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1.
《Journal of Non》2007,353(16-17):1676-1680
Spectroscopic properties of Tm3+ in (1 − x) (Ge0.25Ga0.10S0.65)–xBr (or CsBr) glasses (x = 0.0 and 0.1) were investigated. Emission properties of Tm3+ in 0.9(Ge0.25Ga0.10S0.65)–0.1Br glass were similar to those in Ge0.25Ga0.10S0.65 glass, while there was significant improvement when doped into 0.9(Ge0.25Ga0.10S0.65)–0.1CsBr glass. The lifetime of the Tm3+:3H4 level increased from 0.23 to 1.22 msec with 10 mol% CsBr addition. The presence of Cs+ facilitated the formation of [GaS3/2Br]− units by donating an electron to the Ga tetrahedron, resulting in the homogeneous distribution of Br. In this way, Tm3+ ions have their local environment made of Br only. When Br ions were added instead of CsBr, [GaS(4−x)/2Br]− units with x > 1 were formed and Tm3+ ions were surrounded by both S and Br, producing a high phonon environment. 相似文献
2.
《Journal of Non》2007,353(13-15):1358-1363
Local structures of rare-earth ions in Ge–Ga–S–CsBr glasses were investigated to understand the structural origin on the emission property enhancement. The frequency of the phonon vibration controlling the multiphonon relaxation was changed to 245 cm−1 due to the formation of Ga–Br bonds with CsBr addition to sulfide glasses. Formation of this new chemical bond was also confirmed from the phonon side band spectra of Eu3+ ions. Analyses of the EXASF spectra proved that Tm3+ ions were surrounded by approximately seven S ions in Ge0.25Ga0.10S0.65 glass but were coordinated by ∼6 Br ions in the glass with 10 mol% of CsBr. 相似文献
3.
Tae Hoon Lee 《Journal of Non》2008,354(27):3107-3112
The formation of structural units in Ge-Ga-S glass with CsBr addition and its effect on the optical band gap and several spectroscopic properties of Ho3+ were investigated. The optical band gap of the host glasses and the oscillator strengths of Ho3+ absorption decreased sharply when the ratio of CsBr/Ga became close to unity. These property changes were associated with the formation of structural units of [GaS3/2Br]− and they have a crucial effect on the changes of the local structure around Ho3+ ions. The local structure was not sensitive to the As or Br addition but was critically dependent on the concentration of CsBr. 相似文献
4.
Rajendra Kumar Singh 《Journal of Non》2008,354(27):3166-3170
Room temperature electron spin resonance (ESR) spectra and temperature dependent magnetic susceptibility measurements have been performed to investigate the effect of iron ions in 41CaO · (52 − x)SiO2 · 4P2O5 · xFe2O3 · 3Na2O (2 ? x ? 10 mol%) glasses. The ESR spectra of the glass exhibited the absorptions centered at g ≈ 2.1 and g ≈ 4.3. The variation of the intensity and linewidth of these absorption lines with composition has been interpreted in terms of variation in the concentration of the Fe2+ and Fe3+ in the glass and the interaction between the iron ions. The magnetic susceptibility data were used to obtain information on the relative concentration and interaction between the iron ions in the glass. 相似文献
5.
A high-energy X-ray diffraction study has been carried out on a series of 0.5Li2S + 0.5[(1 − x)GeS2 + xGeO2] glasses with x = 0.0, 0.1, 0.2, 0.4, 0.6 and 0.8. Structure factors were measured to wave vectors as high as 30 Å−1 resulting in atomic pair distribution functions with high real space resolution. The three dimensional atomic-scale structure of the glasses was modeled by reverse Monte Carlo simulations based on the diffraction data. Results from the simulations show that at the atomic-scale 0.5Li2S + 0.5[(1 − x)GeS2 + xGeO2] glasses may be viewed as an assembly of independent chains of (Li+-S)2GeS2/2 and (Li+-O)2GeO2/2 tetrahedra as repeat units, where the Li ions occupy the open space between the chains. The new structure data may help understand the reasons for the sharp maximum in the Li+ ion conductivity at x ∼ 0.2. 相似文献
6.
The structure of fluorochlorozirconate glass with composition Zr0.55Ba0.20La0.05Na0.20F2.95−xClx with 0 ? x ? 0.9, i.e., up to ∼30% chlorine anions, has been simulated using molecular dynamics methods applied to a unit cell comprising 790 ions. The structure comprises a network of (mainly) corner and edge-linked ZrF8−pClp, ZrF7−qClq and LaF7−rClr polyhedra with sodium, barium and additional chlorine ions occupying irregular positions in space between the polyhedra. For chlorine concentrations above about 15%, the number of chlorine ions occupying corner bridging positions increases markedly which is expected to reduce the glass temperature. For chlorine concentrations greater than about 20%, the spatial distribution of ions is not uniform and clustering into zirconium rich and sodium, barium and chlorine rich regions occurs. The possibility that this phenomenon may be a precursor to the observed precipitation of barium chloride crystals just above the glass temperature is discussed. 相似文献
7.
Glasses of the system: (70−x) TeO2 + 15B2O3 + 15P2O5 + xLi2O, where x = 5, 10, 15, 20, 25 and 30 mol% were prepared by melt quench technique. Dependencies of their glass transition temperatures (Tg) and infrared (IR) absorption spectra on composition were investigated. It is found that the gradual replacement of oxides, TeO2 by Li2O, decreases the glass transition temperature and increases the fragility of the glasses. Also, IR spectra revealed broad weak and strong absorption bands in the investigated range of wave numbers from 4000 to 400 cm−1. These bands were assigned to their corresponding bond modes of vibration with relation to the glass structure. 相似文献
8.
《Journal of Non》2007,353(13-15):1251-1254
The local structures around Tm3+ in Ge0.25Ga0.10S0.65 and 0.90 (Ge0.25Ga0.10S0.65) − 0.10CsBr glasses were investigated using Extended X-ray absorption fine structure (EXAFS) spectroscopy. In Ge0.25Ga0.10S0.65 glass, Tm3+ ions are surrounded by approximately seven S ions. Addition of 10 mol% CsBr resulted in significant changes in the EXAFS spectrum of Tm3+ ions due to the changes in the local structure surrounding Tm3+ ions. The first-nearest coordination shell around Tm3+ ion is predominantly composed of about six Br ions in 0.90 (Ge0.25Ga0.10S0.65) − 0.10CsBr glass. 相似文献
9.
Juliane Kaufmann 《Journal of Non》2009,355(9):531-1619
The thermodynamics of the redox equilibrium of Cu+/Cu2+ were determined by square-wave voltammetry in glass melts with the base mol% compositions x Na2O · (100 − x) SiO2 (x = 15, 20, 26 and 33) and (26 − x) Na2O · x CaO · 74 SiO2 (x = 0, 5, 10 and 15) doped with 1 mol% CuO in the temperature range from 850 to 1150 °C. All recorded voltammograms showed two maxima attributed to the reductions of Cu2+ to Cu+ and Cu+ to metallic copper. Both peaks are shifted to smaller potentials with decreasing temperature. With increasing melt basicity, the [Cu+]/[Cu2+]-ratio first increases, and remains constant for optical basicities >0.56. The effect of composition on the redox equilibrium is explained by the incorporation of both Cu+ and Cu2+ in octahedral coordination into the melt structure. 相似文献
10.
Fanqing Zeng Guozhong Ren Xiannian Qiu Qibin Yang Jingwu Chen 《Journal of Non》2008,354(29):3428-3432
The Er3+ doped transparent oxyfluoride glass ceramics were obtained by appropriate heat treatment of the precursor glasses with composition (mol%) 50SiO2-xPbF2-(50 − x)PbO-0.5ErF3. The microstructure and optical properties of the glasses and glass ceramics were determined by differential scanning calorimetry (DSC), X-ray diffraction (XRD), absorption spectra and luminescence spectra. The intensity of upconversion luminescence significantly increased in glass ceramics compared to that in precursor glass. The emission bands centered around 660 nm (4F9/2 → 4I15/2) and 410 nm (2H9/2 → 4I15/2) were simultaneously observed in glass ceramics but cannot be seen in the corresponding precursor glass. The influence of different PbF2 content on the microstructure and upconversion luminescence of the samples was analyzed in detail. The results indicated that with the increase of PbF2 content, the Ω2 was almost the same and the ratios of red to green upconversion luminescence decreased in glass ceramics. 相似文献
11.
Robert Carl 《Journal of Non》2007,353(3):244-249
Glasses with the compositions xNa2O · 10MgO · (90 − x)SiO2, 10Na2O · xMgO · (90 − x)SiO2, 5Na2O · 15MgO · xAl2O3 · (80 − x)SiO2, xNa2O · 10MgO · 10Al2O3 · (80 − x)SiO2, 10Na2O · 10MgO · xAl2O3 · (80 − x)SiO2, 10Na2O · 5MgO · 10Al2O3 · (80 − x)SiO2 were melted and studied using UV-vis-NIR spectroscopy in the wavenumber range from 5000 to 30 000 cm−1. At [Al2O3] > [Na2O], the UV-cut off is strongly shifted to smaller wavenumbers and the NIR peak at around 10 000 cm−1 attributed to Fe2+ in sixfold coordination gets narrower. Furthermore, the intensity of the NIR peak at 5500 cm−1 increases. This is explained by the incorporation of iron in the respective glass structures. 相似文献
12.
The influences of different alkali and alkali-earth oxide substitutions on the properties of lithium-iron-phosphate (LIP) glasses have been studied. Na2O, K2O, MgO, CaO and BaO were used to substitute Li2O to prepare LIP glasses with molar compositions of (20 − x)Li2O − xR2O(RO) − 30Fe2O3 − 50P2O5 (x = 2.4, 4, 5.6 and 7.2). The glass transition temperature (Tg) was determined by the differential thermal analysis technique. The density and chemical durability of the prepared glasses were measured based on the Archimedes principle and the weight losses after the glasses were boiled in water. The results show that Tg decreases with the initial substitutions, whereas the density and chemical durability increase. The diminution of the aggregation effect of Li+ ions on the glass structure due to the decrease in Li+ concentration, the larger molecule weights of the substitutes, the mixed-alkali and depressing effects as well the slower mobility of substitute ions mainly contribute to the initial changes in Tg, density and chemical durability of the LIP glasses, respectively. Further increasing the amounts of substitutes brings about increasing diminution of the aggregation effect of Li+ ions and breakage of the glass network on the one hand and increasing amounts of substitutes with larger molecule weights and ion radii on the other hand. Both aspects influence the glass properties oppositely and consequently non-monotonic variations in the properties of LIP glasses with the substitutions are observed. 相似文献
13.
Yong Seop Han 《Journal of Non》2003,321(3):210-216
1.48 μm emission properties and the cross-relaxation mechanism of Tm3+ ions in 0.7(Ge0.25As0.10S0.65) + 0.15GaS3/2 + 0.15CsBr glass were investigated. Both the relative intensity ratio of the 1.48 μm emission to 1.82 μm and the measured lifetime of the 3H4 level decreased with increasing Tm3+ concentration. When temperature decreased from room temperature to 20 K, lifetimes of the 3H4 level increased from 670 to 970 μs. At the same time, the critical distance for cross-relaxation decreased from 1.11 to 0.93 nm. These results indicate that cross-relaxation (3H4, 3H6 → 3F4, 3F4) became less effective as temperature decreased. Analysis of the temperature dependence of cross-relaxation rates showed that cross-relaxation in Tm3+ is a phonon-assisted energy transfer process. The major phonon contributing to the process is from the Ga-Br vibration in [GaS3/2Br]− units. 相似文献
14.
The local glass structure of tellurite glasses containing CuO with the nominal composition x(CuO) · (1−x)(TeO2), where x=0.10, 0.20, 0.30, 0.40, and 0.50, as well as the valence state of the copper ions have been investigated by X-ray photoelectron spectroscopy (XPS) and magnetization measurements. The Te 3d core level spectra for all glass samples show symmetrical peaks (Te 3d5/2 and Te 3d3/2) at essentially the same binding energies as measured for TeO2 indicating that the chemical environment of the Te atoms in the glasses does not vary significantly with the addition of CuO. The O 1s spectra, however, show slight asymmetry for all glass samples which results from two contributions, one from the presence of oxygen atoms in the Te-O-Te environment (bridging oxygen BO) and the other from oxygen atoms in an Te-O-Cu environment (non-bridging oxygen NBO). The ratio of NBO to total oxygen was found to increase with CuO content and to be in good agreement with calculated values for the TeO4 trigonal bipyramid structure. Moreover, the appearance of a satellite peak in the Cu 2p spectra provides definitive evidence for the presence of Cu2+ ions in these glass samples where the asymmetry and broadening of the Cu 2p3/2 and Cu 2p1/2 peaks are indicative of the presence of both Cu2+ and Cu+ ions. The relative concentration Cu2+ determined from XPS is in good qualitative agreement with the determinations of Cu2+ from magnetic susceptibility measurements on the same glass samples. Furthermore the susceptibility data follow a Curie-Weiss temperature-dependent behavior (χ=C/(T−θ)) with negative Curie temperatures indicating that the predominant magnetic interactions between the Cu2+-Cu2+ exchange pairs are antiferromagnetic in nature. 相似文献
15.
Heon Song Seon-Ho LeeEun-Su Jang Dong-Wook KimR. Navamathavan Jin Soo KimCheul-Ro Lee 《Journal of Crystal Growth》2009,311(19):4418-4422
InxGa1−xN quantum dots (QDs) were grown on GaN/sapphire (0 0 0 1) substrates by employing nitridation of nano-alloyed droplet (NNAD) method using metal-organic chemical vapor deposition (MOCVD). In+Ga alloy droplets were initially formed by flowing the precursors TMIn and TMGa. Density of the In+Ga alloy droplets was increased with increasing precursors flow rate; however, the droplet size was scarcely changed in the range of about 100–200 nm. Two cases of InxGa1−xN QDs growth were investigated by varying the nitridation time and the growth temperature. It was observed that the InxGa1−xN QDs size can be easily changed by controlling the nitridation process at the temperature between 680 and 700 °C for the time of 5–30 min. Self-assembled InxGa1−xN QDs were successfully grown by employing NNAD method. 相似文献
16.
The optical properties of Cr3+ ions in lithium metasilicate (Li2O · SiO2) transparent glass-ceramics were investigated. The main crystalline phase precipitated was the lithium metasilicate (Li2O · SiO2) crystal. The percent crystallinity and crystalline size were ranging 65-75% and 20-35 nm, respectively. The color changes drastically to deep pink from emerald green upon crystallization. New and strong absorption bands appeared and the absorption intensity increases by about 10 times that in glass. These new absorption bands are found to be derived from Cr3+ ions in octahedral sites in the lithium metasilicate crystal lattice. Cr3+ ions substitute for three Li+ ions and occupy the distorted octahedral site between single [SiO4]n chains of lithium metasilicate crystal. The ligand field parameters can be estimated: 10Dq = 13 088 cm−1, B = 453 cm−1, Dq/B = 2.89 and C = 2036 cm−1. The near-infrared luminescence centered at 1250 nm was not detected in the deep pink glass-ceramics unlike emerald green glass. 相似文献
17.
Yanmin Yang Baojiu Chen Cheng Wang Qingyu Meng Xiaoxia Zhao Weihua Di Xiaojun Wang Lihong Cheng Yong Peng 《Journal of Non》2008,354(31):3747-3751
Erbium-doped glasses with composition xGeO2-(80 − x)TeO2-10ZnO-10BaO were prepared by melt-quenching technique. The phonon sideband spectra and the optical absorption band edges for the host matrix were confirmed by means of the spectral measurements. Standard Judd-Ofelt calculations have been completed to these glasses. The dependence of up-conversion and infrared emission under 980 nm excitation on the glass composition was studied. The quantum efficiencies for the 4I13/2 → 4I15/2 transition of trivalent erbium in the glasses were estimated. 相似文献
18.
Structure study of multi-component borosilicate glasses from high-Q neutron diffraction measurement and RMC modeling 总被引:1,自引:0,他引:1
A neutron diffraction structure study has been performed on multi-component borosilicate glasses with compositions (65 − x)SiO2 · xB2O3 · 25Na2O · 5BaO · 5ZrO2, x = 5-15 mol%. The structure factor has been measured up to a rather high momentum transfer value of 30 Å−1, which made high r-space resolution available for real space analyses. Reverse Monte Carlo simulation was applied to calculate the partial atomic pair correlation functions, nearest neighbor atomic distances and coordination number distributions. The Si-O network consists of tetrahedral SiO4 units with characteristic first neighbor distances at rSi-O = 1.60 Å and rSi-Si = 3.0 Å. The boron environment contains two well-resolved B-O distances at 1.40 and 1.60 Å and both 3- and 4-fold coordinated B atoms are present. A chemically mixed network structure is proposed including [4]B-O-[4]Si and [3]B-O-[4]Si chain segments. The O-O and Na-O distributions suggest partial segregation of silicon and boron rich regions. The highly effective ability of Zr to stabilize glassy and hydrolytic properties of sodium-borosilicate materials is interpreted by the network-forming role of Zr ions. 相似文献
19.
Guonian Wang Shiqing Xu Shixun Dai Jianhu Yang Lili Hu Zhonghong Jiang 《Journal of Non》2004,336(2):102-106
A series of new glasses of 70TeO2-(20 − x) ZnO-xPbO − 5La2O3-2.5K2O-2.5Na2O (mol%) doped with Yb3+ is presented. Thermal stability, spectra and laser properties of Yb3+ ions have been measured. It found that 70TeO2-15PbO-5ZnO-5La2O3-2.5K2O-2.5Na2O composition glass had fine stability ((Tx−Tg)>190 °C), high-stimulated emission cross-section of 1.25 pm2 for the 2F5/2 → 2F7/2 transition and existed measured fluorescence lifetime of 0.94 ms and the broad fluorescence effective linewidth of 72 nm. Evaluated from the good potential laser parameters, this system glass is excellent for short pulse generation in diode pumped lasers, short pulse generation tunable lasers, high-peak power and high-average power lasers. 相似文献