Er~(3+)/Yb~(3+)共掺光波导激光玻璃的光谱特性研究

制备了以P2O5,Nb2O5,Na2O,Ga2O3为基质的Er3 ／Yb3 共掺铌磷酸盐玻璃样品,差热分析显示其转变温度高达560℃,表明PNNG玻璃具有较高的热稳定性和离子交换特性。应用Judd-Ofelt理论计算了PNNG玻璃中Er3 离子的自发跃迁几率、荧光分支比和辐射寿命等光谱参量。同时利用McCumber原理研究了PNNG玻璃在1.53μm处的受激发射截面和带宽,其值分别为σe(λ)=6.9×10-21cm2,△λ=55.7nm,结果表明重金属氧化物Nb2O5的加入提高了PNNG玻璃的折射率,从而提高了玻璃的发射截面和带宽,改善了光学特性。     

Er3+/Yb3+共掺光波导激光玻璃的光谱特性研究

制备了以P2O5,Nb2O5,Na2O,Ga2O3为基质的Er3+/Yb3+共掺铌磷酸盐玻璃样品,差热分析显示其转变温度高达560℃,表明PNNG玻璃具有较高的热稳定性和离子交换特性.应用Judd-Ofelt理论计算了PNNG玻璃中Er3+离子的自发跃迁几率、荧光分支比和辐射寿命等光谱参量.同时利用McCumber原理研究了PNNG玻璃在1.53 μm处的受激发射截面和带宽,其值分别为σe(λ)=6.9×10-21cm2,△λ=55.7nm,结果表明重金属氧化物Nb2O5的加入提高了PNNG玻璃的折射率,从而提高了玻璃的发射截面和带宽,改善了光学特性.     

Yb3+掺杂锌锗碲酸盐玻璃的热分析、光谱和激光性质

设计了组成为0．70TeO2-(0．20-x)ZnO-xGeO2—0．05La2O3-0．025K2O-0．025Na2O-0．01Yb2O3(摩尔分数x=0,0．05，0．10，0．15和0．20)的碲酸盐激光玻璃，测试了热学性质、吸收光谱、荧光光谱和荧光寿命。计算了Yb^3 离子的吸收截面、受激发射截面、荧光有效线宽等参数。结果表明，组成为0．70TeO2-0．20GeO2-0．05La2O3-0．025K2O-0．025Na2O的玻璃具有优于著名的碲锌钠(TZN)玻璃的热稳定性，高的受激发射截面(1．23pm^2)。长的荧光寿命(0．92ms)和宽的荧光有效线宽(77nm)。通过激光性能评价。最小抽运强度为0．98kW／cm^2，表明掺Yb^3 组份的碲酸盐玻璃是实现高能短脉冲可调谐激光器的理想增益介质。     

La2O3含量对Tm3+掺杂碲酸盐玻璃热稳定性及光学性能的影响

采用高温熔融法,制备了75TeO2-20ZnO-xLa2O3-0.8Tm2O3(x=0、5、10、15mol%)系列玻璃。探讨了La2O3含量对玻璃热稳定性的影响规律;计算了Tm3+在玻璃中的Judd-Ofelt(J-O)强度参数、自发辐射概率、荧光分支比及荧光辐射寿命;分别在473nm和808nm泵浦源下测量了玻璃的荧光光谱,计算了Tm3+在碲酸盐玻璃中的荧光有效线宽、峰值受激发射截面。研究发现,随着La2O3含量的增加,碲酸盐玻璃ΔT(ΔT=Tx-Tg,即初始析晶温度Tx与玻璃转变温度Tg之差)从123℃增加到180℃,玻璃热稳定性提高;La2O3的添加有利于提高Tm3+在1.46μm处的荧光性能;当La2O3含量为15mol%时,其FWHM和FWHM×σe值最大,分别为113.2nm和409.33×10-28cm3。     

掺Er3 铅卤碲酸盐玻璃的光谱特性研究

分别以TeO2-PbCl2、ZnO-Na2O和TeO2-ZnO-Na2O为基质制备了掺Er3+铅卤碲酸盐(EDTPb)玻璃和碲酸盐(EDT)玻璃.差热分析(DTA)结果表明,EDTPb玻璃具有更高的热稳定性.应用McCum-ber原理计算的结果表明4 mol%PbCl2的加入可使EDT玻璃在1.53 μm处的发射截面提高6.7%,其峰值达8.79×10-21cm2,而有效宽度从65.8 nm增加到72.3 nm,因此,PbCl2的加入明显改善了玻璃的发光特性.同时应用Judd-Ofelt理论对2种玻璃中Er3+的自发跃迁几率、荧光分支比和能级寿命等光谱特性进行了计算.     

掺铒TeO2-B2O3-Nb2O5-ZnO玻璃系统的光谱性质和热稳定性的研究

制备了碲酸盐玻璃样品70TeO2-(15-x)B2O3-xNb2O5-15ZnO-1wt%Er2O3(TBN,x=0,3,6,9,12,15 mol%).测试了玻璃样品的热稳定性和光谱性质.根据Judd-Ofelt理论计算了TBN玻璃中Er3 离子的强度参数(Ω2=(5.42～6.76)×10-20 cm2,Ω4=(1.37～1.73)×10-20cm2,Ω6=(0.70～0.94)×10-20 cm2),发现随着Nb2O5含量的增加,Ωt(t=2,4,6)先增加后减小.研究表明Er-O键共价性主要受基质玻璃中非桥氧数的影响,而阴阳离子间电负性的影响可以忽略.应用McCumber理论计算了Er3 离子的受激发射截面(σe=(0.77～0.91)×10-20 cm2)和Er3 离子4I13/2→4I15/2发射谱的半高宽度(FWHM=65～73 nm).比较了不同基质玻璃中Er3 离子的荧光半高宽和受激发射截面.结果表明TBN玻璃系统具有较好的带宽性能,是一种制备宽带光纤放大器的潜在基质材料.     

掺Er3+碲锌铋酸盐玻璃光谱特性研究

制备了掺铒碲锌铋酸盐玻璃样品84.5TeO2-(15-x)ZnO-xBi2O3-0.5mol% Er2O3(TZB x=0,2,4,6,8,10mol%).测试和分析了玻璃样品的吸收光谱、荧光光谱和4I13/2能级寿命等参数.根据McCumber理论,计算了Er3 受激发射截面(σpeake=(6.31～8.57)×10-21cm2)、并测量了Er3 荧光半高度(FWHM=65～70nm).结果表明:适量Bi2O3(～6mol%)的引入,能较好地改善玻璃样品FWHM,σpeake,4I13/2能级寿命和量子效率等光谱参数.     

Er3 /Yb3 共掺锗碲酸盐玻璃荧光特性及OH-的影响

制备了Er^3 ／Yb^3 共掺的70TeO2-5LiO2(25-x)B2O3-xGeO2(x=0，5，10，15，20％(mol))系列锗碲酸盐玻璃，测试了其荧光光谱、红外吸收谱以及Er^3 的I13/2能级寿命，并根据McCumber理论计算了E^3 能级中^4I13/2→^4I15/2跃迁的受激发射截面。讨论了OH对此系列玻璃荧光特性的影响。结果表明：此系列玻璃作为掺Er^3 光纤放大器(EDFA)的基质材料具有较好的带宽特性，随着GeO2含量的增加及B2O3含量的减少，Er^3 的荧光强度和^4I13/2能级寿命逐渐提高，OH^-的存在使得Er^3 的荧光强度降低，荧光寿命减小。     

热处理对掺Er3+碲酸盐玻璃近红外发光性能的影响

采用高温熔融冷却法和原位受控析晶法,制备了两 种Er³⁺掺杂碲酸盐玻璃及微晶玻璃。对比研究了其析晶 性能及近红外发光性能;计算了Er³⁺在玻璃与微晶玻璃中的J-O强度参数、自发辐射 概率、荧光分支比和 荧光辐射寿命;在980nm波长泵浦源下测量样品的荧光光谱,计算荧 光有效线宽、峰值受激发射截面。结果发现, 采用合理的析晶热处理制度,可以获得透明度高的Er³⁺掺杂碲酸盐微晶玻璃;析 晶热处理能够有效地提高 Er³⁺在近红外波段的发光效率和拓宽其有效发光带宽;Er³⁺掺杂85TeO₂- 10TiO₂-5La₂O₃(TTL)碲酸盐微晶玻璃较78TeO₂-17ZnF₂-5Bi₂O₃(TZBF)碲酸盐微晶玻璃在1.55μm波段增益性能更好,有望在光纤放 大器中得到应用。     

WO3对掺铒碲酸盐玻璃的光谱性质的影响

为了满足光通信技术发展对光放大器材料的带宽要求,采用固相法制备了掺铒碲钨酸盐玻璃,研究了其光谱性质和热稳定性。用Judd-Ofelt理论计算了光谱的强度参量,根据McCumber理论计算了受激发射截面,其最大受激发射截面为1.85×10-20cm2,荧光半峰全宽最大值为104nm;用差热法分析了玻璃的热稳定性,析晶温度和转变温度之差最大值为131℃。结果表明,掺铒碲钨酸盐玻璃是一种良好的宽带放大器材料。     

Resistance switching in amorphous and crystalline binary oxides grown by electron beam evaporation and atomic layer deposition

Resistance switching random access non-volatile memories (ReRAM) could represent the leading alternative to floating gate technology for post 32 nm technology nodes. Among the currently investigated materials for ReRAM, transition metal binary oxides, such as NiO, Cu_xO, ZrO_x, TiO₂, MgO, and Nb₂O₅ are receiving increasing interest as they offer high potential scalability, low-energy switching, thermal stability, and easy integration in CMOS fabrication. In this work we investigate the resistive switching properties of NiO and Nb₂O₅ films grown by electron beam and atomic layer deposition (ALD) as a function of growth technique and electrode materials. The polycrystalline NiO and amorphous Nb₂O₅ films are initially in the high resistance state and exhibit reproducible unipolar switching after an appropriate forming stage. Beside noble metal electrodes, particular focus is on n⁺-Si, W, and TiN materials which are compatible with CMOS device fabrication process.     

Interfacial Engineering of Bifunctional Niobium (V)-Based Heterostructure Nanosheet Toward High Efficiency Lean-Electrolyte Lithium–Sulfur Full Batteries

High-efficiency lithium–sulfur (Li–S) batteries depend on an advanced electrode structure that can attain high sulfur utilization at lean-electrolyte conditions and minimum amount of lithium. Herein, a twinborn holey Nb₄N₅–Nb₂O₅ heterostructure is designed as a dual-functional host for both redox–kinetics–accelerated sulfur cathode and dendrite-inhibited lithium anode simultaneously for long-cycling and lean-electrolyte Li–S full batteries. Benefiting from the accelerative polysulfides anchoring–diffusion–converting efficiency of Nb₄N₅–Nb₂O₅, polysulfide-shutting is significantly alleviated. Meanwhile, the lithiophilic nature of holey Nb₄N₅–Nb₂O₅ is applied as an ion-redistributor for homogeneous Li-ion deposition. Taking advantage of these merits, the Li–S full batteries present excellent electrochemical properties, including a minimum capacity decay rate of 0.025% per cycle, and a high areal capacity of 5.0 mAh cm⁻² at sulfur loading of 6.9 mg cm⁻², corresponding to negative to positive capacity ratio of 2.4:1 and electrolyte to sulfur ratio of 5.1 µL mg⁻¹. Therefore, this work paves a new avenue for boosting high-performances Li–S batteries toward practical applications.     

Binding Sulfur‐Doped Nb2O5 Hollow Nanospheres on Sulfur‐Doped Graphene Networks for Highly Reversible Sodium Storage

Orthorhombic Nb₂O₅ (T‐Nb₂O₅) has recently attracted great attention for its application as an anode for sodium ion batteries (NIBs) owing to its patulous framework and larger interplanar lattice spacing. Sulfur‐doped T‐Nb₂O₅ hollow nanospheres (diameter:180 nm) uniformly encapsulate into sulfur‐doped graphene networks (denoted: S‐Nb₂O₅ HNS@S‐rGO) using hard template method. The 3D ordered porous structure not only provides good electronic transportation path but also offers outstanding ionic conductive channels, leading to an improved sodium storage performance. In addition, the introduction of sulfur to graphene and Nb₂O₅ leads to oxygen vacancy and enhanced electronic conductivity. The sodium storage performance of S‐Nb₂O₅ HNS@S‐rGO is unprecedented. It delivers a reversible capacity 215 mAh g^?1 at 0.5 C over 100 cycles. In addition, it also possesses a great high‐rate capability, retaining a stable capacity of 100 mAh g^?1 at 20 C after 3000 cycles. This design demonstrates the potential applications of Nb₂O₅ as anode for high performance NIBs.     

Advantageous Functional Integration of Adsorption‐Intercalation‐Conversion Hybrid Mechanisms in 3D Flexible Nb2O5@Hard Carbon@MoS2@Soft Carbon Fiber Paper Anodes for Ultrafast and Super‐Stable Sodium Storage

Using synergetic effects of various sodium storage modes and materials to construct high power, high energy, and long cycling flexible sodium anode materials is significant and still challenging. Here, by advantageous functional integration of adsorption‐intercalation‐conversion sodium storage mechanisms, a 3D flexible fiber paper anode with the composition of Nb₂O₅@hard carbon@MoS₂@soft carbon is designed and prepared. Based on the synergetic effects, it exhibits higher specific capacity than pure Nb₂O₅, with more excellent rate performance (245, 201, 155, 133, and 97 mAh g^?1 at the current density of 0.2, 1, 5, 10, and 20 A g^?1, respectively) than pure MoS₂ as well as admirable long‐term cycling characteristics (≈82% capacity retention after 20 000 cycles at 5 A g^?1). Relevant kinetics mechanisms are expounded in detail. This work can be helpful for preparing other types of hybrid and flexible electrodes for energy storage systems.     

High‐Performance Sodium‐Ion Hybrid Supercapacitor Based on Nb2O5@Carbon Core–Shell Nanoparticles and Reduced Graphene Oxide Nanocomposites

Sodium‐ion hybrid supercapacitors (Na‐HSCs) have potential for mid‐ to large‐scale energy storage applications because of their high energy/power densities, long cycle life, and the low cost of sodium. However, one of the obstacles to developing Na‐HSCs is the imbalance of kinetics from different charge storage mechanisms between the sluggish faradaic anode and the rapid non‐faradaic capacitive cathode. Thus, to develop high‐power Na‐HSC anode materials, this paper presents the facile synthesis of nanocomposites comprising Nb₂O₅@Carbon core–shell nanoparticles (Nb₂O₅@C NPs) and reduced graphene oxide (rGO), and an analysis of their electrochemical performance with respect to various weight ratios of Nb₂O₅@C NPs to rGO (e.g., Nb₂O₅@C, Nb₂O₅@C/rGO‐70, ‐50, and ‐30). In a Na half‐cell configuration, the Nb₂O₅@C/rGO‐50 shows highly reversible capacity of ≈285 mA h g^?1 at 0.025 A g^?1 in the potential range of 0.01–3.0 V (vs Na/Na⁺). In addition, the Na‐HSC using the Nb₂O₅@C/rGO‐50 anode and activated carbon (MSP‐20) cathode delivers high energy/power densities (≈76 W h kg^?1 and ≈20 800 W kg^?1) with a stable cycle life in the potential range of 1.0–4.3 V. The energy and power densities of the Na‐HSC developed in this study are higher than those of similar Li‐ and Na‐HSCs previously reported.     

Highly Reversible Lithiation of Additive Free T-Nb2O5 for a Quarter of a Million Cycles

Fast energy storage via intercalation requires quick ionic diffusion and often results in pseudocapacitive behavior. The cycling stability of such energy storage materials remains understudied despite the relevance to lifetime cost. Orthorhombic niobium oxide (T-Nb₂O₅) is a rapid ion intercalation material with a theoretical capacity of 201.7 mAh g⁻¹ (Li₂Nb₂O₅) and good cycling stability due to the minimal unit cell strain during (de)intercalation. Prior reports of T-Nb₂O₅ cycling between 1.3–3.1 V versus Li/Li⁺ noted a 50% loss in capacity after 10 000 cycles. Here, cyclic voltammetry is used to identify the role of the voltage window, state of charge, and potentiostatic holds on the cycling stability of mesoporous T-Nb₂O₅ thin films. Films cycled between 1.2–3.0 V versus Li/Li⁺ without voltage holds (Li_1.1Nb₂O₅) exhibited extreme cycling stability with 90.8% capacity retention after 0.25 million cycles without detectable morphological/crystallographic changes. In contrast, the inclusion of 60 s voltage holds (Li_2.18Nb₂O₅) led to rapid capacity loss with 61.6% retention after 10 000 cycles with corresponding X-ray diffraction evidence of amorphization. Cycling with other limited voltage windows identifies that most crystallographic degradation occurs at higher extents of lithiation. These results reveal remarkable stability over limited conditions and suggest that T-Nb₂O₅ amorphization is associated with high extents of lithiation.     

Synthesis and characterization of the semiconductor Li0.93Cu0.07Nb3O8: Application to oxygen evolution under visible light

The semiconductor Li_0.93Cu_0.07Nb₃O₈ is prepared by soft chemistry in aqueous electrolyte via Cu²⁺ → Li⁺ exchange between copper nitrate and LiNb₃O₈. The substituted niobate crystallizes in an orthorhombic symmetry and the semiconducting and photo-electrochemical properties are investigated for the first time. The oxide exhibits a dark brown color and the UV–Visible spectroscopy gives an optical gap of 1.42 eV, due to the crystal field splitting of Cu²⁺ in octahedral site. The thermal variation of the conductivity shows that Nb: 4d-electrons are localized and the data are fitted by a small-polaron hopping model σ = σ_o exp {−0.053 eV/kT} with a carrier density thermally activated. The capacitance measurement done in ionic electrolyte (Na₂SO₄, 10⁻² M) indicates n type semiconductor with mixed valences Nb^5+/4+, due to the hetero-valent substitution Li⁺/Cu²⁺, with a flat band potential of 0.28 V_SCE and electrons density of 2.17×10¹⁷ cm⁻³. The Nyquist diagram shows mainly the bulk contribution with a diffusion process. The valence band (6.39 eV below vacuum) derives from O^2-: 2p orbital with a small admixture of Cu²⁺: 3d character while the conduction band is made up of Nb⁵⁺: 4d orbital. The material is successfully tested for the oxygen generation with an evolution rate of 87 µmol mn⁻¹ g⁻¹ under visible light (29 mW cm⁻²) and a quantum yield of 0.35%.     

A Universal Scheme for Patterning of Oxides via Thermal Nanoimprint Lithography

Direct patterning of oxides using thermal nanoimprint lithography is performed using either the sol‐gel or methacrylate route. The sol‐gel method results in resists with long shelf‐life, but with high surface energy and a considerable amount of solvent that affects the quality of imprinting. The methacrylate route, which is limited to certain oxides, produces polymerizable resists, leading to low surface energy, but suffers from the shorter shelf‐life of precursors. By combining the benignant elements from both these routes, a universal method of direct thermal nanoimprinting of oxides is demonstrated using precursors produced by reacting an alkoxide with a polymerizable chelating agent such as 2‐(methacryloyloxy)ethyl acetoacetate (MAEAA). MAEAA possesses β‐ketoester, which results in the formation of environmentally stable, chelated alkoxide with long shelf‐life, and methacrylate groups, which provide a reactive monomer pendant for in situ copolymerization with a cross‐linker during imprinting. Polymerization leads to trapping of cations, lowering of surface energy, strengthening of imprints, which enables easy and clean demolding over 1 cm × 2 cm patterned area with ≈100% yield. Heat‐treatment of imprints gives amorphous/crystalline oxide patterns. This alliance between two routes enables the successful imprinting of numerous oxides including Al₂O₃, Ga₂O₃, In₂O₃, Y₂O₃, B₂O₃, TiO₂, SnO₂, ZrO₂, GeO₂, HfO₂, Nb₂O₅, Ta₂O₅, V₂O₅, and WO₃.     

Nb2O5对铁基合金激光熔覆层裂纹敏感性的影响

在45#钢基底上进行了铁基合金和铁基合金加Nb2O5的激光熔覆对比实验.通过工艺参数和Nb2O5含量的优选,获得了成形良好、无裂纹、组织致密均匀的高质量铁基激光熔覆层.采用渗透法观察熔覆层表面裂纹,利用金相显微镜和扫描电镜观察熔覆层横断面的显微组织,使用X射线衍射仪对熔覆层进行物相分析,并测试了熔覆层的硬度.分析结果表明,G312+0.6%Nb2O5(质量分数)熔覆层组织为细小的先共晶析出的碳化物等强化相均匀分布在由γ(Fe,Ni)固溶体和多种金属间化合物组成的共晶体中,且生长方向不同.Nb2O5改善铁基熔覆层抗开裂能力的原因一方面是Nb占据晶界增强了晶界结合,另一方面,部分Nb2O5受C的还原作用生成NbC,先共晶析出,成为异质核,提高了凝固结晶过程中的形核率,使得熔覆层组织得以细化,且降低了熔体中的C浓度,减少了Cr(Fe)碳化物脆性相的体积分数,熔覆层韧性增强,裂纹敏感性降低.     

Low loss Nb2O5 films deposited by novel remote plasma sputtering

We report the deposition of Nb2O5 films on unheated BK-7 glass substrates using remote plasma sputtering system. The remote plasma geometry allows pseudo separation of plasma and target bias parameters, which offers complete deposition rate control. Using appropriate oxygen flow rates, high-density and low-loss Nb2O5 films are deposited with rates up to 0.49 nm/s. Lower deposition rates (~0.026 nm/s) can also be obtained by working at low target current and voltage and at low pressure. Nb2O5 films deposited at different rates have the refractive index of about 2.3 and the extinction coefficient as low as 6.9×10-5.