Optical Properties and Radiation Stability of Sio2·nH2O Powders Modified by ZrO2 Nanoparticles

Russian Physics Journal -     

Specific Features of the Local Structure and Transport Properties of ZrO2–Sc2O3–Y2O3 and ZrO2–Sc2O3–Yb2O3 Crystals

Optics and Spectroscopy - The specific features of the local structure of ZrO2–Sc2O3–Y2O3 and ZrO2–Sc2O3–Yb2O3 crystals are revealed by optical spectroscopy using the Eu3+...     

Surface Modification of ZrO2–3Y2O3 with Highintensity Pulsed N2+ Ion Beams

Russian Physics Journal -     

Synthesis of GaN Nanorods by Ammoniating Ga2O3/ZnO Films

Large quantities of CaN nanorods are successfully synthesized on Si（111） substrates by ammoniating the films of Ga2O3/ZnO at 950℃ in a quartz tube. The structure, morphology and optical properties of the as-prepared CaN nanorods are studied by x-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, and photoluminescence. The results show that the CaN nanorods have a hexagonal wurtzite structure with lengths of several micrometres and diameters from 80 nm to 300hm, which could supply an attractive potential to harmonically incorporate future GaN optoelectronic devices into Si-based large-scale integrated circuits. The growth mechanism is also briefly discussed.     

Y2O3稳定ZrO2薄膜的结构和光学特性

用电子束蒸发法制备出四种不同Y2O3含量的Y2O3稳定ZrO2（YSZ）薄膜,用X射线衍射和透射光谱测定薄膜的结构和光学性能.结果表明：随着Y2O3含量的增加,ZrO2薄膜从单斜相向高温相（四方相和立方相）转变,获得了结构稳定的YSZ薄膜;YSZ薄膜的晶粒尺寸都比ZrO2薄膜的大,但随着Y2O3加入量的增加,晶粒尺寸有减小的趋势,薄膜表面也趋向光滑平整.所有YSZ薄膜的透射谱线都与ZrO2薄膜相似,在可见光和红外光区都有较高的透过率.Y2O3的加入还可以改变薄膜的折射率,在一定范围内可得到所需的任意折射率.     

EXAFS research on Nd2O3 nanoparticles modified by AOT

The Nd2O3 nanoparticles which modified by AOT was prepared using micrioemulsion method in the system of water /xylene.L3 edge XAFS was used to determine the difference of the local structure arund Nd^3 ion and the electrical structure between the nanocystalline Nd2O3 and the coarse bulk microcrystalline Nd2O3.It was found that Nd-O distance increased with the form of nanocrystallite and the intensity of absorption edge also enhanced at the same time.     

Photoluminescence quenching in zinc oxide modified by Al2O3 and Al2O3 · CeO2 Nanopowders under proton irradiations

The photoluminescence spectra of initial ZnO powder and that modified by Al₂O₃, Al₂O₃ · CeO₂ nanopowders are investigated in the range 360–660 nm before and after 100-keV proton irradiation. It is found that the introduction of nanoparticles causes a decrease in the UV-band intensity and a change in the luminescence bands in the visual spectrum due to V _O ⁺ oxygen vacancies, O _int ^- interstitial oxygen, and V _Zn ^- zinc vacancies. Luminescence quenching in the UV and visible spectra occurs under the effect of protons. The decomposition of the spectra into elementary defects and analysis of changes in their integrated intensity during modification and irradiation of the powders are carried out.     

Characterization of the electrical properties of Y2O3-doped CeO2-rich CeO2–ZrO2 solid solutions

Electrical properties of Y₂O₃-doped CeO₂-rich ZrO₂–CeO₂ system were characterized with a view point of its point-defect structural scheme. Theoretical calculation of partial electronic and ionic conductivity from total conductivity was done to investigate the combined homovalent and aliovalent doping effect on the overall electrolytic property. According to our study, combined homovalent and aliovalent doping can be one of the key solutions to overcome the fatal disadvantage of limited electrolytic stability of doped ceria system by which properly enhances the ionic conductivity and suppresses the electronic conductivity all at once. Feasibility and limitation of Y₂O₃-doped CeO₂-rich ZrO₂–CeO₂ system as a potential alternative electrolyte material for low or intermediate temperature SOFC were discussed.     

Application of soluble salt-assisted route to synthesis of β-Ga2O3 nanopowders

In the past β-Ga₂O₃ nanopowders were usually prepared from gallium-based compounds via wet chemical processes. However, those wet chemical routes would lead not only to high cost, but also to the inevitable contamination of the targeted products from unexpected doping. In this work, the soluble salt-assisted route has been applied to prepare β-Ga₂O₃ nanopowders with a yield of 96.5 % through the direct oxidation of Ga–Na₂SO₄ mixture at 600 °C followed by water washing. Systematical characterizations including SEM, TEM, XRD, Raman, IR, XPS, BET, UV–Vis diffuse reflectance and PL spectrum were conducted. The as-prepared nanopowders were composed of mesoporous nanoparticles and nanosheets with monoclinic Ga₂O₃, and had a broad UV and blue emissions band from 350  to 550 nm. Furthermore their optical band gap was 4.68 eV, exhibiting a red shift of 0.22 eV in comparison with pure bulk matrix. The interesting results indicated a wide range of soluble salt-assisted route for promising industrial production of β-Ga₂O₃ nanopowders.     

Eu3+掺杂2ZnO·2.2B2O3·3H2O红色荧光粉的发光性能

采用水热法合成2ZnO.2.2B2O3·3H2O:Eu3+红色荧光粉.其形貌、结构和光学性能分别用扫描电镜、X射线衍射和荧光光谱进行表征.扫描电镜图片显示样品的尺寸分布在0.1～1 μm范围内.随着Eu3+掺杂浓度的升高,样品向无定形的玻璃态转变.当激发波长为253 nm(属于Eu3+ -O2 -电荷迁移带吸收)时,样...     

第2系列ZrO2(Y2O3)薄膜的慢正电子研究

用慢正电子技术研究了在溅射时不加偏压,衬底加热３００℃,纯Ａｒ气氛下制备的用Ｙ２Ｏ３稳定的ＺｒＯ２薄膜材料（简称ＹＳＺ薄膜）,发现了ＹＳＺ薄膜在不同深度处的缺陷分布情况,退火温度对ＹＳＺ薄缺陷影响,简要讨论了致密、优质ＹＳＺ薄的制备方法。     

Thermal stability and photoluminescence property of hexagonal MoO3·0.55H2O microrods

The metastable phase of well-faceted, hexagonal, prism-like molybdenum oxide hydrate (MoO₃·0.55H₂O) was successfully synthesized by evaporating molybdic acid solution prepared through cation membrane electrolysis of Na₂MoO₄·2H₂O aqueous solution. The obtained crystals were characterized by X-ray diffraction (XRD), thermogravimetric (TG), scanning electronic microscopy (SEM) and photoluminescence (PL) spectrophotometry. The as-prepared MoO₃·0.55H₂O rods were of 2–4 μm in width and 5–12 μm in length. The MoO₃·0.55H₂O microrods displayed photoluminescence properties at room temperature and were transformed into stable orthorhombic α-MoO₃ after air annealing at 380 °C. Moreover, the influence of temperature factor on the phase transformation process, morphology and photoluminescence properties of MoO₃·0.55H₂O was investigated in detail.     

Infrared absorption studies on the superionic conductor ZrO2−Y2O3 crystal

Infrared absorption spectra of (1−x)ZrO₂−xYO_1.5, which is one of the superionic conductors, have been studied using thin films evaporated on Si plates. From absorption spectra obtained at normal incidence and at oblique incidence it is shown that ZrO₂−Y₂O₃ crystals have well-defined TO and LO infrared active phonons, though they have many defects. From the analysis of the spectra, x-dependences of the force constant and the effective charge are obtained, and it is found that the concept of the virtual ion crystal model is very useful to understand the infrared properties of the superionic conductor ZrO₂−Y₂O₃ crystal.     

Infrared photoluminescence and Raman spectra in the Y2O3–ZrO2 system

In this work we present laser-excited infrared photoluminescence and Raman spectra of zirconia with different yttria content (2%–9.5% Y ₂O₃) in order to investigate the effect of dopant on their optical properties. All the Raman spectra were taken over the range 100–800 cm^?1, and the Ar⁺ laser-excited luminescence over the range 16,000–19,000 cm^?1 (absolute frequency). The results are discussed on the basis of defects related to anion vacancies and changes in the disorder degree induced mainly by yttria content in the samples.     

Electrical transport characteristics of ZnO–Bi2O3–B2O3 glasses

Optically clear glasses in the ZnO–Bi₂O₃–B₂O₃ (ZBBO) system were fabricated via the conventional melt-quenching technique. Dielectric constant and loss measurements carried out on ZBBO glasses unraveled nearly frequency (1 kHz–10 MHz)-independent dielectric characteristics associated with significantly low loss (D?=?0.004). However, weak temperature response was found with temperature coefficient of dielectric constant 18?±?4 ppm °C^?1 in the 35–250 °C temperature range. The conduction and relaxation phenomena were rationalized using universal AC conductivity power law and modulus formalism respectively. The activation energy for relaxation determined using imaginary parts of modulus peaks was 2.54 eV which was close to that of the DC conduction implying the involvement of similar energy barriers in both the processes. Stretched and power exponents were temperature dependent. The relaxation and conduction in these glasses were attributed to the hoping and migration of Bi³⁺ cations in their own and different local environment.     

Luminescence and absorption of Tb3+in mo·Al2O3·B2O3·Tb2O3 glasses

Quantum yields of the green Tb luminescence for 254 nm excitation of glass compositions in the system MO·Al₂O₃· B₂O₃·Tb₂O₃ (M = Mg, Ca, Sr, Ba and Zn) were studied in relation to absorption and excitation spectra. Yields as high as 80% were observed. The Tb 4f-5d absorption maximum ranges from 218 to 232 nm, always at a longer wavelength than the glass matrix absorption. The yield strongly depends on the spectral position of the 4f-5d absorption, due to competing impurity absorption at 254 nm.     

Solvent effect on the optimization of 1.54 μm emission in Er-doped Y2O3–Al2O3–SiO2 powders synthesized by a modified Pechini method

In order to find a new Er-doped host for near infrared (NIR) optical amplifiers, a study on the optimization of the erbium emission ions in the Y₂O₃–Al₂O₃–SiO₂ system was performed. (100 ? x) Y₃Al₅O₁₂ ? (x) SiO₂ powders (x varies from 0 to 70, in mol%) with a fixed Er₂O₃ concentration of 1.0 mol% were synthesized by a modified Pechini method and heat-treated at 900 and 1000 °C. The photoluminescence (PL) spectra at 1540 nm of the ⁴I_13/2 → ⁴I_15/2 transition of Er³⁺ ions and the up-conversion spectra at visible region (²H_11/2 + ⁴S_3/2 + ⁴F_9/2 → ⁴I_15/2) upon 980 nm excitation were evaluated. Different techniques, such as thermogravimetry (TG), differential scanning calorimetry (DSC), X-ray powder diffractometry (XRD) and Fourier transform infrared spectroscopy (FT-IR) were considered to evaluate crystallization and phase-evolution of the powders as a function of the silica content (x) and annealing temperature. The analyses were based on the comparison between two different solvents used in the preparation of the polymeric resins: ethanol and water. The optimal conditions for ethanol are quite different than the conditions for water used as solvent, confirming that the PL properties at the NIR region are highly sensitive to the changes in the host stoichiometry and processing conditions. The highest emission intensity at 1540 nm was observed for x = 30 for ethanol and x = 70 for water, treated at 900 and 1000 °C, respectively. This result could be attributed to the combination of low symmetry and good dispersion of the Er³⁺ions in these hosts.     

Formation and photoluminescence of Y2O3–H3BO3:Eu3+ powders by mechanical alloying

Y₂O₃–H₃BO₃:Eu³⁺ powders were synthesized by the mechanical alloying (MA) method, and their structural and photoluminescent characteristics were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), thermogravimetric/differential thermal analysis (TG/DTA), and luminescence spectrophotometer. The crystallite size of the powder mixture milling for 30 minutes (min) by the Willaimson–Hall method was approximately 58.8 nm with strain of 0.00141; overall, the internal strain increased with the milling time (t_m). The morphology of the powder mixture with t_m, as observed by SEM, divided into three different stages: agglomeration (0 < t_m ≤ 30 min), disintegration (30min < t_m ≤ 120 min), and homogenization (120min < t_m ≤ 300 min). The transition temperature and the weight reduction rate of the sample powders were 645.58 °C and 2.851%, respectively. Furthermore, the photoluminescence of the powder mixture excited to 240 nm by a zenon discharge lamp (20 kW) was detected near 592 nm(⁵D_o → ⁷F₁), 613 nm, 628  (⁵D_o → ⁷F₂), and 650 nm (⁵D_o → ⁷F₃).