Viscous How and MOS properties of CaF2-B2O3-GeO2-SiO2 glasses with ionic bonds

The capacitance and voltage (C-V) characteristics of Metal-Oxide-silicon (MOS) capacitors passivated by CaF₂B₂O₃-GeO₂-SiO₂ glasses with OH^– ions, water and fluoride contents were investigated. As the OH^– absorption coefficients of the glass increased, adverse effects on the recovery of hysteresis C-V curve shifts was observed. The content of OH^– ions is closely related to the fluoride content in the CaF2 B₂O₃-GeO₂-SiO₂ glass. The viscous-flow point of the glass was lowered with increasing degree of ionic character obtained from Hannay's equation.     

Ionic character of SrF2-B2O3-GeO2-SiO2 glasses for viscous flow and their applications to MOS capacitors

The capacitance and voltage (C-V) characteristics of metal, oxide, and semiconductors (MOS) capacitors passivated by SrF₂-B₂O₃-GeO₂-SiO₂ glasses with various water and fluoride contents were investigated. As the OH^– absorption coefficient of a glass increased, adverse effects on the recovery of shifts of the hysteresisC-V curve have been observed. The water content of ions is closely related to the fluoride content in the SrF₂-B₂O₃-GeO₂-SiO₂ glass. The viscous-flow transition point of glass was lowered with increasing degree of ionic character obtained from Hannay's equation.     

Application of BaF2-B2O3-GeO2-SiO2 glasses to metal-oxide-silicon field-effect transistors

The capacitance and voltage characteristics of field effect transistors passivated by BaF₂-B₂O₃-GeO₂-SiO₂ glasses with various water contents were investigated. As the OH absorption coefficients of the glass increased, adverse effects on the recovery of hysteresisC-V curve shifts was seen. The water content is related to the fluoride content of the BaF₂–B₂O₃–GeO₂–SiO₂ glass. The viscous flow point of the glass was lowered with increasing ionic character obtained from Hannay's equation. The source-drain current and voltage (I-V) characteristics of typical enhancement and depletion mode field effect transistors passivated with these glasses were investigated.     

Upconversion Luminescence of Er3+ Ions in Transparent Germanate Glass Ceramics Containing CaF2 Nanocrystals

The visible upconversion and near-infrared luminescence of Er3＋ ions in germanate glass ceramics containing GaF2 nanocrystals are investigated. The nanocrystals are characterized by x-ray diffraction （XRD） and transmission electron microscopy, showing their mean sizes less than 20hm. High transmittance of the glass ceramics is displayed by absorption spectra. The upconversion luminescence intensity in the glass ceramics increases significantly with increasing temperature. Both the shifts of the XRD peaks and the Stark-split shown in the luminescence spectra indicate the entrance of the Er3＋ ions into the CaF2 nanocrystals, which is confirmed by a Judd-Ofelt analysis. Possible mechanisms of the upconversion luminescence are analyzed.     

Ultrafast nonlinear optical properties of Bi2O3-B2O3-SiO2 oxide glass

The ultrafast nonlinear optical properties of Bi₂O₃-B₂O₃-SiO₂ oxide glass were investigated using a femtosecond optical Kerr shutter (OKS) at wavelength of 800 nm. The nonlinear response time of this Bi₂O₃-doped glass was measured to be <90 fs. The nonlinear refractive-index n₂ was estimated to be 1.6 × 10⁻¹⁴ cm²/W. Measurements for the dependence of Kerr signals on the polarization angle between the pump and probe beams showed that the Kerr signals induced by 30-fs pulse laser arose mainly from the photoinduced birefringence effect.     

Space-Selective Precipitation of Ba2TiSi2O8 Crystals in Sm3^＋-Doped BaO-TiO2-SiO2 Glass by Femtosecond Laser Irradiation

The ferroelectric crystal Ba2TiSi2O8 with high second-order optical nonlinearity is precipitated in Sm^3＋-doped BaO-TiO2-SiO2 glass by a focused 800hm, 250 kHz and 150fs femtosecond laser irradiation. No apparent blue and red emissions are observed at the beginning, while strong blue emission due to second harmonic generation and red emission due to the f-f transitions of Sm^3＋ are observed near the focal point of the laser beam after irradiation for 25s. Micro-Raman spectra confirm that Ba2 TiSi2O8 crystalline dots and lines are formed after laser irradiation. The mechanism of the phenomenon is discussed.     

Blue light emission from Eu ions in sol-gel-derived Al2O3-SiO2 glasses

Blue light-emitting glasses were successfully prepared by doping Eu²⁺ ions in the system Al₂O₃-SiO₂. The Al₂O₃-SiO₂ glasses doped with Eu³⁺ ions were synthesized using a sol-gel method, followed by heating in hydrogen gas atmosphere to reduce into the Eu²⁺ ions. The obtained glasses exhibited emission spectra with peak at ∼450 nm due to 4f⁶5d→4f⁷ (⁸S_7/2) transition, the intensities of which strongly changed depending on their glass composition and heating conditions. The emission quantum efficiency of 48% was achieved by heating the glass with the ratio of Al³⁺ to Eu³⁺ at about 6 at 1000 °C in hydrogen gas atmosphere. It was found that the Al₂O₃-SiO₂ glasses were appropriate not only for homogeneously doping the Eu³⁺ ions in glass structure but also reducing to Eu²⁺ ions, resulting in enhanced blue light-emission properties.     

Redox equilibrium of samarium ions doped in Al2O3-SiO2 glasses

Redox reaction of samarium ions doped in Al₂O₃-SiO₂ glasses, prepared by a rapid cooling technique of the melts, was examined by the measurement of the optical absorption and fluorescence properties. It was found that the doped samarium ions are easily reduced and oxidized by heating in H₂ and O₂ gases, respectively. The redox kinetics of samarium in the H₂ and O₂ atmospheres obey good first-order kinetics. The activation energy for the Sm³⁺ reduction in the 10Al₂O₃90SiO₂ glass was estimated to be ∼70 kJ/mol, which decreased with the increasing Al₂O₃ content. On the other hand, the activation energies for the oxidation were ∼90 kJ/mol, which only slightly depends on the glass composition. In these glasses, the samarium ions are preferentially surrounded by the Al-O polyhedra, where the oxygen ions are easily removed to form defect centers. It was concluded that the movement of the oxygen ions in the Al-O polyhedra determine the redox equilibrium of the samarium ions.     

Effect of hydroxyl groups on Er doped Bi2O3-B2O3-SiO2 glasses

A series of Er³⁺-doped Bi₂O₃-B₂O₃-SiO₂-Na₂O glasses with different hydroxyl groups were prepared and the interaction between the Er³⁺ ions and OH groups was investigated. Infrared spectra were measured in order to calculate the exact content of OH groups in samples. The observed increase of the fluorescence lifetime with the oxygen bubbling time has been related to the reduction in the OH content concentration evidenced by infrared (IR) absorption spectra, which confirmed that the OH groups were dominant quenching centers of excited Er³⁺ and a cause of concentration quenching of 1.5 μm band emission. Various nonradiative decay rates from ⁴I_13/2 of Er³⁺ with the change of OH content were determined from the fluorescence lifetimes and radiative decay rates, which were calculated on the basis of Judd-Ofelt theory.     

Quantum cutting downconversion by cooperative energy transfer from Bi3+ to Yb3+ in Y2O3 phosphor

Bi~(3+) and Yb~(3+) codoped cubic Y2O3 phosphors are prepared by pechini sol-gel method.Strong near-infrared (NIR) emission around 980 nm from Yb~(3+)(2F5/2 → 2F7/2) is observed under ultraviolet light excitation.A broad excitation band ranging from 320 to 360 nm,owing to the 6s 2 →6s6p transition of Bi~(3+) ions,is recorded when the Yb~(3+) emission is monitored,which suggests a very efficient energy transfer from Bi~(3+) ions to Yb~(3+) ions.The Yb~(3+) concentration dependences of both the Bi~(3+) and the Yb~(3+) emissions are investigated.The decay curve of Bi ~(3+) emission under the excitation of 355 nm pulse laser is used to explore the Bi~(3+) →Yb~(3+) energy transfer process.Cooperative energy transfer (CET) is discussed as a possible mechanism for the near-infrared emission.     

Cooperative Quantum Cutting of Nano-Crystalline BaF2：Tb^3＋, Yb^3＋ in Oxyfluoride Glass Ceramics

We report on cooperative quantum cutting in Tb^3＋- Yb^3＋ codoped glass ceramics. Precipitation of BaF2 nanocrystals is confirmed by XRD and HRTEM analysis. Near-infrared emission due to transition of Yb^3＋ ions under 485 nm excitation indicates cooperative energy transfer from Tb^3＋ to Yb^3＋. The quantum efficiency of this process reaches 145%. The realization of quantum cutting in glass ceramics may have promising applications in solar cells.     

Intense Green Upconversion Luminescence in Er^3＋：Yb^3＋ Codoped Fluorophosphate Glass Ceramic Containing SrTe5O11 Nanocrystals

Er^3＋ ：Yb^3＋ codoped tellurite-fluorophosphate （TFP） glass ceramic exhibits much stronger upconversion luminescence. The intensity of the 540nm green light and 651 nm red light of the TFP glass ceramic is 120 times and 44 times stronger than that of the fluorophospahte （FP） glass, respectively. XRD analysis shows that the nanocrystal in TFP glass ceramic is SrTe5O11. TFP glass ceramic also displays much higher upconversion fluorescence lifetime and crystallization stability. The narrow and strong peak at 540nm is very ideal for practical upconversion luminescence realization. This work is a new trial for exploring non-PbF2 involved nanocrystal upconversion glass ceramics.     

Sol-gel法制备Er3+-Yb3+共掺杂Al2O3粉末光致发光特性

采用异丙醇铝[Al(OC₃H₇)₃]为前驱体,溶胶-凝胶(Sol-gel)法制备Er³⁺-Yb³⁺共掺杂Al₂O₃粉末.实验结果表明:900 ℃烧结的粉末为固溶Er³⁺、Yb³⁺的γ-(Al,Er,Yb)₂O₃相和少量θ-(Al,Er,Yb)₂O₃相的混合物.Er³⁺-Yb³⁺共掺杂Al₂O₃粉末具有中心波长为1.533 μm的光致发光(PL)特性.1 mol % Er³⁺和1 mol% Yb³⁺共掺杂的Al₂O₃粉末的PL强度较1 mol % Er³⁺掺杂提高2倍,半峰宽从53 nm增加到63 nm.随泵浦功率的提高,PL强度呈线性增加后渐呈饱和趋势.     

Spectroscopic and magnetic studies of manganese ions in ZnO-Sb2O3-B2O3 glass system

ZnO-Sb₂O₃-B₂O₃ glasses containing different concentrations of MnO ranging from 0 to 1.0 mol% were prepared. A number of studies, viz. optical absorption, infrared and ESR spectra and magnetic susceptibility, were carried out as a function of manganese ion concentration. The analysis of the results indicate that manganese ions mostly exist in Mn²⁺ state in these glasses when the concentration of MnO≤0.6 mol% and above this concentration, these ions seem to exist in Mn³⁺ state in the glass network.     

Effect of hydroxyl groups on Er-doped bismuth-borate glass and fiber

A series of Er³⁺-doped Bi₂O₃-B₂O₃-GeO₂-Na₂O glasses with different OH⁻ group contents were prepared and the interactions between Er³⁺ ions and OH⁻ groups were investigated. The observed increase of the fluorescence intensity and decaying variation from an evident non-exponential to a nearly exponential behavior of the Er³⁺:⁴I_13/2 level with the oxygen gas bubbling time was related to the reduction of the OH⁻ group contents evidenced by infrared (IR) absorption spectra, which demonstrated that the OH⁻ groups were dominant quenching centers of the excited Er³⁺. Meanwhile, by reducing the OH⁻ group contents in the fiber cores with the same glass composition, the simulated gain characteristics improved dramatically and a 12.4 dB gain at 1560 nm was achieved in a 20 cm fiber with 150 mW pumping power at 980 nm.     

Intensities of f-f transitions in Pr3+ and Dy3+ in glasses in the near-IR spectral range

The absorption spectra of Pr³⁺ and Dy³⁺ ions in three glass matrices (SiO₂-P₂O₅-GeO₂, Al₂O₃-B₂O₃-SiO₂, and LiB₃O₅) are thoroughly studied in the near-IR spectral range (4600–14 300 cm^?1). The temperature dependences of the intensity, the width, and the location of the absorption bands observed are investigated for the first time. It is shown that the f-f transitions in the studied glasses are allowed by static odd distortions in the environment of the rare-earth ions and these distortions decrease with an increase in temperature. A comparative analysis of the absorption band parameters and their temperature behavior in different materials makes it possible to determine the differences in magnitudes, symmetries, and dispersions of the distortions in the nearest environment of rare-earth ions in different glasses.     

Study of molybdenum coordination state and crystallization behavior in MoO3-La2O3-B2O3 glasses by Raman spectroscopy

The ternary MoO₃-La₂O₃-B₂O₃ glasses containing a large amount of MoO₃ (10-50 mol%) are prepared, and their structure and crystallization behavior are examined from the Raman scattering spectrum measurements and X-ray diffraction analyses. It is found that the glass transition and crystallization temperatures and the thermal stability against crystallization decrease with increasing MoO₃ content. It is suggested that the main coordination state of Mo⁶⁺ ions in the glasses is isolated (MoO₄)²⁻ tetrahedral units giving strong Raman bands at 830-860 and 930 cm⁻¹. It is found that the crystalline phases in the crystallized glasses are mainly LaMoBO₆ and LaB₃O₆, and the main crystallization mechanism in MoO₃-La₂O₃-B₂O₃ glasses is surface crystallization. LaMoBO₆ crystals are found to give strong Raman bands at 810-830 and ∼910 cm⁻¹.     

Effect of CaO-B2O3-SiO2 glass on the magnetic and dielectric properties of NiCuZn ferrites

NiCuZn ferrites with different contents of CaO-B₂O₃-SiO₂ glasses were synthesized by a conventional ceramic technology and sintered at 1050 °C. It was found that the addition of CaO-B₂O₃-SiO₂ influenced the magnetic and dielectric properties of the ferrites. The saturation magnetization increased at first and reached its maximum with the sample of 2 wt% CaO-B₂O₃-SiO₂, and then decreased. The initial permeability decreased with the content of CaO-B₂O₃-SiO₂ but the cut-off frequency increased. The quality factor decreased first and then increased; the maximum quality factor was obtained in the sample with 3 wt% CaO-B₂O₃-SiO₂. With increasing content of CaO-B₂O₃-SiO₂, the permittivity increased sharply. The possible reasons responsible for these changes are explained.     

Thermoluminescent properties of a Li2O-B2O3-Al2O3 glass system doped with CaF2 and Mn

A Li₂O-B₂O₃-Al₂O₃ glass system doped with CaF₂ and Mn was synthesized by fusion and its physical properties were investigated using thermoluminescence (TL) and differential thermal analysis (DTA) techniques. The TL glow curve peaks, resulting from this analysis, are characteristic of metastable levels intrinsic to CaF₂ crystals that have undergone γ-ray irradiation from a colbalt-60 (⁶⁰Co) source. This provides evidence of CaF₂ crystal formation in the glass system. Furthermore, the TL glow peak at about 480 K was stable at room temperature, sensitive to ⁶⁰Co γ-rays and showed good linearity with doses ranging from 3 Gy to approximately 100 Gy, and consequently could be used to quantify radiation doses. High quality synthesis of these crystals permits control of their thermoluminescent properties.     

Relativistic Energies and Auger Widths of High-Lying Doubly-Excited States 1s^23lnl′ ^1De in Be-Like O^4＋ Ions

The saddle-point variational method and restricted variational method are used to calculate energies of doublyexcited singlet states 1s^23lnl′ （n =3-.） ^1 De in Be-like O^4＋ ions, including the mass polarization and relativistic corrections. The saddle-point complex-rotation method is used to compute the Auger widths and Auger transition rates. These results are compared with other theoretical and experimental data in the literature.