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1.
《Solid State Sciences》2012,14(8):1233-1237
In order to reveal the effects of rare earth elements on the rheological behavior of silicate melt, the properties of viscosity and thermal expansion of soda-lime-silica glass doped with Gd2O3 and Y2O3 were investigated by the rotating crucible viscometer and dilatometry. The results show that, introduction of Gd2O3 and Y2O3 increases the coefficient of thermal expansion and decreases viscosity of soda-lime-silica glass. When the amount of Gd2O3 and Y2O3 increases from 0 to 1.00 mol%, the coefficient of thermal expansion of soda-lime-silica glass increases firstly from 7.67 to 7.79 and 8.05, and then decreases to 7.78 and 7.66 ( × 10−6 °C−1) respectively. In the case of melting temperature, its value decreases from 1830K to 1714 K, and then elevates to 1727 K as the content of Gd2O3 up to 1.00 mol%, however, as Y2O3 content increases from 0 to 1.00 mol% the melting temperature decreases monotonously from 1830K to 1737 K. The viscosity, melting temperature and coefficient of thermal expansion of soda-lime-silica glasses co-doped with Gd2O3 and Y2O3 are larger, comparing with glasses doped solely with Gd2O3 or Y2O3. The effect of co-doping with Gd2O3 and Y2O3 on thermal expansion and viscosity properties of soda-lime-silica glass, which is similar with the mixed-alkali effect in silicate glasses, is also observed.  相似文献   

2.
Thermal annealing of Sm+3 or Er+3 doped Na2O/K2O/BaF2/BaO/Al2O3/SiO2 glasses led to the precipitation of nanocrystalline BaF2. The mean crystallite sizes were in the range from 9 to 15 nm as shown by XRD line broadening. Whereas glasses without rare earth oxides showed crystallites homogenously dispersed in the amorphous matrix, those doped with 0.05 mol% ErF3 or SmF3 showed highly agglomerated crystals. The latter was due to droplet phase separation in the rare earth doped glasses as proved by transmission electron microscopy while in the undoped glasses phase separation did not occur. Furthermore, the size of the droplets depended on the BaO-concentration. Fluorescence emission spectra of a samarium doped sample showed higher intensities than in the glasses they were prepared from.  相似文献   

3.
Optical and structural properties of xPbO·2xBi2O3(1−3x)B2O3 glasses of different composition have been studied using UV-VIS and FTIR spectroscopic techniques. Effects of gamma radiations on glass network and structural units have been studied by irradiating glass samples with a 60Co radioisotope to the overall dose of 2.5 kGy. It is shown that irradiation causes compaction of the borate network by breaking the bonds between trigonal elements, which leads to a decrease in the optical band gap energy. Changes in the atomic structure before and after the irradiation are observed and explained.  相似文献   

4.
The extent of the glass forming region is described as a function of the composition and of the cooling speed. The shape of this region is explained from the previously described La2S3La2O3Ga2O3Ga2S3 phase diagram. Glasses are obtained after relatively slow cooling (5°/min), in a definite region of compositions, which coincides with a relatively large concentration of ternary invariants. The thermal properties (transition temperatures and crystallization temperatures) were measured by DTA. For a relatively large region of compositions, glasses return to the equilibrium conditions with intermediate formation of the La3.33Ga6S12O2 metastable crystalline phase. An approach to the structure of the glasses is made by comparison with the crystal structures of the numerous ternary and quaternary crystalline compounds observed in the system, and by the comparison of the Raman spectra. It appears that these gallium oxysulfide glasses have many structural analogies with germanium sulfide glasses.  相似文献   

5.
Lanthanum silicated apatites with nominal composition La9.33+x(SiO4)6O2+3x/2 (−0.2 < x < 0.27) have been successfully synthesized by solid state reaction using a new reagent La2O2CO3 and amorphous SiO2 precursors. The formation mechanism of La2O2CO3 reagent, which cannot be purchased, has been followed by in-situ temperature depend XRD of La2O3 under CO2 atmosphere. The stability of this reagent during the synthesis step allowed to limit the formation of secondary phase La2Si2O7 and made the weighting of the reagent easier. High purity powders could be synthesized at the temperature of 1400 °C. Dense pellets (more than 98.5%) were obtained by isostatic pressing of powders calcined at 1200 °C and then sintered at 1550 °C. Traces of La2SiO5 secondary phase present in synthesized powder disappeared after densification and pure oxyapatite materials were obtained for all the compositions. Electrical measurements confirmed that conductivity behaviors of the sintered pellets were dependent to the oxygen over-stoichiometry. Indeed, a relatively high conductivity of 1 × 10−2 S cm−1 was exhibited at 800 °C for the nominal composition La9.60(SiO4)6O2.405 with low activation energy around 0.79 eV. The ionic conductivity properties were comparable with that of the earlier obtained materials.  相似文献   

6.
Ferromagnetic glass–crystalline materials were produced by sintering of glasses from the systems Bi2O3B2O3MnO and crystalline phase La0.6Sr0.4MnO3. The appropriate preparation procedure was applied as follows: synthesis of the starting components, mixing, milling, pressing and sintering at selected temperatures. The steps of the technological scheme were controlled by X-ray diffraction and infrared spectroscopy. Small crystals with size in the order of 1–5 μm were detected by transmission electron microscopy observations [TEM] after heath treatment. The magnetic properties were studied by a vibrating sample magnetometer [VSM] and the Curie temperature was detected at 353 K. The presence of a narrow hysteresis loop proves the ferromagnetic properties of the materials.  相似文献   

7.
Spherical magnetic Mg-Fe-O nanoparticles were successfully prepared by the crystallization of glass in the system K2O/B2O3/MgO/P2O5/Fe2O3. The magnetic glass ceramics were prepared by melting the raw materials using the conventional melt quenching technique followed by a thermal treatment at temperatures in the range 560–700 °C for a time ranging from 2 to 8 h. The studies of the X-ray diffraction, electron microscopy and FTIR spectra confirmed the precipitation of finely dispersed spherical (Mg, Fe) based spinel nanoparticles with a minor quantity of hematite (α-Fe2O3) in the glass matrix. The average size of the magnetic nano crystals increases slightly with temperature and time from 9 to 15 nm as determined by the line broadening from the XRD patterns. XRD studies show that annealing the glass samples for long periods of time at temperature ≥604 °C results in an increase of the precipitated hematite concentration, dissolution of the spinel phase and the formation of magnesium di-borate phase (Mg2B2O5). For electron microscopy, the particles were extracted by two methods; (i) replica extraction technique and (ii) dissolution of the glass matrix by diluted acetic acid. An agglomeration of the nano crystals to larger particles (25–35 nm) was observed.  相似文献   

8.
The dc and ac electrical conductivity of barium tellurite borate glass doped with Nd2O3 in the composition 50 B2O3- (20-X) BaO- 20TeO2 10 LiF or Li2O where x = 0.5, 1, 1.5 and 2 Nd2O3 were measured in the temperature range 303–648 K and in the frequency range 0.1–100 kHz. The dc and ac conductivities values increase, whereas the activation energy of conductivities decreases with increasing Nd2O3 content in the glasses containing LiF and by the replacement of LiF by Li2O the conductivity was found to decrease with addition of Nd2O3. The electrical conduction has been observed to be due to small polaron hopping at high temperatures. The frequency dependence of the ac conductivity follows the power law σAC (ω) = A ωs. The frequency exponent (s) values (in the range 0.94 and 0.33) decreases with increasing temperature. The dielectric constant and dielectric loss increased with increasing temperature and decreased with increase in frequency for all glasses studied. In LiF glasses, it is observed that, the values of ?\ and tan δ are observed to increase with the addition of Nd2O3 whereas they decrease in the glasses containing Li2O. The electrical modulus formalism has been used for studying electrical relaxation behavior in studied glasses. It is for first time that the Nd2O3 doped barium tellurite borate glasses have been investigated for dc and ac conductivities and dielectric properties over a wide range of frequency and temperature.  相似文献   

9.
A new type of glass from the Na2O–MeO–Al2O3–SiO2–LaF3 system where MeO = MgO, CaO, BaO and SrO has been studied. The aim of the investigation was to determine, by means of thermal techniques (DTA and DSC), the influence of alkaline earth ions additions on its thermal stability and the ability of LaF3 phase to crystallization. The effect of LaF3 crystallization was analyzed in connection with glass composition expressed by the Al2O3/(MeO + Na2O + 3La2F6) ratio varying from 0.4 to 0.8 for the alkaline earth admixtures. The compositions of the glasses have been designed so as to make it possible to define the effect of the charge of the ion modifiers (Na+, Me2+, La3+) on the alumina position in the framework of the glass. Two series of glasses were obtained with a different F content. The formation of LaF3 depends directly on the strength of the network and can be control by the Al2O3/modifiers ratio as well as the content of fluorine ions. Generally, it can be stated that transparent glass-ceramic with nanocrystallization of LaF3 can be obtained for Al2O3/(Na2O + MeO + 3La2F6) ≤0.6 in the examined glasses. The more the ionicity of the alkaline earth ions the greater the tendency for the crystallization of Me2LaF7 and MeF2. In the glass structure the substitution of oxygen ions by F ions facilitated the crystallization of LaF3. Simultaneously, it influenced the thermal stability of the aluminosilicate network and induced the crystallization of appropriate silicates during the heat treatment.  相似文献   

10.
The effects of alumina and CaF2 content on the crystallization behavior, fluorine loss, phase separation mechanism and optical properties of oxyfluoride glass ceramics were investigated. Three series of glasses in which their SiO2/Al2O3 ratio was different such as 1.8, 2.18 and 2.5 were examined. Results showed that the adopted ratios played key role significantly in the mechanism of phase separation of the glass. It modified from spinodal decomposition to nucleation and growth by decreasing the mentioned ratio.UV spectroscopy showed that owing to the small size of precipitated CaF2 crystals, i.e. 20 nm, in the glass with a silicon oxide to alumina ratio of 2.18 and initial CaF2 amount of 35 mol%, it remained transparent after heat treatment at 740 °C.  相似文献   

11.
On the basis of the mineral banalsit (BaNa2Al4Si4O16) and the addition of small B2O3 concentrations, transparent glasses were prepared. Furthermore, in order to achieve nucleation, LiF and CaF2 were added. Hexacelsian was formed in bulk crystallized glass samples whereas, monocelsian, as well as small quantities of nepheline and banalsite were crystallized from sintered glass powder. The scanning electron micrographs of the sintered samples show high crystallinity and crystals with sizes from nano to micrometers. The SEM micrographs and the EDX microanalyses show that nano size rods of monocelsian surrounded by micrometer-sized hexagonal nepheline, banalsite or residual glassy phase occur. The coefficient of thermal expansion of the samples sintered at 1000 °C was higher (12.93–9.52 × 10−6 K−1) in hexacelsian containing samples than in monocelsian (2.24–7.35 × 10−6 K−1) containing ones. The samples also showed notably different densities of 2.6424 and 2.4718 g/cm3, respectively.  相似文献   

12.
In this paper T g values of calcium (sodium) silicate glasses containing added with oxides of trivalent elements are reported. The plots of T g as a function of composition or vs. the ionic field strength prove to be useful in discussing the role of the oxides in the glass structure. It is found that, at least in the studied composition range, Sc2O3, Y2O3, La2O3, and In2O3, behave as network modifier oxides. In the compositional ranges studied, the hypothesis based on them well agree with the expectations based on the known criteria reported in literature and on FTIR spectra. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

13.
Eu3+ ions activated La2Ti2O7 (La2Ti2O7:xEu3+) phosphors have been successfully synthesized by a fractional precipitation method from commercially available La2O3, Eu2O3, HNO3, Ti(SO4)2·9H2O and NH3·H2O as the starting materials. Detailed characterizations of the synthetic products were obtained by fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), differential thermal analysis, thermogravimetry and derivative thermogravimetry (DTA-TG-DTG), transmission electron microscopy (TEM), and photoluminescence (PL) spectroscopy. The results show that the precursor is composed of amorphous particles with quasi-spherical in shape and about 50 nm in size. Moreover, the precursor could be converted into pure La2Ti2O7 phase by calcining at 1000 °C for 2 h in air. The as-synthesized La2Ti2O7 particles are approximate polyhedron in shape and about 100–200 nm in size. PL spectroscopy of La2Ti2O7:xEu3+ phosphors reveals that the strongest emission peak is located at 616 nm under 275 nm ultraviolet (UV) light excitation, which corresponds to the 5D07F2 transition of Eu3+ ions. The quenching concentration of Eu3+ ions is 10.0 mol%, and its corresponding fluorescence lifetime was 1.82 ms according to the linear fitting result. Decay study reveals that the 5D07F2 transition of Eu3+ ions has a single exponential decay behavior.  相似文献   

14.
Oxyfluoride glass-ceramics based on the aluminosilicate glass-matrix with the nano-phase of fluoride is an interesting material for optoelectronics. A new glass from the SiO2–B2O3–Na2O–LaF3 system in which nanocrystallization of LaF3 could be obtained as well is presented. Thermal stability of glass and the crystalline phases formed upon heat treatment were determined by DTA/DSC and XRD methods, respectively. The effect of the glass composition on thermal stability was investigated by the SEM method. It has been found that the addition of LaF3 increases the tendency to decomposition of the borosilicate glass. In glasses with the ratio B2O3/(Na2O+3La2F6)<1 it is possible to obtain the immersed crystallization of LaF3 in transparent glassy matrix. The process is preceded by LaOF formation. Glasses with the composition B2O3/(Na2O+3La2F6)≥1 revealed the tendency to La(BSiO5) crystallization.  相似文献   

15.
Two new compounds, LaInS2O and La5In3S9O3 were synthesized in the La–In–S–O quaternary system. Both compounds crystallize in the orthorhombic system with lattice constants a=20.5421(6) Å, b=14.8490(4) Å, c=3.9829(1) Å for LaInS2O, and a=4.1018(1) Å, b=26.833(1) Å, c=16.023(1) Å for La5In3S9O3. The structure of La5In3S9O3 was solved from single-crystal X-ray data, in the space group Pbcm, with Z=4; it is built from three-atom-thick (100)NaCl layers interleaved with fluorite-type ribbons, and is closely related to the structures of the known lanthanum and indium compounds La10In6S17O6 and La4In5S13. Both compounds LaInS2O and La5In3S9O3 exhibit a yellow color; measurement of their optical gaps gave 2.73 and 2.60 eV, respectively.  相似文献   

16.
Characteristic temperatures, such as T g (glass transition), T x (crystallization temperature) and T l (liquidus temperature) of glasses from the V2O5-MoO3-Bi2O3 system were determined by means of differential thermal analysis (DTA). The higher content of MoO3 improved the thermal stability of the glasses as well as the glass forming ability. The non-isothermal crystallization was investigated and following energies of the crystal growth were obtained: glass #1 (80V2O5·20Bi2O3) E G=280 kJ mol-1, glass #2 (40V2O5·30MoO3·30Bi2O3) E G=422 kJ mol-1 and glass #3 (80MoO3·10V2O5·10Bi2O3) E G=305 kJ mol-1. The crystallization mechanism of glass #1 (n=3) is bulk, of glass #3 (n=1) is surface. Bulk and surface crystallization was supposed in glass #2. The presence of high content of a vanadium oxide acts as a nucleation agent and facilitates bulk crystallization. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

17.
In the ternary system La2O3-P2O5-Na2O the partial system La2O3-Na4La2P4O15-LaPO4 has been examined by the thermal, dilatometric X-ray and microscopic analyses and its phase diagram provided. The lanthanum oxyphosphate La3PO7 melts incongruently at the 1590°C temperature and crystallizes in a monoclinic systema=11.20 Å,b=11.94 Å,c=7.01 Å,=93.79 andV=936.97 Å3.
Zusammenfassung Mittels Thermo- und dilatometrischer Analyse, Röntgendiffraktionsuntersuchungen und Mikroskopie wurde das Teilsystem La2O3 - Na4La2P4O15 - LaPO4 des ternären Systemes La2O3 - P2O5 - Na2O untersucht und ein Phasendiagramm entwickelt. Lanthanoxyphosphat La3O7 schmilzt inkongruent bei 1590°C und kristalliert in einem monoklinen System mita=11.20 Ä,b=11.94 Ä,c=7.01 Å,=93.79 undV=936.97 Å3.


The author thanks Mrs. B. Lagódka for the technical assistance (thermogravimetric analyses). The thermal study was supported by grant CPBP.  相似文献   

18.
Sodium borosilicate glass, with the ratio R = [Na2O]/[B2O3] varied from 0.31 to 1, were studied by IR spectroscopy and Raman scattering techniques. The dependence of the structure of borosilicate glasses on their composition was studied also for the section with a constant value R = 1. The main borate and silicate groups in the system, and especially changes in the structure of glasses depending on the ratio R were identified.  相似文献   

19.
The effects on the thermal properties and bioactivity of the substitution of CaO by La2O3, Y2O3 and Al2O3 in a glass of composition CaO·SiO2 were studied and compared. The trivalent metal oxides were all effective in raising the glass transformation and softening temperatures when they replaced CaO in the glass of composition CaO·SiO2. The experimental results suggest that Al2O3 plays the role of a glass-former, while La2O3 and Y2O3 behave as glass-modifiers. The tendency to devitrify appears to be the lower, the farther the glass composition is from those of the crystalline phases, owing to the need for diffusion over longer distances, the greater the composition difference. The substitution with the trivalent metal oxides is detrimental to the bioactivity, which is preserved only in the event of very small degrees of substitution. The most negative role appears to be played by Al2O3. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

20.
The glass formation boundaries in the La2S3-Ga2S3-Sm2S3 system have been determined using physicochemical methods (DTA, thermogravimetry, powder X-ray diffraction, and microstructure examination). The thermal stability and IR spectra of newly synthesized phases have been studied. Glasses of composition (Ga2S3)0.60 (La2S3)0.20 (Sm2S3)0.20 at 865 K are stable in atmospheric oxygen. The IR spectra of binary and ternary glasses are practically identical. The IR bands associated with M-S vibrations in the glasses have higher intensities and appear at higher frequencies than the same bands in the spectra of the crystalline components, which is likely due to the strengthened covalence of the M-S bonds in the glasses.  相似文献   

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