β-Ga2O3:Dy3+ 纳米棒束的制备和光致发光性质

采用水热法及后续热处理制备了β-Ga2O3：Dy^3＋纳米棒束. 利用X射线粉末衍射（XRD）, 场发射电子扫描显微镜（FESEM）、发光光谱等测试手段对β-Ga2O3：Dy^3＋的物相、形貌、发光性质等进行了研究. FESEM等测试表明水热样品是由直径约100 nm, 长约2 μm的纳米棒组成的长径比约为3的羟基氧化镓（GaOOH）纳米棒束. 经过900 ℃高温热处理, 得到了形貌和尺寸基本保持不变的β-Ga2O3：Dy^3＋纳米棒束. 光致发光测试表明, Dy^3＋的发光由分别归属于4F9/2-6H15/2的蓝光（460～505 nm, 491 nm为最强峰）和4F9/2-6H13/2的黄光（570～600 nm, 580 nm为最强峰）组成. Β-Ga2O3基质可以有效地向Dy^3＋传递能量. 与固相法样品相比, 采用水热后续热处理方法制备的样品在分散性、形貌、能量传递和寿命方面明显优于固相法样品.     

Growth and nitridation of β-Ga2O3 thin films by Sol-Gel spin-coating epitaxy with post-annealing process

Journal of Sol-Gel Science and Technology - β-Ga2O3 thin films have been successfully prepared on (0001) sapphire substrate by simple and effective sol-gel spin-coating method with...     

ZrO2–Sc2O3 Solid Electrolytes Doped with Yb2O3 or Y2O3

Russian Journal of Electrochemistry - The effects of the Y2O3 and Yb2O3 co-doping impurities on the transport characteristics and stabilization of the cubic phase in solid solutions based on...     

Enhanced Photocatalytic Performance of rGO Modulated β-Ga2O3 for Wastewater Treatment

Rapid urbanization has inevitably raised challenges by indirectly adding industry waste to the environment. This problem becomes even more severe when contamination of consumable water is considered. As a leading sector in semiconductor-related research to face such challenges, gallium oxide and its derivatives have shown remarkable performance by exhibiting controlled, recyclable photocatalytic activities. This work demonstrates the enhancement of the photocatalytic performance of β-Ga₂O₃, which is related to the structural and morphological variation induced by rGO wrapping. Firstly, the Ga₂O₃ nanostructures are obtained by calcinating gallium oxide hydroxide (GaOOH), which is synthesized via a simple chemical route. On the other hand, rGO wrapped β-Ga₂O₃ is synthesized using in-situ hydrothermal treatment. In addition to traditional characterizations such as X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, etc., the photocatalytic performance of both pristine and composite systems is studied by time-dependent UV–Vis absorption spectrum for the degradation of different organic toxic pollutants. It is observed that the composite sample exhibited a larger effective surface area and enhanced optical absorption in the UV–Vis range as compared to the pristine gallium oxide sample. Under UV light irradiation, the rGO wrapped β-Ga₂O₃ nanobars can degrade rhodamine B dye entirely within 25 min and exhibit a higher photodegradation rate of 0.1598 min⁻¹ which became 3.5 times higher as compared to that of pure gallium oxide.     

Calcination-temperature-dependent gas-sensing properties of mesoporous α-Fe2O3 nanowires as ethanol sensors

The mesoporous α-Fe₂O₃ nanowires (NWs) were successfully synthesized by changing the calcination temperature from 550 to 750 °C (marked NWs-550, NWs-650 and NWs-750) via using SBA-15 silica as the hard templates with the nanocasting method. The characterization results indicated that the bandgap of the as-prepared samples hardly changed and the high BET surface areas changed a little with the calcination temperature from 550 to 750 °C. Mesoporous α-Fe₂O₃ NWs had been found to possess the remarkable gas-sensing performance to ethanol gas. The gas-sensing behavior indicated that α-Fe₂O₃ NWs-650 exhibited the higher response than that of α-Fe₂O₃ NWs-550 and α-Fe₂O₃ NWs-750. The calcination-temperature-dependent gas-sensing properties were mainly attributed to the competition of surface defects and body defects by the crystallization temperature. The lower calcination temperature could create more surface defects to improve the gas-sensing response, while the higher temperature would reduce the body defect and make the charge carriers transport easily. As the result, the suitable calcination temperature was desired to optimize the defects of nanostructures to improve the gas sensitivity.     

Structural,Thermal, and Electronic Properties of Two-Dimensional Gallium Oxide (β-Ga2O3) from First-Principles Design

Two-dimensional (2D) materials with exotic electronic, optical and mechanical properties have attracted tremendous attention in the last two decades, due to their potential applications in electronics, energy storage and conversion technologies. However, only a few dozen 2D materials have been successfully synthesized or exfoliated. Motivated by the recent discovery of 2D gallenene, we have explored new 2D allotropes of β-Ga₂O₃, an emerging wide-band gap transparent conductive oxide (TCO) with a wide range of semiconducting applications. All the possible 2D allotropes of β-Ga₂O₃ with high energetic stability have been predicted using particle swarm optimization, combined with density functional theory calculations. The structural and dynamical stability of the predicted 2D allotropes has been analyzed. Although β-Ga₂O₃ is not a van der Waals material, results predict that one or two allotropes of β-Ga₂O₃ are stable. In addition, the accurate band structures of these 2D semiconducting oxides have been calculated using both the GGA and LDA-1/2 approach. Remarkably, monolayer Ga₂O₃(100) has a larger indirect band gap of 4 eV, demonstrating a new avenue for the discovery of 2D β-Ga₂O₃ based nano-devices with enhanced electronic properties.     

Rational solution growth of α-FeOOH nanowires driven by screw dislocations and their conversion to α-Fe2O3 nanowires

We report the rational synthesis of α-FeOOH (goethite) nanowires following a dislocation-driven mechanism by utilizing a continuous-flow reactor and chemical equilibria to maintain constant low supersaturations. The existence of axial screw dislocations and the associated Eshelby twist in the nanowire product were confirmed using bright-/dark-field transmission electron microscopy imaging and twist contour analysis. The α-FeOOH nanowires can be readily converted into semiconducting single-crystal but porous α-Fe(2)O(3) (hematite) nanowires via topotactic transformation. Our results indicate that, with proper experimental design, many more useful materials can be grown in one-dimensional morphologies in aqueous solutions via the dislocation-driven mechanism.     

Mechanochemical synthesis of Na-β/β″-Al2O3

Na-β/β″-alumina powders were synthesized by a mechanochemical processing. The influences of mechanical activation in the phase composition and microstructure of the final powders were investigated. Fine Na-β/β″-alumina powders were obtained at a lower temperature than that of a conventional solid-state reaction processing. The mechanism of the mechanical activation was studied. It was found that mechanical activation greatly affected the calcining process and phase composition of the precursory powders.     

Ga2O3-La2O3-Yb2O3-Er2O3(HO2O3)体系光谱性质的研究

根据稀土离子能级的特点,对Ga2O3-La2O3-Yb2O3-Er2O3(HO2O3)体系的光谱性质进行了探讨,发现它们有二类发光性质:Stokes发光和反Stokes发光,研究了发光强度和发射波长与掺杂离子的依赖关系,观察到由能量的共振转移引起的荧光浓度猝灭现象,并取得了最大发光强度时的掺杂离子浓度和一些规律性结果.     

209Bi NQR in Mixed Oxides 2Bi2O3· B2O3, 3Bi2O3· 5B2O3, and Bi2O3· 3B2O3

It was earlier found from nuclear quadrupole resonance (NQR) measurements and computer modeling that -Bi₂O₃, Bi₃O₄Br and mixed oxides Bi₂O₃· 2Al₂O₃, Bi₂O₃· 2Ga₂O₃, Bi₂O₃· 3GeO₂, and 2Bi₂O₃· 3GeO₂exhibit local ordered magnetic fields from 30 to 200 G. It thus follows that these compounds are not diamagnets in a conventional sence of the word. With the aim of revealing previously unknown magnetic properties in bismuth(III) oxide-based Main Group element compounds, the mixed bismuth–boron oxides 2Bi₂O₃· B₂O₃, 3Bi₂O₃· 5B₂O₃, and Bi₂O₃· 3B₂O₃were prepared and studied using ²⁰⁹Bi NQR. The quadrupole interactions of the ²⁰⁹Bi nuclei and their electronic environment were studied, the crystallochemical features of the compounds were discussed, and the conformity of the ²⁰⁹Bi results to the X-ray structure data was verified. The preliminary tests in the field of a permanent magnet showed that the resonance intensities increase in external magnetic fields, indicating that a magnetism of unknown nature develops in the titled compounds. It was found reasonable to continue studies of the magnetic properties of these compounds using single-crystal ²⁰⁹Bi NQR in external magnetic fields.     

Eu3+-doped β-Ga2O3 nanophosphors: annealing effect, electronic structure and optical spectroscopy

A comprehensive survey of electronic structure and optical properties of rare-earth ions-doped semiconductor is of vital importance for their potential applications. In this work, Eu(3+)-doped β-Ga(2)O(3) nanocrystals were synthesized via a combustion method. The evolution of the optical properties of nanophosphors with increasing the annealing temperature was investigated in detail by means of excitation and emission spectra at room temperature and 10 K. Eu(3+) ions were proved to be incorporated into the crystal lattice of the β-Ga(2)O(3) phase after annealing the as-prepared nanoparticles at 1100 °C. It was observed that the substitution of Eu(3+) for Ga(3+) occurred at merely single site, in spite of two crystallographically nonequivalent sites of Ga(3+) in β-Ga(2)O(3). Spectroscopic evidence corroborated and clarified the local symmetry of C(s) for Eu(3+) at this single site. From the high-resolution excitation and emission spectra, 71 crystal-field levels of Eu(3+) in β-Ga(2)O(3) were identified and analyzed in terms of 19 freely varied free-ions and crystal-field parameters based on C(s) symmetry. The standard deviation of the final fitting is as low as 12.9 cm(-1), indicating an excellent agreement between experimental and calculated energy levels. The temperature-dependent luminescence dynamics of the (5)D(0) multiplet for Eu(3+) in β-Ga(2)O(3) phosphors has also been revealed for the first time from 10 to 300 K.     

New gallium germanates with tunnel structures: α-Ga4GeO8 and Ga4Ge3O12

The structure of several gallium germanates has been established or confirmed (Ga₄GeO₈ α and β forms, Ga₂GeO₅, Ga₄Ge₃O₁₂). Among them, α-Ga₄GeO₈ exhibits a new type of tunnel structure resulting from an intergrowth of GeO₂ rutile elements in the β-gallia network. Large hexagonal tunnels take place at the junction of both lattices. This compound is the first term of a series having as general formula Ga₄M_2n−1O_4n+4. Several other compounds M = Ge (n = 1, 2), Ti (n = 2, 3, 11 …), and Sn (n = 1) belong to the same family.     

Electrically Stimulated Band Alignment Transit in Black Phosphorus/ β-Ga2O3 Heterostructure Dual-band Photodetector

In recent decades, dual-band photodetectors have received widespread attention due to better target identification, which are considered as the development trend of next generation photodetectors. However, the traditional dual-band photodetectors based on heteroepitaxial growth, superlattice and multiple quantum well structures are limited by complex fabrication process and low integration. Herein, we report a UV/IR dual-band photodetector by integrating ultra-wide gap β-Ga₂O₃ and narrow-gap black phosphorous(BP) nanoflakes. A vertical van der Waals (vdW) heterostructure is formed between BP and β-Ga₂O₃ by mechanically exfoliated method integrated without the requirement of lattice match. The heterostructure devices show excellent rectification characteristics with high rectifying ratio of ca. 10⁶ and low reverse current around pA. Moreover, the device displays obvious photoresponse under UV and IR irradiations with responsivities of 0.87 and 2.15 mA/W, respectively. We also explore the band alignment transit within the heterostructure photodetector at different bias voltages. This work paves the way for fabricating novel dual-band photodetectors by utilizing 2D materials.     

A Ga2O·11Al2O3 nanonet prepared by interfacial reaction growth approach and its application in fabricating GaN nanowires

A Ga₂O·11Al₂O₃ nanonet was synthesized by using Ga₂O₃ powder as the precursor to generate Ga₂O vapor in H₂ atmosphere which further reacted with Al₂O₃ at 730 °C to form Ga₂O·11Al₂O₃ at the interfaces of a porous anodic aluminum oxide (AAO) template. The prepared Ga₂O·11Al₂O₃ nanonet then served as a Ga₂O-stablizing reservoir to fabricate single crystal GaN nanowires. The residual Ga₂O₃ powder at the surface of the produced Ga₂O·11Al₂O₃ nanonet and the metallic Ga or Ga₂O from the Ga₂O·11Al₂O₃ decomposition reacted with ammonia to yield GaN nanowires at 780 °C. The reaction mechanisms were investigated.     

La—β—Al2O3固体电解质研究

以Ａｌ２Ｏ３和Ｌａ２Ｏ３为原料，采用烧结法制备了Ｌａ－β－Ａｌ２Ｏ３固体电解质。在１０＾－３～１０＾５Ｈｚ频率范围内，于８００～１５００℃温度区间测定了电解质的阻抗谱，度计算得到电导率。用该固体电解质组装成只有镧的化学位差的电池，得到了稳定的电池电动势，计算了待测合金中镧的活度，由此说明该固体电解质呈现Ｌａ＾３＋离子导电性，有希望制成Ｌａ传感器。测定钢和铸铁液中溶解态镧的活度。也可用于高温固态合金     

α-Fe2O3 nanotubes with superior lithium storage capability

Polycrystalline α-Fe(2)O(3) nanotubes with thin walls have been synthesized by one-step template-engaged precipitation of Fe(OH)(x) followed by thermal annealing. In virtue of the unique structural features, these α-Fe(2)O(3) nanotubes exhibit superior lithium storage capabilities with exceptional high-rate capacity retention as a potential anode material for lithium-ion batteries.     

Metathesis of Butylene-2 and Ethylene to Propylene over 3.0Mo／（Hβ＋γ-Al2O3） Catalysts with Different γ-Al2O3 Contents

A series of 3. OMo/(Hβ γ-Al2O3) samples with γ-Al2O3 contents in the range of 0-100% (mass fraction) was studied by means of XRD, NH3-TPD, TPR and BET determinations for characterizing their structures. The Hβ zeolite structure in the 3.0Mo/Hβ sample can be effectively stabilized by adding some γ-Al2O3 to Hβ zeolite. γ-Al2O3 mainly favors the formation of polymolybdate or multilayered Mo oxide, while Hβ mainly forms the Al2(MoO4)3 species, as evaluated by the TPR technique. When used as the catalyst for the metathesis of butylene-2 and ethylene to propylene, there exists a close correlation between the specific surface area and stability of the catalyst. The specific surface area of the catalyst shows the maximum when (Hβ γ-Al2O3) contains 30%γ-Al2O3, which is in agreement with that of the time needed for the reaction stablization. In the case of maximum surface area, the rate of coke deposition is the minimum.