共查询到20条相似文献,搜索用时 15 毫秒
1.
S.S. Das 《Materials Research Bulletin》2008,43(11):3008-3016
Ag2O-P2O5 and Ag2O-P2O5-20 wt% CdCl2 glasses were prepared by melt quenching method and characterized with the help of several experimental techniques. Powder X-ray diffraction study indicated that the glasses are amorphous in nature. DSC studies showed that CdCl2 doped glass is chemically more durable. Electrical conductivity and ionic transference number measurements have shown that both the glasses are ionic conductors with Ag+ ions as the charge carriers. The electrical conductivity of the doped glass is found to be higher than the undoped one. Structures of the glasses have been proposed on the basis of IR spectral analysis. From SEM studies it has been inferred that addition of 20 wt% CdCl2 modifies the morphology of Ag2O-P2O5 glass and in its presence formation of clusters composed of nanofibers occur. 相似文献
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3.
Sherin Thomas 《Materials Research Bulletin》2008,43(4):843-851
The 0.83ZnAl2O4-0.17TiO2 (ZAT) ceramics were synthesized by solid state ceramic route. The effect of 27B2O3-35Bi2O3-6SiO2-32ZnO (BBSZ) glass on the microwave dielectric properties of ZAT was investigated. The crystal structure and the microstructure of the ceramic-glass composites were studied by X-ray diffraction and scanning electron microscopic techniques. The low frequency dielectric loss was measured at 1 MHz. The dielectric properties of the sintered samples were measured in the microwave frequency range by the resonance method. Addition of 0.2 wt% of BBSZ improved the dielectric properties with quality factor (Qu × f) > 120,000 GHz, temperature coefficient of resonant frequency (τf) = −7.3 ppm/°C and dielectric constant (?r) = 11.7. Addition of 10 wt% of BBSZ lowered the sintering temperature to about 950 °C with Qu × f > 10,000 GHz, ?r = 10 and τf = −23 ppm/°C. The reactivity of 10 wt% BBSZ added ZAT with silver was also studied. The results show that ZAT doped with suitable amount of BBSZ glass is a possible material for low-temperature co-fired ceramic (LTCC) application. 相似文献
4.
S. Bala Murali Krishna 《Materials Research Bulletin》2010,45(12):1783-1791
ZnO-Sb2O3-As2O3 transparent glasses containing small concentrations of chromium ions (introduced as Cr2O3) ranging from 0 to 0.2 mol% is prepared. A number of studies viz., XRD, SEM, DTA, optical absorption, FT-IR, Raman, ESR spectra, magnetic susceptibility and dielectric properties (constant ?′, loss tan δ, ac. conductivity σac over a wide range of frequency and temperature as well as dielectric breakdown strength at room temperature) of these glasses have been carried out as a function of chromium ion concentration. The results have been analysed in the light of different oxidation states of chromium ions. The analyses indicates that when the concentration of chromium ions is low, these ions mostly exist in Cr6+ and Cr5+ states, occupy network forming positions with CrO42− and CrO43− structural units respectively and increase the rigidity of the glass network. When the concentration of chromium ions is gradually increased, these ions seem to be existing mostly in Cr3+ state. 相似文献
5.
A ChahineM Et-tabirou 《Materials Research Bulletin》2002,37(12):1973-1979
(50−x)Na2O-xCuO-10Bi2O3-40P2O5 glasses (0≤x≤25) were prepared by melting at 900-1100°C mixtures of Na2CO3, Bi2O3, CuO and (NH4)2HPO4. DSC measurements give the variation of glass transition temperature Tg from 318 (x=0) to 378°C (x=25). FTIR spectroscopy shows the evolution of the phosphate skeleton: (PO3)∞ chains for 60Na2O-40P2O5 to P2O7 groups in the glass containing Bi2O3 or both Bi2O3 and CuO. When bismuth and copper oxides replace Na2O, phosphate chains are depolymerized by the incorporation of Bi2O3 and CuO through POBi and POCu bonds. P2O7 groups are predominant structural units in the richest CuO glass. The variation of Tg also supports these results. 相似文献
6.
Jie Fu 《Materials Research Bulletin》2011,46(12):2523-2526
Binary TiO2-P2O5 glasses with 69 mol% and 76 mol% TiO2 were prepared and converted into glass ceramics by heat-treatments. XRD measurements show that the main crystalline phases precipitated in the glass ceramics are anatase-type TiO2 crystals or (TiO)2P2O7 crystals, depending on the concentration of titanium constituent. Photocatalytic activities of the glass ceramics were evaluated by the decomposition of methylene blue (MB) and measuring the water contact angle. It is found that the glass ceramics containing anatase crystals exhibit both photocatalytic oxidation activity and highly photo-induced hydrophilicity under UV irradiation with intensity of 1.0 mW/cm2. 相似文献
7.
T.V. Serov E.I. Ardashnikova V.A. Dolgikh Mohamed El Omari J. Senegas A.M. Abakumov 《Materials Research Bulletin》2005,40(5):821-830
A fluorite-like solid solution Ba1 − xBixOzF2 + x − 2z on the basis of cubic BaF2 was synthesised in the BaF2-Bi2O3-BiF3 system and the homogeneity range at 873 K was determined. The samples were studied by X-ray powder diffraction and electron diffraction, and their transport properties were measured by the complex impedance method at 300-623 K. Tendencies of variation of lattice parameters and transport properties were determined. These tendencies are discussed on the basis of a defect clustering hypothesis. Thermal treatment at 573 K of the solid solution, quenched from 873 K results in the formation of a new ordered tetragonal fluorite-like phase with lattice parameters a = 9.5355(4) Å, c = 18.151(1) Å. 相似文献
8.
0.60Na2O-0.40P2O5 and (0.55−z)Na2O-0.05Bi2O3-zTiO2-0.40P2O5 glasses (0≤z≤0.15) were prepared by melting at 1000°C mixtures of Na2CO3, Bi2O3, TiO2 and (NH4)2HPO4. Differential Scanning Calorimetry (DSC) measurements give the variation of glass transition temperature (Tg) from 269°C (for 0.60Na2O-0.40P2O5) to 440°C (for z=0.15). The density measurements increases from 2.25 to 3.01 g/cm3. FTIR spectroscopy shows the evolution of the phosphate skeleton: (PO3)∞ chains for 0.60Na2O-0.40P2O5 to P2O74− groups in the glasses containing Bi2O3 or both Bi2O3 and TiO2. When bismuth oxide and titania are added to sodium phosphate glass, phosphate chains are depolymerized by the incorporation of distorted Bi(6) and Ti(6) units through POBi and POTi bonds. Bi2O3 and TiO2 are assumed to be present as six co-ordinated octahedral [BiO6/2]3−and [TiO6/2]2− units again with shared corners. This is accompanied by the simultaneous conversion of [POO3/2] into [PO4/2]+ units which achieves charge neutrality in the glasses. 相似文献
9.
Marko Hrovat Andreja Ben?an Janez Holc Tadej Rojac Marija Kosec 《Materials Research Bulletin》2011,46(1):98-100
Subsolidus equilibria in air in the RuO2-Bi2O3-ZrO2 system were studied with the aim of obtaining information on possible interactions between a Bi2Ru2O7-based cathode and a ZrO2-based solid electrolyte in solid-oxide fuel cells (SOFCs). No ternary compound was found in the system. The tie lines are between Bi2Ru2O7 and ZrO2, and between Bi2Ru2O7 and gamma-Bi2O3—the ZrO2 stabilised Bi2O3 phase, stable at temperatures over 710 °C. 相似文献
10.
Wen-Cheng Tzou Sang-Li ChangCheng-Fu Yang Ying-Chung Chen 《Materials Research Bulletin》2003,38(6):981-989
The microwave characteristics and the microstructures of 0.88Al2O3-0.12TiO2 with various amounts of MgO-CaO-SiO2-Al2O3 (MCAS) glass sintered at different temperatures have been investigated. The sintering temperature can be lowered to 1300 °C by the addition of MCAS glass. The densities, dielectric constants (εr) and quality values (Q×f) of the MCAS-added 0.88Al2O3-0.12TiO2 ceramics decrease with the increase of MCAS glass content. The temperature coefficients of the resonant frequency (τf) are shifted to more negative values as the MCAS content or the sintering temperatures increase. The change of the crystalline phases of Al2TiO5 phase and rutile-TiO2 phase has profound effects on the microwave dielectric properties of the MCAS-added Al2O3-TiO2 ceramics. As sintered at 1250 °C, 0.88Al2O3-0.12TiO2 ceramics with 2 wt.% MCAS glass addition exists a εr value of 8.63, a Q×f value of 9578 and a τf value of +5 ppm/°C. 相似文献
11.
Crystalline Na3Bi2P3O12, K3Bi2P3O12 and glassy K3Bi2P3O12 compounds were prepared by solid-state reaction method. The prepared samples are characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy and differential scanning calorimetry. The crystalline materials are found to be orthorhombic. The electrical conductivity measurements on the crystalline and glassy samples show that at ∼373 K, the σDC for crystalline K3Bi2P3O12 (0.81 × 10−8 S/cm) is about two orders of magnitude higher than the corresponding glassy phase (1.25 × 10−10 S/cm). The scaling results show that the conductivity relaxation mechanism is independent of temperature. 相似文献
12.
K. Yasuda 《Materials Research Bulletin》2010,45(9):1278-11034
Pt/CeO2-ZrO2-Bi2O3 catalysts for catalytic combustion of acetaldehyde, which is one of volatile organic compounds (VOCs), were prepared by a wet impregnation method in the presence of polyvinylpyrrolidone K25 (PVP). The addition of PVP in the preparation process was effective to enhance the specific surface area and the Pt2+ ratio on the surface. Additionally, the pore volume and size of the catalysts were modified by the PVP addition. The Pt/CeO2-ZrO2-Bi2O3 catalysts are specific for the total acetaldehyde oxidation and CO and any acetaldehyde-derivative compounds were not observed as by-products. The catalytic activity of the Pt/CeO2-ZrO2-Bi2O3 catalysts was significantly promoted by the PVP addition and the total oxidation temperature decreased. By the optimization of the amount of platinum, the complete oxidation of acetaldehyde was realized at a temperature as low as 140 °C on a 10 wt%Pt/CeO2-ZrO2-Bi2O3 catalyst. 相似文献
13.
In this work, X-ray diffraction, Raman spectroscopy and differential scanning calorimetry techniques were used to understand the crystallization process on 20Li2O-80TeO2 glass. X-ray diffraction results reveal the presence of three distinct alpha γ-TeO2, α-TeO2 and α-Li2Te2O5 crystalline phases in the glass matrix. The Raman spectroscopy band structure of this glass is similar to the one observed in glassy TeO2. Raman results clearly reveal the metastable character of the γ-TeO2 phase in the 20Li2O-80TeO2 glass, whose associated vibration modes disappear completely at temperatures higher than 315 °C. On the other hand, the Raman modes associated to α-TeO2 and α-Li2Te2O5 phases persists up to temperatures close to the final stages of the crystallization in the studied glass (around 420 °C). From DSC measurements, the activation energies 296 ± 3 and 298 ± 1 kJ mol−1 were associated to γ-TeO2 and α-TeO2 phases crystallization, indicating that these phases crystallizes at temperatures very close in the studied glass. 相似文献
14.
Influence of Sm2O3 on the crystallization and luminescence properties of boroaluminosilicate glasses
Sm2O3-doped SiO2-B2O3-Al2O3-BaO glasses were prepared by melting method in order to study the influence of Sm2O3 on the crystallization behavior and luminescence properties. Differential scanning calorimetry (DSC), X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy were used to characterize the rare earth glasses and the crystalline phases after heat-treatment. The course of phase separation and devitrification of the glasses were also investigated. The results show that the thermal stability of the glasses decreases with the increase of content of Sm2O3. The crystalline phase changed from SmAl2.07(B4O10)O0.6 to SmBO3. Divalent Sm2+ ions were detected in the crystallization product after heat-treatment. The valence transformation from Sm3+ to Sm2+ in the crystal suggests the samarium atoms entering the barium sites. The charge carried in vacancy defect induced by the substitution led to the partial reduction process. The reduction of Sm3+ ions was promoted by the increasing of Sm2O3 content or the extending of heat-treated holding time in boroaluminosilicate glass. 相似文献
15.
Karima Horchani Mokhtar FeridJean-Claude Gacon Sylvain LecocqMalika Trabelsi-Ayedi Ivan Gregora 《Materials Research Bulletin》2002,37(7):1259-1267
Crystals of KDyP4O12 have been grown by the flux technique and characterized by single-crystal X-ray diffraction. KDyP4O12 crystallizes in the monoclinic C2/c space group with lattice parameters: a=7.8158(3), b=12.3401(5), c=10.4382(3) Å, β=111.053°(2), V=939.6(4) Å3, Z=4. The crystal structure has been refined yielding a final R(F2)=0.034 and Rw(F2)=0.082 for 902 independent reflections (Fo2≥2σ(Fo2)). The structure of KDyP4O12 consists of DyO8 polyhedra and cyclotetraphosphate P4O12 groups sharing oxygen atoms to form a three-dimensional framework, delimiting intersecting tunnels in which the potassium ion is located. Each K+ ion is bonded to 10 oxygen atoms. The energies of the vibrational modes of the crystal were obtained from measurements of the infrared and Raman spectra. 相似文献
16.
C. Narayana Reddy 《Materials Research Bulletin》2007,42(7):1337-1347
Glass systems of the composition xLi2O-20ZnO-(80 − x)B2O3 where (x = 5, 10, 15, 20, 25 and 30 mol%) have been prepared by melt quenching technique. Elastic properties, 11B MAS-NMR and IR spectroscopic studies have been employed to study the structure of Li2O-ZnO-B2O3 glasses. Elastic properties have been investigated using sound velocity measurements at 10 MHz. Elastic moduli reveal trends in their compositional dependence. The bulk modulus and shear modulus increases monotonically with increase of BO4 units, which increase the dimensionality of the network. 11B MAS-NMR and IR spectra show characteristic features of borate network and compositional dependent trends as a function of Li2O/ZnO concentration. The results are discussed in view of borate network and the dual structural role of Zn2+ ions. The results indicate that the Zn2+ are likely to occupy network-forming positions in this glass system. 相似文献
17.
Porous ultrafine Fe2O3 particles were prepared by homogeneous precipitation method. Fe3+ and urea were chosen as starting materials and anionic surfactant as the template. It is shown that the reaction results in the precipitation of a gelatinous hydrous iron oxide/surfactant mixture, which gives ultrafine Fe2O3 particles after drying and calcinations. The products were characterized by XRD, TEM, TG/DTA and BET. Conventional XRD patterns show that the products are mixture of γ-Fe2O3 and α-Fe2O3 phase after being sintered at 350 °C, and γ-Fe2O3 transforms entirely to α-Fe2O3 when sintered at 650 °C. The low-angle XRD patterns indicate that the mesostructure can only exist between 350 and 400 °C. TEM results show that the Fe2O3 particles have diameters of about 30 nm and lengths ranging from 100 to 120 nm; in each particle, there are several vermiculate-like mesopores with diameter of about 20-25 nm. The BET surface areas in excess of 50 m2/g are obtained after calcinations at 350 °C. The BJH desorption average pore width is around 22 nm, which is in agreement with the TEM results. The results show that anionic surfactant and sintering temperature are important to obtain this special morphology. 相似文献
18.
2-6 mol% ZrO2 was added to a base glass composition of P2O5 31.25, CaO 43.75, TiO2 25 (mol%) at the expense of TiO2. The prepared glasses were crystallized to bulk glass ceramics containing the major phases of β-Ca3(PO4)2 and CaTi4(PO4)6. DTA was utilized to determine the appropriate phase separation-nucleation and crystallization temperatures. The crystalline products and resulting microstructures were examined by XRD and SEM. The β-Ca3(PO4)2 phase was dissolved out by leaching the resulting glass ceramics in HCl, leaving a porous skeleton of CaTi4(PO4)6. It was shown that ZrO2 addition resulted in reduction of volume porosity and mean pore diameter while the specific surface area was increased. The smallest median pore diameter and largest surface area were 8.6 nm and 32 m2 g−1 respectively obtained for the specimen containing 6 mol% ZrO2. The ZrO2 addition also improved the chemical durability and bending strength of porous glass ceramics. 相似文献
19.
Crystals of RbPrHP3O10 have been grown by the flux technique and characterized by single-crystal X-ray diffraction. RbPrHP3O10 crystallizes in the triclinic space group with lattice parameters: a = 7.0655(5), b = 7.7791(4), c = 8.6828(6) Å, α = 74.074(3), β = 74.270(3), γ = 82.865(2)°, V = 441.09(5) Å3, Z = 2. The crystal structure has been solved yielding a final R(F2) = 0.0443 and Rw(F2) = 0.1426 for 1955 independent reflections (Fo2 ≥ 2σ(Fo2)). The structure of RbPrHP3O10 consists of PrO8 polyhedra and P3O105− groups sharing oxygen atoms to form a two-dimensional framework; the PrO8 polyhedra form infinite chains by edge-sharing. Each Rb+ ion is bonded to 10 oxygen atoms, these ions are located between chains formed of (HP3O10)4−. The energies of the vibrational modes of the crystal were obtained from measurements of the infrared spectrum. 相似文献
20.
B Karthikeyan 《Materials Research Bulletin》2004,39(10):1507-1515
New developments in photonic technology need new materials for various applications. In the present report, Nd3+-doped NaF-Na2O-B2O3 glasses were prepared and the spectroscopic and glass transition properties were analysed. The Fourier transform infrared spectral studies reveal that the glass contains BO3 and BO4 units as the local structures and the Na+ ions as the network modifiers. The absorption studies were carried out by using Judd-Ofelt theory, the experimental and theoretical oscillator strengths were also calculated. The emission spectral study was done for the 1 mol% Nd-doped glass and the spontaneous emission probability and stimulated emission cross-sections for the , transitions were calculated using the J-O parameters. 相似文献