing tree peony reflowering. RT-qPCR analysis shows that PsCPS and PsGA2ox were significantly induced and inhibited by GA3 application, respectively, which supports the hypothesis that GA3 treatment induces endogenous GA3 production. In addition, GA3 treatment inhibited the expression of the PsGID1c, but its effect on PsGAI1 was limited, whereas the expression of PsGAMYB could be GA- or ABA-related. Furthermore, autumn-flowering treatment significantly inhibited the expression of PsNCED and PsbZIP, which coincides with the observed changes in ABA levels. Therefore, we postulate that autumn-flowering treatment induces tree peony reflowering by inhibiting the function of ABA accumulation and signaling.

Influence of Mg2+/Ga3+ doping on luminescence of Y3Al5O12:Ce3+ phosphors

Mg2+/Ga3+ doped Y3Al5O12:Ce3+ phosphors were synthesized through a solid state reaction. The phase and luminescent of the synthesized phosphors were investigated. For Ga3+ codoped Y2.96Ce0.04Al(5−x)GaxO12 phosphors, the emission intensity increases with the increase of Ga3+ concentration up to Y2.96Ce0.04Al4.80Ga0.20O12 and then decreases with a further increase of Ga3+ concentration, but the emission peak shifts to shorter wavelength continuously in the Ga3+ doping concentration range of 0.05–0.25. For Mg2+/Ga3+ codoped Y2.96Ce0.04Al(4.8−y)Ga0.20MgyO12 phosphors, the emission intensity decreases and the emission peak shifts to longer wavelength continuously in the Mg2+ doping concentration range of 0.02–0.12. The emission spectra of Y2.96Ce0.04Al(4.8−y)Ga0.20MgyO12 phosphors demonstrate that the codoped Mg2+/Ga3+ ions not only induce the enhancement of Y2.96Ce0.04Al5O12 emission intensity but also lead to the red shift of Y2.96Ce0.04Al5O12 emission peak. The decay lifetimes decrease in Mg2+/Ga3+ codoped Y2.96Ce0.04Al5O12 phosphors due to defects formed by substitutions of Y3+ by Mg2+/Ga3+.

Phytohormone Signaling of the Resistance to Plum pox virus (PPV, Sharka Disease) Induced by Almond (Prunus dulcis (Miller) Webb) Grafting to Peach (P. persica L. Batsch).

Plum pox virus (PPV, sharka) is a limiting factor for peach production, and no natural sources of resistance have been described. Recent studies, however, have demonstrated that grafting the almond cultivar “Garrigues” onto the “GF305” peach infected with Dideron-type (PPV-D) isolates progressively reduces disease symptoms and virus accumulation. Furthermore, grafting “Garrigues” onto “GF305” prior to PPV-D inoculation has been found to completely prevent virus infection, showing that resistance is constitutive and not induced by the virus. To unravel the phytohormone signaling of this mechanism, we analyzed the following phytohormones belonging to the principal hormone classes: the growth-related phytohormones cytokinin trans-zeatin (tZ) and the gibberellins GA3 and GA4; and the stress-related phytohormones ethylene acid precursor 1-aminocyclopropane-1-carboxylic acid (ACC), abscisic acid (ABA), salicylic acid (SA), and jasmonic acid (JA). PPV inoculation produced a significant increase in GA3 and ABA in peach, and these imbalances were related to the presence of chlorosis symptoms. However, grafting “Garrigues” almond onto the PPV-inoculated “GF305” peach produced the opposite effect, reducing GA3 and ABA contents in parallel to the elimination of symptoms. Our results showed the significant implication of SA in this induced resistance in peach with an additional effect on tZ and JA concentrations. This SA-induced resistance based in the decrease in symptoms seems to be different from Systemic Acquired Resistance (SAR) and Induced Systemic Resistance (ISR), which are based in other reactions producing necrosis. Further studies are necessary, however, to validate these results against PPV-D isolates in the more aggressive Marcus-type (PPV-M) isolates.

Synthesis and luminescence properties of novel Ce3+-doped Yb3Al5–xGaxO12 garnets with very fast decay time

A novel series of Ce3+-doped Yb3Al5–xGaxO12 (x = 0, 1, 2, 3, 4, 5) powders of ytterbium aluminum gallium garnets were synthesized by high temperature solid-state reaction in a carbon reducing atmosphere. The ytterbium aluminum garnets were characterized by X-ray powder diffraction, UV-Vis diffuse reflectance spectra, photoluminescence spectra and decay curves. Moreover, the substitution effect for the Al3+ sites with Ga3+ in 0.5 at%Ce:Yb3Al5–xGaxO12 (x = 0, 1, 2, 3, 4, 5) garnets were discussed. With the increase of Ga3+ ion concentration, the visible absorption peaks within 400–450 nm have blue shift phenomenon, while the absorption peaks in the range of 330–350 nm and the absorption band edge red shifts. Furthermore, the short decay times are very short with less than 10 ns due to the Yb3+ + Ce3+ → Yb2+ + Ce4+ electron transfer reaction.

Preparation and luminescence properties of Y3−yAl5−xGaxO12:Ce3+y phosphors

Y3−yAl5−xGaxO12:Ce3+y phosphors were prepared by high temperature solid state reaction method. The crystal structures, the influence of Ga3+ concentration on the photoluminescence (PL), cathodoluminescence, thermal stability and morphology of the phosphors were studied in detail. The results indicated that diffraction angle of the samples decreased gradually with the increase of Ga3+ ions content in XRD pattern. The emission peak of the spectra show a progressive blue-shift, the intensity increased first and then decreased and the optimal Ga3+ concentration in Y2.94Al5−xGaxO12:Ce3+0.06 phosphors is x = 0.75. The critical concentration of Ce3+ in YAGG:Ce3+ phosphors is affected with the ratio of Ga3+ to Al3+ and the Y2.9Al4.25Ga0.75O12:Ce3+0.1 phosphor showed the best performance on PL. However, the optimum concentration of Y3−yAl5−xGaxO12:Ce3+y phosphors is x = 1.5 and y = 0.04 when they were excited by cathode ray.

Microwave properties of the Ga-substituted BaFe12O19 hexaferrites

The crystal structure features and the unit cell parameters were refined using the powder x-ray method for the solid solutions BaFe12−xGaxO19 (x = 0.1–1.2) barium hexagonal ferrites of M-type at 300 K. With increase of substitution level the unit cell parameters monotonically decrease. The temperature and field dependences of the specific magnetization were investigated by the vibration magnetometry method. The concentration dependence of the TC Curie temperature as well as the MS spontaneous specific magnetization and the HC coercive force at 300 K is constructed. With increase of substitution level the magnetic parameters monotonically decrease. The microwave properties of the considered solid solutions in the external magnetic bias field are also investigated at 300 K. With increase of Ga3+ concentration from x = 0.1 to x = 0.6 the frequency value of the natural ferromagnetic resonance (NFR) decreases in the beginning, and at further increase in concentration up to x = 1.2 it increases again. With increase in Ga3+ concentration the line width of the NFR increases that indicates the increase of frequency range where there is an intensive absorption of electromagnetic radiation (EMR). At the same time the peak amplitude of the resonant curve changes slightly. The frequency shift of the NFR in the external magnetic bias field takes place more intensively for the samples with small Ga3+ concentration. It is shown the prospects of use of the Ga-substituted barium hexagonal ferrite as the material effectively absorbing the high-frequency EMR.

Magnetic, dielectric and microwave properties of the BaFe12-xGaxO19 (x ≤ 1.2) solid solutions at room temperature

The BaFe12-xGaxO19 (x=0.1–1.2) solid solutions of the barium hexagonal ferrite of M-type were synthesized and attested by the powder X-ray diffraction method at 300K. The unit cell parameters were refined. With increase of substitution level the parameters of unit cell monotonically decrease. These samples were investigated by the vibration magnetometry method. With increase of substitution level the magnetic parameters monotonically decrease. The concentration dependence of the TC Curie temperature as well as the MS spontaneous specific magnetization and the HC coercive force at 300K is constructed. The microwave properties of the considered samples in the external magnetic bias field were also investigated at 300K. It is shown that with increase of Ga3+ concentration from x=0.1 to x=0.6 the frequency value of the natural ferromagnetic resonance decreases in the beginning, and at further increase in concentration up to x=1.2 it increases again. With increase in Ga3+ concentration the line width of the natural ferromagnetic resonance increases that indicates the increase of frequency range where there is an intensive absorption of electromagnetic radiation. At the same time the peak amplitude of the resonant curve changes slightly. The frequency shift of the natural ferromagnetic resonance in the external magnetic bias field takes place more intensively for the samples with small Ga3+ concentration. It is shown the prospects of use of the Ga-substituted barium hexagonal ferrite as the material effectively absorbing the high-frequency electromagnetic radiation.

Isomorphism in the Bi1.8Fe1.2(1−x)Ga1.2xSbO7 pyrochlores with spin glass transition

A series of Bi1.8Fe1.2(1−x)M1.2xSbO7 (M = Ga, Al) compositions with substitution of Fe3+ for diamagnetic Ga3+ and Al3+ has been synthesized and characterized by XRD, Mössbauer spectroscopy and magnetic measurements. X-ray diffraction analysis indicate that the Bi1.8Fe1.2(1−x)Ga1.2xSbO7 (x = 0–1) at the whole x range and Bi1.8Fe0.84Al0.36SbO7 (x = 0.3) are solid solutions of pyrochlore structure. With an increase of Ga3+ content the substitution of Fe3+ for Ga3+ occurs disproportionally over A- and B-sites while Al3+ ion incorporates entirely on B-site. Magnetic measurements showed that all studied compositions fall into the category of disordered, magnetically frustrated materials and at T ≤ 13 K undergo spin-glass transition. The spin-glass phases have a striking sensitivity to substitution of Fe3+ for Ga3+ or Al3+. The comparison of the magnetic behavior of Ga- and Al-containing pyrochlores revealed that, most likely, freezing temperature is governed by Fe3+ ions residing especially on octahedral B-sites.

Influence of gallium on the growth and photoelectrochemical performances of AgIn5S8 photoelectrodes

Ga-doped AgIn5S8 films are grown on indium–tin-oxide-coated glass substrates using chemical bath deposition. The structural, optical, and photoelectrochemical properties of the samples are investigated as a function of the [Ga]/[(Ga+In)] molar ratio in the precursor solution. X-ray diffraction pattern of a cubic AgIn5S8 phase appears for the undoped sample. With increasing [Ga]/[(Ga+In)] molar ratio in the precursor solution, the diffraction peaks of the samples shift to higher angles. Images from a scanning electron microscope reveal a change in the microstructures of samples from diamond-like to plate-like with an increase in Ga3+ ions in the precursor solution. The thicknesses and direct and indirect band gaps of the samples, determined from surface profile measurements and transmittance and reflectance spectra, are in the ranges of 672–275nm, 1.91–1.85eV and 1.68–1.50eV, respectively. The maximum photoelectrochemical response of samples in K2SO3 (0.25M) and Na2S (0.35M) aqueous solution reaches 2.3mAcm−2 at an external potential of +1.0V vs. an Ag/AgCl reference electrode under illumination using a 300-W Xe lamp. The experimental results show that Ga doping with an [Ga]/[(Ga+In)] molar ratio of 0.02 improves the performance of the AgIn5S8 photoabsorber for photoelectrochemical applications.