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1.
Narottam P. Bansal Robert H. Doremus A.J. Bruce C.T. Moynihan 《Materials Research Bulletin》1984,19(5):577-590
The crystallization of a number of glasses of the fluorozirconate family has been studied using powder X-ray diffraction and differential scanning calorimetry, as a function of time and temperature of heating. The main crystalline phases were β-BaZrF6 and β-BaZr2F10. Stable and metastable transformations to the low temperature α phases were also investigated. The size of crystallites in fully devitrified glasses was calculated to be from line broadening of the X-ray diffraction peaks. 相似文献
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The electrical conductivities of glasses in the ZrF4-BaF2 and ZrF4-BaF2-BaCl2 systems have been measured as a function of temperature. The conductivies of binary fluorozirconate glasses had values comparable to those previously measured for ternary systems. The introduction of chlorine in the glass network markedly decreased the electrical conductivity and increased the activation energy for conduction. The decrease in conductivity could not be explained exclusively on the basis of zero mobility for the Cl atoms; it is proposed that these atoms effectively hinder the motion of the conducting fluorine ions. The activation energy for electrical conduction in fluorozirconate glasses was analysed via a modification of the Anderson and Stuart model for anionically conducting glasses, in which the electrostatic energy was found to predominate. In chlorofluorozirconate glasses, this term appears to be less predominant. 相似文献
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The glass forming region of the (ZrF4BaF2ThF4)EuF2 system has been studied. EuF2 was found to replace up to about 85% of the BaF2 in a glass with a composition .615 ZrF4, .32BaF2, .07ThF4. The glass transition temperature is seen to increase with the EuF2 concentration. The 4f7→ 4f65d1 transition of the Eu+2 ion in the glass matrix was studied by optical absorption and compared with data taken on crystalline compounds containing Eu+2 in different environments. It is concluded from these results that the Eu+2 ion - and also the Ba+2 ion - is coordinated by 12 fluorides in the glass. 相似文献
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A second characteristic ZrZr distance due to edge-sharing (ZrFn) polyhedra which is observed in crystalline α-ZrF4 (high temperature form) and is also suggested by recent X-ray studies of BaF2ZrF4 glasses, has been observed in ion dynamics computer simulation studies. Experimental X-ray and computer simulation results both imply that about one out of each four bridges between Zr pairs involve two fluoride ions, and that this proportion is almost independent of composition in the binary system. 相似文献
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Influence of processing conditions on IR edge absorption in fluorohafnate and fluorozirconate glasses 总被引:1,自引:0,他引:1
M.G. Drexhage C.T. Moynihan B. Bendow E. Gboji K.H. Chung M. Boulos 《Materials Research Bulletin》1981,16(8):943-947
The influence of processing conditions on the IR absorption edge of fluoride glasses with the composition 62 MF4 1b 33 BaF2 1b 5 LaF3 (M = Hf or Zr) is reported. At higher values of the absorption coefficient (α > 1 cm?1), the IR edge is nearly independent of processing conditions and appears to be intrinsic. At lower values (α < 1cm?1) extrinsic features attributed to oxide impurities appear; these are suppressed when glass melting is carried out in a reactive atmosphere of CCl4. Comparison of our results for HfF4- and ZrF4 based glasses shows that substitution of HfF4 for ZrF4 shifts the IR edge to longer wavelengths, but the intrinsic absorption curves are nearly parallel over the frequency range investigated. 相似文献
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L. Samek 《Journal of Materials Science》1995,30(22):5649-5651
The effect of nitrogen on the properties and structure of fluorozirconate glasses in the system ZrF4-BaF2-LaF3-AlF3 (ZBLA) was investigated. Nitrogen was introduced by means of aluminium nitride. The substitution of fluorine by nitrogen in ZBLA glasses resulted in a considerable increase of microhardness, reduction of the linear expansion coefficient, and a small increase in characteristic temperatures. Structural investigations comprised RDF and Fourier transform-infrared (FT-IR) examinations. From radial distribution function (RDF) it followed that the introduction of nitrogen caused an increase of the mean distances Zr-F(N), Ba-F(N), La-F(N). From FT-IR spectra, it followed that nitrogen became incorporated into the bridging fluorine atoms which was evinced by a shifting of bands deriving from the bending vibrations between the [ZrF6]2– octahedra towards higher wave numbers. 相似文献
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The corrosion of alkali-containing fluorozirconate glasses in water and acidic and alkaline solutions was studied with glasses of the compositions (100–x) (0.6ZrF4·0.1AlF3·0.3BaF2)· xLiF and 48ZrF4·8AlF3·24BaF2·xLiF·(20–x)NaF. The corrosion of the glasses in deionized water and 0.1 n HCl solution is mainly controlled by diffusion with an inductive period due to the passage from reaction-controlled to diffusion-controlled mechanisms, and the weight loss of glass increases with increasing LiF content in the single-alkali glasses. There was no appreciable effect of alkali mixing on the corrosion of glasses in deionized water and 0.1 n HCl solution. The glasses exhibited good stability in alkaline solution. The weight loss due to corrosion of the glasses in acidic buffered solution increased exponentially with increasing LiF content. 相似文献
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The effect of oxide dopant on the structure of 62ZrF4-30BaF2-8LaF3 (mol%) glass by equimolar substitution of BaO for BaF2 was studied by X-ray photoelectron spectroscopy (XPS). The XPS spectra of La 3d, Ba 3d, F 1s, O 1s and Zr 3d were measured. From the deconvoluted results for the XPS spectra of elements in the glass, it was proposed that the oxide ions added to the glass mainly bond to Zr4+ and replace the bridging fluoride ions resulting in the formation of the F-Zr-O bond. Further analyses indicated that the oxide ions mainly play a non-bridging role instead of a bridging role in the glass structure. 相似文献
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Measurements have been made on d.c. electrical conductivity of semiconducting lead tungsten phosphate glasses (X mol% WO3–(60–x) mol% PbO–40 mol% P2O5;x= 10, 20, 30, 40, 50 and 60) of six different compositions over a temperature range of 240 to 500 K. It is shown that the conduction can be described by a small polaron hopping model. When the WO3 content is 30 mol% the d.c. conductivity dc decreases and the activation energyW increases with increasing WO3 content and the glass samples exhibit predominant ionic conduction, however, when the WO3 content is > 30 mol%, dc increases andW decreases with the increase of tungsten ion concentration and the glass samples exhibit electronic conduction. The electronic conduction in these glasses havingx > 30 mol% seems to be adiabatic. Greaves variable range hopping has been found to be valid. The value of the electron wavefunction decay constant a is of the order of 16 nm–1. A minimum in the d.c. conductivity has been observed when the PbO concentration is 30 mol%. 相似文献
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Following recent measurements of very high d.c. conductivities in complex Li fluoride-borate-sulfate glasses, we have performed systematic measurements in the Li2OLiFB2O3 system. All glasses studied have essentially the same Arrhenius pre-exponential constant. Converting the data to conductivity relaxation times the pre-exponential constant corresponds to a frequency considerably higher than the Li+ - cage “rattling” frequency. Connections between the a.c. conductivity and the IR absorptivity are discussed. 相似文献
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A variation in d.c. conductivity and activation energy of 35 mol%CuO-65mol%P2O5 glasses is observed as CuO is gradually replaced by NiO or CoO. These results are believed to be due to the change in the
redox ratio of the two transition metal oxide glasses, which causes an increase and then a decrease of polaron hopping transitions
between the ions of the same element and between the ions of the different transition metal elements. 相似文献
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Oxyfluorophosphate glasses containing about 80 mol% of [LiF+Li2O] show unusually high lithium ion conductivity at elevated temperatures. A detailed investigation has been carried out on the glasses prepared by both conventional cooling and a rapid quenching technique. Chemical analysis of the glasses reveals fluorine loss during melting and it becomes difficult to make glasses with exact predetermined compositions. Electrical conductivity of the glasses, determined from complex impedance analysis increases with Li2O content. A glass with nominal composition 70 LiF15 Li2O15 Al(PO3)3 shows the highest conductivity (~ 1.3×10–3 ohm–1 cm–1 around 200° C) among all the compositions studied. An interesting feature of the impedance plot is the near perfect semicircle for bulk relaxation indicating a narrow distribution of relaxation times. This has been explained on the basis of a relatively small proportion of lithium ions which are mobile. The electrical conductivity of the glasses is found to be essentailly independent of dissolved water content. The infrared spectra of these glasses (2 to 50m region) could not produce much useful structural information. 相似文献
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Glasses of various compositions were prepared and included Pr6O11-CuO-P2O5 and Pr6O11-CaO-CuO-P2O5. The direct electrical conduction mechanism was generally discussed in terms of small polarons for the whole series of glasses.
Alternating electrical conduction was discussed according to the Elliott model and the Meyer-Neldel rule. 相似文献
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Measurements of d.c. electrical conductivity were made on 65TeO2-(35 -x)CuO-xLu2O3 (mol%) glasses with x=0, 1, 2, 3, 4. The experimental results show that whenx is changed from 1 to 2 mol%, the conductivity increases due to the additional electrons obtained by the oxidation of TeO2 as well as due to the Cu+ Cu2+ transition under the effect of interelectronic repulsion in the 4f shell of the lutetium present in the glass. Whenx is increased to greater than 2 mol%, the conductivity decreases because hopping is inhibited due to the formation of oxygen bridge associates or because of the strong ligand repulsive field of lutetium indicating its non-reactivity in the glassy network. The conductivity has a distinct maximum atx=2. 相似文献
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The electrical properties and internal friction in (40–x)Fe2O3·xNa20.60P2O5 glasses were measured. Two or three peak on internal friction were observed in the temperature range of –100 to 300° C at a frequency of about 1 Hz. The peak area of internal friction could be explained quantitatively by the additivity law of diffusion of Na+ ion and hopping of electrons which are carriers similar to those of dielectric loss. Activation energy, peak temperature of dielectric loss and internal friction showed almost the same value. Both relaxation phenomena have the same mechanism which is due to the diffusion of Na+ion and the hopping of electrons between Fe2+ Fe3+. The high-temperature peak is assumed to result from the interaction between protons or alkali ions and non-bridging oxygen. 相似文献