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1.
Enhanced luminescence in rare‐earth‐doped chalcogenide glass–ceramics is of great interest for the potential integrated optoelectronic devices. However, fundamental mechanism on the enhancement of luminescence upon crystallization remains largely unknown. We report the fabrication and characterization of wide transmission chalcogenide glass and glass–ceramics based on the 25GeS2·35Ga2S3·40CsCl:0.3Er glass composition, and discuss the mechanism of enhanced luminescence. By monitoring the 4I9/24I15/2 of Er3+ transition, up‐conversion luminescence of 12 times higher was observed in glass–ceramics compared with that in base glass. Electron paramagnetic resonance (EPR) and Raman scattering spectroscopies were employed to obtain the information of selective environment of Er3+ ions and microstructural evolution with the crystallization progress. Both of them evidenced that the enhanced up‐conversion luminescence was mainly related to the local environmental evolution from a mixed chlorine‐sulfur coordination to a low phonon energy chlorine coordination in the residual glassy matrix of glass–ceramics.  相似文献   

2.
Diagram of the phase transformation behavior of GeS2–Ga2S3–CsI glasses is realized in this article and the structure‐property dependence of the chalcogenide glasses is elucidated using differential scanning calorimetry and Raman spectroscopy. We observe the compositional threshold of crystallization behavior locates at = 6–7 mol% in (100?x)(0.8GeS2–0.2Ga2S3)–xCsI glasses, which is confirmed by the thermodynamic studies. Structural motifs are derived from the Raman result that [Ge(Ga)S4], [S2GeI2], [S3GaI], and [S3Ga–GaS3] were identified to exist in this glass network. Combined with the information of structural threshold, local arrangement of these structural motifs is proposed to explain all the experimental observations, which provides a new way to understand the correlation between crystallization behavior and network structure in chalcogenide glasses.  相似文献   

3.
Glass‐ceramics of PbS‐doped 80GeS2·20Ga2S3 were fabricated by heat treatments of base glasses at Tg+30°C for different durations. They exhibited improved mechanical properties such as hardness and resistance to crack propagation, and meanwhile retained their excellent infrared transmission. X‐ray diffraction and Raman results indicated that Ga2S3 and GeS2 crystals were precipitated inside glassy matrix. The crystallization kinetics of base glass was investigated using differential scanning calorimetry under nonisothermal conditions. Compared with the previous work concerning on 80GeS2·20Ga2S3 glass, there exists some different features of crystallization behavior. Such variation is discussed and correlated with the network structure and crystallization kinetics in this glass system.  相似文献   

4.
A series of (1 ? x)GeS2.5 – xSb chalcogenide glasses were prepared using the conventional melt‐quenching method. Their microstructure and thermal response were systematically studied. We observe a compositional threshold of x = 0.25 which corresponds to chemical stoichiometric composition in the calorimetric experiments. It is in good accordance with the Raman scattering results and laser‐induced phase transformation behavior. They also indicate that phase separation of Sb‐rich phase exists in the S‐poor samples. Moreover, we got a structural modeling of this phase separation: (1) at x = 0.25, which is chemical stoichiometric composition, the structural motifs are only SbS3 pyramid and GeS4 tetrahedra, and the three‐coordinated SbS3 pyramid is isolated by GeS4 tetrahedra; (2) at x < 0.25, the S–S bonds exist in the glass network due to the excess of S; and (3) at x > 0.25, the excess of Sb break the Ge–S and Sb–S bonds to form Sb(Ge)–Sb Bonds, and the Sb atoms segregate from the backbone to nucleate a separate Sb‐rich phase. This work provides a new way to investigate the phase separation of glass networks and helps us to better understand their related physical properties.  相似文献   

5.
熔融分相法是制备负载型纳米TiO2光催化材料的新方法。该方法是以Na2O-B2O3-SiO2-TiO2系为研究对象,通过制备不同组成的样品,并进行X射线分析及显微分析,进一步研究了熔融分相法中玻璃分相与TiO2析晶的关系。结果表明:组成在玻璃分相区域的样品,有玻璃分相现象产生,TiO2晶体能够析出,而在未分相区域的组成,样品中没有产生玻璃分相,TiO2晶体不能析出;玻璃分相的结构影响了TiO2晶体的生长,相同热处理条件下,组成中硅含量越少,其玻璃分相程度越大,TiO2析晶越容易,TiO2的析晶尺寸越大。  相似文献   

6.
7.
采用熔融-淬冷法制备了(100-x)(0.8GeS2-0.2Ga2S3)-xPbCl2(x=0,5,10,15,摩尔分数)系列硫卤玻璃,测试了样品的密度、可见-中远红外的透过性以及样品的折射率,并且根据Z扫描测试原理测试了飞秒脉冲下,样品在800 nm波长下的三阶非线性光学特性.结果表明:非线性折射率n2和非线性吸收系数β均随着PbCl2含量的增加而增大,特别是x=15的样品的非线性折射率n2=2.812×10-17m2/W,非线性吸收系数β=4.298×10-11m/W,较传统无重金属参杂硫系玻璃的三阶非线性性能明显提高.  相似文献   

8.
Hydration at 20°C of C11A7 · CaF2 which exists in regulated set cement was investigated by means of conduction calorimetry, differential thermal analysis, scanning electromicroscopic observation, X-ray diffraction and chemical analysis. The process of hydration and rate of hydration were determined and influence of the various calcium sulfates, calcium hydroxide and carboxylic acid upon the hydration of C11A7 · CaF2 was discussed. Mechanism of the strength development was also deduced in relation to the structure of hardened paste.  相似文献   

9.
K2O—CaO—Al2O3—SiO2系统玻璃的分相   总被引:2,自引:0,他引:2  
杜新民  沈定坤 《硅酸盐通报》1994,13(3):11-14,33
本文研究了K2O-Al2O3-SiO2玻璃的分相行为,从中发现该系统在液相线下的亚稳不混溶区能一直扩展到含SiO2量为53-60mol%的截面,K2O的引入能使该系统的不混溶温度升高,其分相的结构形貌的液滴状,滴状相是富硅相,含有SiO2,Al2O3和K2O,其尺寸大小服从对数正态分布。  相似文献   

10.
CaO-Al_2O_3-SiO_2玻璃表面上晶体生长动力学和分相影响杨晓晶,李家治(中国科学院上海硅酸盐研究所200050)许淑惠(西北轻工业学院712081)SurfaceCrystalGrowthKineticsinCaO-Al_2O_3-SiO...  相似文献   

11.
We prepared chemically stoichiometric, S‐poor and S‐rich Ge–Ga–S glasses and annealed them at a temperature that was 20°C higher than its respective glass transition temperature. We aimed at tuning the formation of the different crystals in chalcogenide glass‐ceramics. Through systematic characterization of the structure using X‐ray diffraction and Raman scattering spectra, we found that, GeS2 and GeS crystals only can be created in S‐rich and S‐poor glass‐ceramics, respectively, while all GeS, Ga2S3, and GeS2 crystals exist in chemically stoichiometric glass‐ceramics. Moreover, we demonstrated the homogeneous distribution of the crystals can be formed in the S‐rich glass‐ceramics from the surface to the interior via composition designing. The present approach blazes a new path to control the growth of the different crystals in chalcogenide glass‐ceramics.  相似文献   

12.
含氟CaO-Al_2O_3-SiO_2玻璃分相的研究   总被引:1,自引:0,他引:1  
在含硫化物的CaO-Al_2O_3-SiO_2(CAS)微晶玻璃系统中,氟作为有效的辅助晶核剂已得到了证明。虽然人们对含氟CAS微晶玻璃的晶化过程进行了较为详细的研究,但其分相以及分相与析晶的关系仍存在着许多值得探讨的问题。搞清楚氟对CAS玻璃分相的影响,无疑对进一步认识分相机理或开发CAS微晶玻璃新产品,都有着不可低估的意义。本  相似文献   

13.
In the present work, a large glass-forming region was found in the novel GeS2–Sb2S3–PbS system, in which up to 58 at.% PbS could be incorporated without deteriorating the thermal and physical properties of glasses. Infrared (IR) transmitting glass ceramics with a large amount of small-sized crystals (<100 nm) were then produced by choosing sub-stable compositions and annealing at fairly low temperatures (15°–30°C above T g) for long durations (up to 100 h). Crystals were identified by X-ray diffraction as Pb2GeS4, PbGeS3, PbS, PbSb2S4, etc., depending on base glass compositions. Compared with base glasses, glass ceramics showed much improved thermal shock resistance and fracture toughness, making them good candidate materials for IR optics.  相似文献   

14.
15.
Series of glassy and glass‐ceramic samples in the GeSe2–Ga2Se3–NaI system is prepared by melt‐quenching technique and the glass‐forming region is well‐defined by XRD investigations. Na‐ion conduction behavior is systemically studied by impedance measurements. For the glasses in the series (100?2x)GeSe2xGa2Se3xNaI, ionic conductivities increased with increasing x, whereas the attributed activation energy of ion conduction decreases. The enhanced mechanism is discussed by employing Raman spectra. In addition, the effect of the crystal phases NaI and Ga2Se3 on the ionic conduction behavior in the (70?x)GeSe2xGa2Se3–30NaI samples is discussed. Although it shows that the poorly conducting crystallites of NaI and Ga2Se3 have a negative effect on the ionic conductivities in this series, the highest ionic conductivity of 1.65 × 10?6 S/cm is obtained in the 45GeSe2–25Ga2Se3–30NaI glass. Finally, this study also demonstrates a possible way to search appropriate Na‐ion solid electrolytes for all‐solid‐state batteries.  相似文献   

16.
Friedels salt, the chlorinated compound 3CaO · Al2O3 · CaCl2 · 10H2O (AFm phase), presents a structural phase transition at about 30°C from a monoclinic to a rhombohedral phase. It has been studied by X-ray powder diffraction and optical microscopy in transmitted light with crossed polarisers on single crystals prepared by hydrothermal synthesis. The high temperature phase was determined at 37°C from X-ray single crystal diffraction data. The compound crystallises in the space group R c with lattice parameters of a = 5.7358(6)Å and c = 46.849(9)Å (Z = 3 and Dx = 2.111 g/cm3). The refinement of 498 independent reflections with I > 2σ(I) led to a residual factor of 7.1%. The Friedels salt can be described as a layered structure with positively charged main layers of composition [Ca2Al(OH)6]+ and negatively charged layers of composition [Cl,2H2O]. The chloride anions are surrounded by 10 hydrogen atoms, of which six belong to hydroxyl groups and four to water molecules. The structural phase transition may be related to the size of the chloride anions, which are not adapted to the octahedral cavity formed by bonded water molecules.  相似文献   

17.
A new compound of formula 2BaO·Al2O3·2H2O has been synthesised and studied by infra-red, X-ray and thermal analytical techniques. This hydrate yielded another crystalline product, 2BaO·Al2O3, during dehydration.  相似文献   

18.
A pronounced dielectric dispersion was observed along the a- and c-axes in a disordered nitrite compound of AgNO2·NH3. The activation energy of 0.32 eV was found for the dielectric relaxation time both along the a-axis and along the c-axis. Phase transition was not observed down to liquid helium temperature.  相似文献   

19.
Internally cooled, hollow SiC‐based ceramic matrix composites (CMCs) components that may replace metallic components in the hot section of future high‐efficiency gas‐turbine engines will require multilayered thermal/environmental barrier coatings (T/EBCs) for insulation and protection. In the T/EBC system, the thermally insulating outermost (top coat) ceramic layer must also provide resistance to attack by molten calcia‐magnesia‐aluminosilicate (CMAS) deposits. The interactions between a potential candidate for top coat made of air‐plasma‐sprayed (APS) 2ZrO2·Y2O3 solid‐solution (ss) ceramic and two different CMASs (sand and fly ash) are investigated at a relevant high temperature of 1500°C. APS 2ZrO2·Y2O3(ss) top coat was found to resist CMAS penetration at 1500°C for 24 hours via reaction products that block CMAS penetration pathways. In situ X‐ray diffraction (XRD) studies have identified the main reaction product to be an Ca‐Y‐Si apatite, and have helped elucidate the proposed mechanism for CMAS attack mitigation. Ex situ electron microscopy and analytical spectroscopy studies have identified the advantageous characteristics of the reaction products in helping the CMAS attack mitigation in the APS 2ZrO2·Y2O3(ss) coating at 1500°C. Finally, the Y3+ solubility limit and transport behavior are identified as potential comparative tools for assessing the CMAS resistance ability of top‐coat ceramics.  相似文献   

20.
The changes in the structure and phase composition of glasses in the MgO–Al2O3–SiO2–TiO2 system (at different TiO2 contents and ratios MgO : Al2O3) upon their heat treatment in the temperature range 700–960°C are investigated by small-angle X-ray scattering (SAXS) technique and X-ray powder diffraction analysis. The influence of gallium oxide additives on the phase separation and crystallization is analyzed. It is demonstrated that the heat treatment results in the phase separation, which occurs through the spinodal decomposition mechanism. A regular structure formed upon phase separation is retained after the completion of crystallization in inhomogeneity regions. The interference effects due to the regularity in the distribution of nanocrystals in the vitreous matrix bring about a decrease in the light scattering intensity and provide transparency of glass-ceramic materials.  相似文献   

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