首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 46 毫秒
1.
Ag+/Na+ ion-exchanged aluminosilicate glasses with uniform concentration profiles were prepared, and their electrical conductivities were investigated as functions of the ion-exchange ratio and the initial glass compositions. In the case of the ion-exchanged glasses of x20Ag2O–(1−x)20Na2O–10Al2O3–70SiO2 in mol%, the conductivity, σ, and its activation energy, Eσ, showed a minimum and a maximum at the same ion-exchange ratio x=0.3, respectively, and the mixed mobile ion effect (MMIE) was observed. The fully ion-exchanged sample attained σ=3.5×10−5 S/cm at 200 °C, which was 1.5 orders of magnitude larger than that of initial glass. In the case of x25Ag2O–(1−x)25Na2O–25Al2O3–50SiO2, the mixed mobile ion effect was also observed at x=0.5. The maximum conductivity of 2×10−4 S/cm at 200 °C was obtained in the fully ion-exchanged glass sample.

The electric relaxation analysis was also conducted on both systems, and Kohlrausch–Williams–Watts (KWW) fractional exponent β was obtained as a function of x. The decrease of β was observed near x≈0.3 in the former system, while that of the later system was independent of the ion-exchange ratio. Based on the structural analysis results, the observed behaviors were investigated from the point of view of the occupation of Ag+ ions on the non-bridging oxygen-site (NBO-site) and the charge compensation-site (CC-site) of AlO4 tetrahedral unit.  相似文献   


2.
Nd2O3-doped 43Bi2O3xB2O3–(57−x)SiO2–1.0Nd2O3 (x=57, 47, 39, 28.5, 19.5, 10, 0 mol%) bismuth glasses were prepared by the conventional melt-quenching method, and the Nd3+: 4F3/24I13/2 fluorescence properties had been studied in an oxide system Bi2O3–B2O3–SiO2. The Judd–Ofelt analysis for Nd3+ ions in bismuth boron silicate glasses was also performed on the basis of absorption spectrum, and the transition probabilities, excited-state lifetimes, the fluorescence branching ratios, quantum efficiency and the stimulated emission cross-sections of 4F3/24I13/2 transition were calculated and discussed. The stimulated emission cross-sections of 1.3 μm were quite large due to a large refractive index of the host. Although the effective bandwidths decreased with increasing SiO2 content, quantum efficiencies and stimulated emission cross-sections enhanced largely with increasing SiO2 content.  相似文献   

3.
M. Sural  A. Ghosh   《Solid State Ionics》2000,130(3-4):259-266
The electric conductivity of ZnF2–AlF3–PbF2–LiF glasses has been studied in the frequency range 10 Hz–2 MHz and in the temperature range from 300 K to just below the glass transition temperature. The conductivity decreases with the increase in the LiF content in the composition, which results from the trapping of F ions by Li+ ions. Small values of the stretching exponent β are observed for the present glasses. The value of the decoupling index decreases with an increase in LiF content, consistent with the composition dependence of the conductivity.  相似文献   

4.
The intrinsic luminescence of glasses of the CaO–Ga2O3–GeO2 system has been investigated. High chemical purity and optical quality glasses, both undoped and doped with transition and rare-earth ions with different compositions, were obtained by high-temperature synthesis. The influences of the basic glass composition, impurities (Cr3+, Mn2+, Eu2+, Nd3+, Ho3+, Er3+, and Ce3+) and different kinds of excitation, on the intrinsic luminescence of the CaO–Ga2O3–GeO2 glasses were investigated. The nature and possible mechanisms of the intrinsic luminescence in glasses of this system are discussed. The proposed models of intrinsic luminescence are supported by electron spin resonance spectroscopy.  相似文献   

5.
A new lithium ionic conductor of the thio-LISICON (LIthium SuperIonic CONductor) family was found in the binary Li2S–P2S5 system; the new solid solution with the composition range 0.0≤x≤0.27 in Li3+5xP1−xS4 was synthesized at 700 °C and characterized by X-ray diffraction measurements. Its electrical and electrochemical properties were studied by ac impedance and cyclic voltammetry measurements, respectively. The solid solution member at x=0.065 in Li3+5xP1−xS4 showed the highest conductivity value of 1.5×10−4 S cm−1 at 27 °C with negligible electronic conductivity and the activation energy of 22 kJ mol−1 which is characteristic of high ionic conduction state. The extra lithium ions in Li3PS4 created by partial substitution of P5+ for Li+ led to the large increase in ionic conductivity. In the solid solution range examined, the minimum conductivity was obtained for the compositions, Li3PS4 (x=0.0 in Li3+5xP1−xS4) and Li4P0.8S4 (x=0.2 in Li3+5xP1−xS4); this conductivity behavior is similar to other thio-LISICON family with the general formula, LixM1−yMy′S4 (M=Si, Ge, and M′=P, Al, Zn, Ga, Sb). Conduction mechanism and the material design concepts are discussed based on the conduction behavior and the structure considerations.  相似文献   

6.
Diffusion of 22Na in ion-conducting xNa2O·(1−x)B2O3 glasses (x=0.2 and 0.3) was investigated under standard conditions and under high pressure employing the radiotracer sectioning method. A slight decrease of the diffusion coefficients with increasing time of diffusion annealing is observed and attributed to a structural relaxation of the glass network. The temperature dependence of diffusion was measured below and also in a small temperature range above the glass transition temperature (TG). Below TG the diffusion coefficients obey Arrhenius relations. Diffusion in the glass with x=0.3 is fast and associated with an activation enthalpy of 71 kJ mol−1. The diffusion coefficients of the glass with x=0.2 are significantly smaller with an activation enthalpy of 112 kJ mol−1. The activation volume ΔV of Na-diffusion in 0.3Na2O·0.7B2O3 was determined from high pressure diffusion studies at 623 K. A value of 0.52 molar volume of the glass matrix was obtained. According to our knowledge this is the first measurement of an activation volume of diffusion in ion-conducting glasses. The present results will be discussed and compared with dc conductivity data for borate glasses and diffusion results for other oxide glasses reported in the literature.  相似文献   

7.
The spectroscopic properties of Er3+/Yb3+ co-doped Bi2O3–B2O3–WO3 (BBW) glasses were analyzed and discussed. The effect of WO3 content on the absorption spectra, the Judd–Ofelt parameters Ωt (t=2, 4, 6), emission spectra and the lifetime of the 4I13/2 level and the quantum efficiency of Er3+:4I13/24I15/2 transition were also investigated. With the substitution of WO3 for B2O3, the measured lifetime of the 4I13/2 level and the quantum efficiency of Er3+:4I13/24I15/2 transition increase from 0.98 to 1.31 ms and from 38.2% to 49.2%, respectively. The effective width of emission band and the emission cross-section both decrease slightly. And the emission spectra is analyzed via the different curve (σeσa) of BBW glasses, the influence of OHis also discussed.  相似文献   

8.
The results of the femtosecond time-resolved optical Kerr at 820 nm in GeS2–In2S3 chalcogenide glasses indicate that the response time in GeS2–In2S3 glasses is subpicosecond, which is predominantly due to the distortion of the electron cloud. The value of χ(3) in 0.95GeS2–0.05In2S3 glass is also as large as 2.7 × 10−13 esu, and it reduces with the addition of In2S3, which may be ascribed to the microstructure evolution of GeS2–In2S3 glasses. It is deduced that the intrinsic [Ge(In)S4] tetrahedral structure units that possess the high hyperpolarizability may do great contribution to the enhancement of third-order optical nonlinearity while [S3Ge–GeS3] ethane-like molecular units make no considerable contribution to that in femtosecond time scale. These GeS2–In2S3 and GeS2–In2S3-based chalcogenide glasses would be expected to be the promising materials for all-optical switching devices.  相似文献   

9.
In this study, we will develop the influences of the excess x wt% (x=0, 1, 2, and 3) Bi2O3-doped and the different fabricating process on the sintering and dielectric characteristics of 0.95 (Na0.5Bi0.5)TiO3–0.05 BaTiO3 ferroelectric ceramics with the aid of SEM and X-ray diffraction patterns, and dielectric–temperature curves. The 0.95 (Na0.5Bi0.5)TiO3–0.05 BaTiO3+x wt% Bi2O3 ceramics are fabricated by two different processes. The first process is that (Na0.5Bi0.5)TiO3 composition is calcined at 850 °C and BaTiO3 composition is calcined at 1100 °C, then the calcined (Na0.5Bi0.5)TiO3 and BaTiO3 powders are mixed in according to 0.95 (Na0.5Bi0.5)TiO3–0.05 BaTiO3+x wt% Bi2O3 compositions. The second process is that the raw materials are mixed in accordance to the 0.95 (Na0.5Bi0.5)TiO3–0.05 BaTiO3+x wt% Bi2O3 compositions and then calcining at 900 °C. The sintering process is carried out in air for 2 h from 1120 to 1240 °C. After sintering, the effects of process parameters on the dielectric characteristics will be developed by the dielectric–temperature curves. Dielectric–temperature properties are also investigated at the temperatures of 30–350 °C and at the frequencies of 10 kHz–1 MHz.  相似文献   

10.
Glasses in the binary system xAg2P2O6 − (1 − x)Ag2Te2O5 have been prepared for 0 x 1. For each composition only one glass transition temperature is observed in the temperature range of 180–220 °C. All glasses appear homogeneous considering their optical and electrical properties. Nevertheless, in SEM observations, some glass compositions appear to be heterogeneous after decoration following short nitric acid etching. For each composition, conductivity data obtained in the temperature range of 25–200 °C using impedance techniques obey an Arrhenius relationship with a composition independent pre-exponential term. Variation of the conductivity activation energy with x induces correlative variations of isothermal conductivity curves leading to an increase of the ionic conductivity of about one order of magnitude compared with linearity at 25 °C. This behaviour is discussed with respect to the thermodynamic properties of the glassy solutions.  相似文献   

11.
Sundeep Kumar  K. J. Rao   《Solid State Ionics》2004,170(3-4):191-199
Glasses in the system Li2O–GeO2–P2O5 have been prepared using melt quenching route. Li+ ion transport has been investigated in these glasses using both d.c. and a.c. conductivity measurements. Arrhenius plots of d.c. conductivity exhibits two different slopes, which has been discussed in the light of cluster-tissue model. A.c. conductivity data has been fitted to single power law. Dielectric relaxation has been analyzed based on the behaviour of moduli. Good collapse on to master plots is observed for both a.c. conductivity and moduli. The behaviour of Edc, s and β are found to be consistent when conductivity mechanism is considered as involving NBO–BO switching as the first step, which is followed by Li+ ion migration.  相似文献   

12.
The effect of Bi2O3 on the glass transition temperature, electrical conductivity and structure of LiBO2 glass has been investigated. Tg vs. composition curve shows three different linear regions, while there is an overall decrease in Tg with the increase in Bi2O3 content. The slope of these three straight lines is in a decreasing order. These results are interpreted in terms of the increase in the number of non-bridging oxygen atoms, substitution of Bi-O bond in place of B-O bond and change in Li+ ion concentration. The conductivity vs. composition curve exhibits two maxima which are interpreted in terms of the structural modification effect of Bi2O3 on LiBO2 network and mixed-former effect, respectively. Results obtained from the XPS studies of the samples of composition x 0.005, have shown that the number of non-bridging oxygen atoms from B-O bond increases with the increase in Bi2O3 content. It has a maximum value at x = 0.003 where the conductivity has also exhibited a maximum value. Further increase of Bi2O3 content causes decrease in it. For higher Bi2O3 content (x * > 0.005), O 1s spectra of Bi2O3 has been separated out from that of Bi2O3. Bismuth ions have been substituted for boron ions as network former ions.  相似文献   

13.
Glass–ceramics for sealing solid oxide fuel cells (SOFCs) were developed by sintering and crystallization of the powdered glass seal. The non-isothermal sintering kinetics and crystallization kinetics were studied for four glasses in the system 50SiO2·(45−x)BaO·xRO·5Al2O3 (R=Ca, Mg, Zn and x=0, 15) (mol%). Hot-stage microscopy (HSM) and differential thermal analysis (DTA) measurements demonstrated that it is possible to first sinter and then crystallize these glasses obtaining glass–ceramic seals with thermal expansion coefficients in the range 9–12×10−6 K−1.

The non-isothermal sintering kinetics was analyzed by computer simulations using a previously reported model of sintering for polydispersed glass powders which takes into account the particle size distribution, surface energy and viscosity. Good agreement was found between the measured kinetics with HSM and the calculated kinetics for all glasses.  相似文献   


14.
The magnetic measurements performed on xFe2O3(1-x)[B2O3 · PbO] glasses show that for x 5 mol.% Fe2O3 the thermal variation of reciprocal susceptibility obeys a Curie behaviour. For higher iron content, at T 50 K, a nonlinear variation, typical for systems with random distribution of exchange interactions is observed. At greater temperatures than 50 K a Curie-Weiss behaviour is shown. The composition dependence of the Curie constants is analysed in correlation with the number of Fe3+ and Fe2+ ions as determined from Mössbauer effect measurements. A comparison with the data obtained in case of xFe2O3(1-x)[3B2O3 · PbO] glasses is made.  相似文献   

15.
We report optical studies of the new material – Cr3+-doped lithium–germanate glass, containing Li2Ge7O15 (LGO) nanocrystalline particles. While only broadband 4T24A2 fluorescence from the low-field octahedral Cr3+ sites was observed from Cr3+ ions in the glass, in LGO nanocrystals high-field Cr3+ centers emit 2E–4A2 (R–lines) fluorescence. The process of crystallization in the course of isothermal annealing of glasses was monitored spectroscopically and the nucleation of LGO crystallites was observed starting from the smallest clusters. Using the 2E–4A2 fluorescence spectra it is possible to detect the ferroelectric phase transition in LGO:Cr3+ nanocrystals, whose critical temperature was found to be similar to that of the bulk crystals. Long-lived spectral holes were burned in the inhomogeneously broadened R-lines of Cr3+ in LGO nanocrystals at low temperatures. The linear temperature dependence of hole widths shows that the homogeneous broadening of 4A22E transitions of Cr3+ in nanocrystals is due to interaction of Cr3+ electronic levels with the two-level systems (TLS) of the surrounding glass. The range of the Cr3+-TLS elastic dipole–dipole interaction is estimated.  相似文献   

16.
A series of apatite-type La–Ge–O ceramics were prepared and their cation-defect at the 4f+6h sites and oxide ion-defect at 2a site were investigated. In LaxGe6O12+1.5x ceramics of x=6–12, the higher conductivities were obtained in the region of apatite composition, Lax(GeO4)6O1.5x−12 (x=8–9.33), and the highest conductivity was achieved for La9(GeO4)6O1.5 (x=9), where the number of cation (La3+) occupying the 4f+6h sites is 9 and the number of oxide ion occupying the 2a site is 1.5. The ceramics with cation- and oxide ion-defects were La9−0.66xSrx(GeO4)6O1.5 (x=0–1), La9−1.33xZrx(GeO4)6O1.5 (x=0–1), La9−xSrx(GeO4)6O1.5−0.5x (x=0–3), La9−xZrx(GeO4)6O1.5+0.5x (x=0–1), Lax(GeO4)3x−21(AsO4)27−3xO1.5 (x=0–3), Lax(GeO4)33−3x(AlO4)3x−27O1.5 (x=0–3), La9(GeO4)6−x (AlO4)xO1.5−0.5x (x=0–3), La9(GeO4)6−x(AsO4)xO1.5+0.5x (x=0–1), La9.33−xSrx(GeO4)6O2−0.5x (x=0–1.2) and Lax(GeO4)4.5(AlO4)1.5O1.5x−12.75 (x=8.8–9.83), which were prepared by the partial substitution of La3+and GeO44−of the basic apatite La9(GeO4)6O1.5 with Sr2+ or Zr4+ and AlO45− or AsO43−. Such substitutions lowered the conductivity of La9(GeO4)6O1.5. These results were discussed by the electrostatic interaction between Sr2+, Zr4+, AlO45− or AsO43− and oxide ion as a conductive species.  相似文献   

17.
Ti substituted BiFe1−xTixO3+δ films have been prepared on indium–tin oxide (ITO)/glass substrates by the sol–gel process. The films with x=0.00–0.20 were prepared at an annealing temperature of 600 °C. X-ray diffraction patterns indicate that all films adopt R3m structure and the films with x=0 and 0.10 show pure perovskite phase. Cross-section scanning shows the thickness of the films is about 300 nm. Through 0.05 Ti substitution, the 2Pr increases to 8.30 μC/cm2 from 2.12 μC/cm2 of the un-substituted BiFeO3 film and show enhanced ferroelectricity at room temperature. The 2Pr values are 2.63 and 0.44 μC/cm2 for the films with x=0.01 and 0.2, respectively. Moreover, the films with x=0.05 and 0.10 show enhanced dielectric property since the permittivity increases near 150 at the same measuring frequency. Through the substitution of Ti, the leakage conduction is reduced for the films with x=0.05–0.20.  相似文献   

18.
The nonlinear refractive index, n2, of films based on the new glass system Sb2O3–Sb2S3 was measured at 1064 nm with laser pulses of 15 ps, using a single-beam nonlinear image technique in presence of a phase object. The films were prepared from bulk glasses by RF-sputtering. A large value of n2 = 3 × 10−15 m2/W, which is three orders of magnitude larger than for CS2, was determined. The result shows the strong potential of antimony–sulfide glass films for integrated nonlinear optics.  相似文献   

19.
Polycrystalline (1−x)Ta2O5xTiO2 thin films were formed on Si by metalorganic decomposition (MOD) and annealed at various temperatures. As-deposited films were in the amorphous state and were completely transformed to crystalline after annealing above 600 °C. During crystallization, a thin interfacial SiO2 layer was formed at the (1−x)Ta2O5xTiO2/Si interface. Thin films with 0.92Ta2O5–0.08TiO2 composition exhibited superior insulating properties. The measured dielectric constant and dissipation factor at 1 MHz were 9 and 0.015, respectively, for films annealed at 900 °C. The interface trap density was 2.5×1011 cm−2 eV−1, and flatband voltage was −0.38 V. A charge storage density of 22.8 fC/μm2 was obtained at an applied electric field of 3 MV/cm. The leakage current density was lower than 4×10−9 A/cm2 up to an applied electric field of 6 MV/cm.  相似文献   

20.
The LaGa1−xyCoxMgyO3−δ solid solutions with rhombohedrally-distorted perovskite structure were ascertained to form in the concentration range of 0≤y≤0.10 at x=0.60 and 0≤y≤0.20 at x=0.35–0.40. Increasing cobalt content results in increasing electrical conductivity and thermal expansion of the perovskites. Thermal expansion coefficients of the LaGa1−xyCoxMgyO3−δ ceramics were calculated from the dilatometric data to vary in the range of 12.4–19.8×10−6 K−1 at 300–1100 K. Doping La(Ga,Co)O3−δ solid solutions with magnesium leads to increasing oxygen nonstoichiometry, electronic and oxygen ionic conductivity. Oxygen permeation fluxes through LaGa1−xyCoxMgyO3−δ membranes were found to be limited by the bulk ionic conduction and to increase with magnesium concentration, being essentially independent of cobalt content.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号