共查询到20条相似文献,搜索用时 31 毫秒
1.
H. Doweidar 《Journal of Materials Science》2009,44(11):2899-2906
Refractive index and molar refraction of Li2O–, Na2O–, CaO–, and BaO–Ga2O3–SiO2 glasses have been used to test the validity of a structural model of silicate glasses containing Ga2O3 glasses. Ga2O3 enters these types of glass in a similar manner as Al2O3. It is assumed that, for (SiO2/Ga2O3) >1 and (Ga2O3/R2O) ≤1, Ga2O3 associates primarily with modifier oxides to form GaO4 units. The rest of modifier oxide forms silicate units with non-bridging oxygen ions. Silicate structural units have the
same factors as found for binary alkali- and alkaline earth silicate glasses. Differences between experimental and model values
suggest another structure for (Ga2O3/SiO2) ≥1. 相似文献
2.
Moo-Chin Wang Huy-Zu Cheng Huey-Jiuan Lin Chien-Fu Wang Chi-Shiung Hsi 《Materials Chemistry and Physics》2013
The crystallization behavior and magnetic properties of 10Li2O–9MnO2–16Fe2O3–25CaO–5P2O5–35SiO2 (10LFS) glass have been studied using differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) to observe the crystallization behavior and a superconducting quantum interference device (SQUID) for measurements of the magnetic properties. The DTA shows that the 10LFS glass has one broad exothermic peak at approximately 674 °C and one sharp (the highest) exothermic peak at 764 °C. When the 10LFS glass crystallized at 850 °C for 4 h, the crystalline phases identified by XRD were lithium silicate (Li2SiO3), β-wollastonite (β-CaSiO3), lithium orthophosphate (Li3PO4), magnetite (FeFe2O4) and triphylite (Li(Mn0.5Fe0.5)PO4). The SEM surface analysis revealed that the β-wollastonite and lithium silicate have a lath morphology. The TEM microstructure examination showed that the largest FeFe2O3 particles have a size of approximately 0.3 μm. When the 10LFS glass was heat treated at 850 °C for 16 h and a magnetic field of 1000 Oe was applied, a very small remnant magnetic induction of 0.01 emu g−1 and a coercive force of 50 Oe were obtained, which revealed an inverse spinel structure. 相似文献
3.
A magnetic SO42−/ZrO2–B2O3–Fe3O4 solid superacid catalyst is prepared via a simple chemical co-precipitation approach. The obtained materials were characterized in detailed by X-ray powder diffraction, thermogravimetric analysis–different scanning calorimetry, Fourier transform infrared spectroscopy (FTIR), electron microscopy (SEM and TEM), and Mossbauer spectra. Powder X-ray diffraction patterns show that in this composite oxide the transformation temperature of ZrO2 from tetragonal to monoclinic phase is higher compared to the pristine SO42−/ZrO2 material. The introduction of Fe3O4 endows the superacid with a super-paramagnetic property while in a ferromagnetic state after calcination. The superacid exhibits high catalytic activity in forming ethyl acetate by esterification. 相似文献
4.
5.
Min Wang Ruzhong Zuo Weiqing Meng Yi Liu 《Journal of Materials Science: Materials in Electronics》2011,22(7):843-848
The CaO–B2O3–SiO2 glass/CaSiO3 ceramic (CBS/CS) composites were fabricated via sol–gel processing routes. Their densification behavior, structures and dielectric
properties were investigated. The precursors of CBS glass and CS ceramic filler were firstly obtained via individual soft
chemical route and then mixed together in various proportions. The results indicated that the structures of CBS/CS composites
are characteristic of CS and CaB2O4 (CB) ceramic phases distributed in the matrix of glass phase at 800–950 °C. The CS ceramic phase not only acts as fillers,
but nuclei for the crystallization of CBS glass as well such that the CS content exhibits an effect on the densification and
dielectric properties of the composites. The CBS/CS composites with 10% CS sintered at 850 °C own dielectric properties of
εr < 5 and tanδ = 6.4 × 10−4 at 1 MHz. 相似文献
6.
Ivana R?sslerová Ladislav Koudelka Zdeněk ?erno?ek Petr Mo?ner Ludvík Bene? 《Journal of Materials Science》2011,46(20):6751-6757
Thermal properties and crystallization of glasses from PbO–MoO3–P2O5 ternary system were studied in three compositional series (100 − x)[0.5PbO–0.5P2O5]–xMoO3 (A), 50PbO–yMoO3–(50 − y)P2O5 (B), and (50 − z)PbO–zMoO3–50P2O5 (C). Glass transition temperature, crystallization temperature, coefficient of thermal expansion, and dilatation softening
temperature of the studied glasses were determined by differential thermal analysis and dilatometry. Crystallization products
of annealed glass samples were investigated by X-ray diffraction and Raman spectroscopy. X-ray diffraction analysis of crystallized
glasses revealed the formation of PbP2O6, Pb3P4O13, and PbMoO4 in the samples of the B series. In the series A and C in the samples with a high MoO3 content, crystalline compounds of Pb(MoO2)2(PO4)2 and (MoO2)(PO3)2, respectively, were identified. Raman spectra of crystalline samples confirmed the results of X-ray diffraction measurements
and provided also information on thermal stability of glasses and formation of glass-crystalline phases in the studied glass
series. 相似文献
7.
Xiangquan Jiao Chaowei Zhong Shuren Zhang Xingshu Liu Bo Li 《Journal of Materials Science》2010,45(12):3331-3335
Besides the applications as optical functional materials, tellurium oxides also have attracted interest as microwave dielectric
materials. Most TeO2-based binary and ternary system have large negative temperature coefficient of resonant frequency (τf), which is not compatible for the low-temperature cofired ceramic. To compensate τf close to zero, two single-phase predecessors of BaTe4O9 and TiTe3O8 are synthesized in air at 530–560 and 620–680 °C, respectively. The two predecessors show exceptional dielectric properties
and their τf are opposite. The BaO–TiO2–TeO2 ternary system compounds are investigated by adjusting the ratio of BaTe4O9 and TiTe3O8 and sintered at 520–580 °C to develop the microwave properties and compensate the τf. After sintered at 560 °C, the ceramic sample with the composition of 0.47BaTe4O9–0.53TiTe3O8 exhibits a dielectric permittivity of 28, a Q × f-value of 12,200 GHz, and a τf of 4.0 ppm/°C measured at 10 GHz. 相似文献
8.
Atiar Rahaman Molla Anal Tarafder Basudeb Karmakar 《Journal of Materials Science》2011,46(9):2967-2976
Glasses were prepared by the melt-quench technique in the K2O–SiO2–Bi2O3–TiO2 (KSBT) system and crystallized bismuth titanate, BiT (Bi4Ti3O12) phase in it by controlled heat-treatment at various temperature and duration. Different physical, thermal, optical, and
third-order susceptibility (χ3) of the glasses were evaluated and correlated with their composition. Systematic increase in refractive index (n) and χ3 with increase in BiT content is attributed to the combined effects of high polarization and ionic refraction of bismuth and
titanium ions. Microstructural evaluation by FESEM shows the formation of polycrystalline spherical particles of 70–90 nm
along with nano-rods of average diameter of 85–90 nm after prolonged heat treatment. A minor increase in dielectric constants
(εr) has been observed with increase in polarizable components of BiT in the glasses, whereas a sharp increase in εr in glass–ceramics is found to be caused by the formation of non-centrosymmetric and ferroelectric BiT nanocrystals in the
glass matrix. 相似文献
9.
Changrong Zhou Xinyu Liu Weizhou Li Changlai Yuan Guohua Chen 《Journal of Materials Science》2009,44(14):3833-3840
Lead-free piezoelectric ceramics (1 − x − y)Bi0.5Na0.5TiO3–xBi0.5K0.5TiO3–yBiCoO3 (x = 0.12–0.24, y = 0–0.04) have been fabricated by a conventional solid-state reaction method, and their structure and electrical properties
have been investigated. The XRD analysis shows that samples with y ≤ 0.03 exhibit a pure perovskite phase and very weak impurity reflections can be detected in the sample with y = 0.04. With x increasing from 0.12 to 0.24 and y increasing from 0 to 0.04, the ceramics transform gradually from a rhombohedral phase to a tetragonal phase and rhombohedral–tetragonal
phase coexistence to a pseudocubic phase, respectively. The morphotropic phase boundary (MPB) of the system between rhombohedral
and tetragonal locates in the range of x = 0.18–0.21, y = 0–0.03. The ceramics near the composition of the MPB have good performances with piezoelectric constant d
33 = 156 pC/N and electromechanical coupling factor k
p = 0.34 at x = 0.21 and y = 0.01, which attains a maximum value in this ternary system. Adding content of BiCoO3 leads to a disappearance of the response in the curves of dielectric constant-temperature to the ferroelectric–antiferroelectric
transition. The temperature dependence of dielectric properties suggests that the ceramics are relaxor ferroelectrics. The
results show that (1 − x − y)Bi0.5Na0.5TiO3–xBi0.5K0.5TiO3–yBiCoO3 ceramics are good candidate for use as lead-free ceramics. 相似文献
10.
Manish S. Jayswal D.K. Kanchan Poonam Sharma Nirali Gondaliya 《Materials Science and Engineering: B》2013,178(11):775-784
Silver ion conducting super-ionic glass system xPbI2–(100 − x) [Ag2O–2(V2O5–B2O3)], where, 5 ≤ x ≤ 25, were prepared via melt quenching route and -characterized by XRD and DSC. Their electrical properties were measured by impedance spectroscopy in the frequency range of 2 MHz to 20 Hz from 30 to 120 °C. The electrical relaxation mechanism has been studied using AC conductivity, dielectric modulus function and frequency dependent dielectric permittivity over a wide range of frequency and temperature. Two different scaling approaches for AC conductivity as well as dielectric permittivity spectra were used to understand the nature of relaxation processes. 相似文献
11.
0.09(Bi0.5Na0.5)0.94Ba0.06TiO3–(0.01 − x) Bi0.5(Na0.82K0.18)0.5TiO3–x BiAlO3 (BNBKT–xBA) lead-free piezoelectric ceramics were synthesized by conventional solid-state reaction processes. Structure, ferroelectric and piezoelectric properties of BNBKT–xBA ceramics were investigated. X-ray diffraction data shows that BNBKT–xBA ceramics form the pure perovskite phases and the ceramics have the morphotropic phase boundary when x ≤ 0.030. At room temperature, the BNBKT–xBA ceramics at x = 0.030 have better electrical properties, the piezoelectric constant d33 and planar coupling factor kp of BNBKT–xBA ceramics reaches peak values at x = 0.030: d33 = 217 pC N−1, kp = 0.308. The remnant polarization Pr, mechanical quality factor Qm and relative dielectric constant ?r of BNBKT–xBA ceramics at x = 0.030 attains 33.8 μC cm−2, 133 and 928 (100 KHz), respectively. As BA content increase, the depolarization temperature Td shift toward lower temperature, and Td of BNBKT–xBA ceramics with x = 0.030 decreased to 55 °C. 相似文献
12.
The phases, microstructure and microwave dielectric properties of ZnNb2O6–xCaTiO3 ceramics with BaCu(B2O5) glass additions prepared by solid state reaction method were charactered by using X-ray diffraction, Scanning electron microscopy and Advantest network analyzer. The τf of ZnNb2O6 was modified to near 0 ppm °C−1 by incorporating CaTiO3 with opposite τf values on the basis of Lichtenecker empirical rule. The microwave dielectric properties of ZnNb2O6–xCaTiO3 (x = 8.0 wt.%) samples with BaCu(B2O5) glass additives sintered in 900–1000 °C were investigated, and the results indicated that the behaviors of the εr and Q × f were associated with the sintering temperature and the amount of BaCu(B2O5) glass. The sintering temperature of the ceramics was reduced to 950 °C from 1175 °C. Addition of 5.0 wt.% BaCu(B2O5) glass in ZnNb2O6–xCaTiO3 (x = 8.0 wt.%) ceramics sintered at 950 °C showed excellent dielectric properties of εr = 20.2, Q × f = 14,100 GHz (f = 7.3 GHz) and τf = 0 ppm °C−1. Moreover, the material had a chemical compatibility with silver, which represented a promising candidate materials for low-temperature-co-fired ceramics applications. 相似文献
13.
Bo Li Shuren Zhang Ying Yuan Xiaohua Zhou Longcheng Xiang 《Journal of Materials Science》2009,44(18):4993-4998
The low-fired (ZnMg)TiO3–TiO2 (ZMT–TiO2) microwave ceramics using low melting point CaO–B2O3–SiO2 as sintering aids have been developed. The influences of Mg substituted fraction on the crystal structure and microwave properties
of (Zn1−x
Mg
x
)TiO3 were investigated. The result reveals that the sufficient amount of Mg (x ≥ 0.3) could inhibit the decomposition of ZnTiO3 effectively, and form the single-phase (ZnMg)TiO3 at higher sintering temperatures. Due to the compensating effect of rutile TiO2 (τf = 450 ppm/°C), the temperature coefficient of resonant frequency (τf) for (Zn0.65Mg0.35)TiO3–0.15TiO2 with biphasic structure was adjusted to near zero value. Further, CaO–B2O3–SiO2 addition could reduce the sintering temperature from 1150 to 950 °C, and significantly improve the sinterability and microwave
properties of ZMT–TiO2 ceramics, which is attributed to the formation of liquid phases during the sintering process observed by SEM. The (Zn0.65Mg0.35)TiO3–0.15TiO2 dielectrics with 1 wt% CaO–B2O3–SiO2 sintered at 950 °C exhibited the optimal microwave properties: ε ≈ 25, Q × f ≈ 47,000 GHz, and τf ≈ ± 10 ppm/°C. 相似文献
14.
The influence of SrO (0·0–5·0 wt%) on partial substitution of alpha alumina (corundum) in ceramic composition (95 Al2O3–5B2O3) have been studied by co-precipitated process and their phase composition, microstructure, microchemistry and microwave dielectric
properties were studied. Phase composition was revealed by XRD, while microstructure and microchemistry were investigated
by electron-probe microanalysis (EPMA). The dielectric properties by means of dielectric constant (ε
r
), quality factor (Q × f) and temperature coefficient of resonant frequency (τ
f
) were measured in the microwave frequency region using a network analyser by the resonance method. The addition of B2O3 and SrO significantly reduced the sintering temperature of alumina ceramic bodies to 1600 °C with optimum density (∼ 4g/cm3) as compared with pure alumina powders recycled from Al dross (3·55g/cm3 sintered at 1700 °C). 相似文献
15.
Bi4Ti3O12–(Ni0.5Zn0.5)Fe2O4 dielectric–ferromagnetic ceramic composites synthesized with nanopowders
Bi4Ti3O12 and (Ni0.5Zn0.5)Fe2O4 nanopowders were prepared by co-precipitation and hydrothermal methods, respectively. It was found that ethanolamine is effective as a precipitating agent in the synthesis of Bi4Ti3O12 nanopowders via co-precipitation, and it also plays an important role in the synthesis of (Ni0.5Zn0.5)Fe2O4 nanopowders. Bi4Ti3O12–(Ni0.5Zn0.5)Fe2O4 multiferroic ceramics were obtained by sintering the as-prepared nanopowders. Lower sintering temperatures (800–900 °C) were available when compared with the traditional solid state method and ceramic composites with higher density and limited interfacial reaction were obtained. The ceramics also showed lower dielectric loss and higher magnetic moments. Both the ferroelectric and magnetic phases preserve their individual properties in bulk composite form and thus, these types of composite ceramics appear to be good candidate multiferroic materials. 相似文献
16.
Feng Ni Laihui Luo Xiaoyin Pan Yuepin Zhang Hongbing Chen 《Journal of Materials Science》2012,47(7):3354-3360
Lead-free piezoelectric ceramics (1 − x)Bi0.5(Na0.84K0.16)0.5TiO3–xBa0.77Ca0.23TiO3 (BNKT–xBCT, x = 0–0.04) were synthesized by conventional solid-state reaction method. The piezoelectric, dielectric, and ferroelectric
characteristics of the ceramics are investigated and discussed. The XRD results show that Ba0.77Ca0.23TiO3 (BCT) has diffused into Bi0.5(Na0.84K0.16)0.5TiO3 (BNKT) lattices to form a new solid solution. It is shown that moderate additive of BCT (x ≤ 0.025) in BNKT–xBCT ceramics can enhance their piezoelectric and ferroelectric properties. Three dielectric anomalies are observed in BNKT–xBCT (x ≤ 0.03) ceramics. The piezoelectric measurements and P–E hysteresis loops reveal that BNKT–0.025BCT ceramic has the highest piezoelectric performance and strongest ferroelectricity
in all the samples. Piezoelectric constants d
33, k
p, and k
t of 175 pC/N, 29.1, and 54% are, respectively, achieved. Remnant polarization P
r and coercive field E
c reach 28.3 μC/cm2 and 24.2 kV/cm, respectively. 相似文献
17.
The effects of the annealing of 20BaO–30V2O5–50Bi2O3 glass on the structural and electrical properties were studied by scanning electron micrographs (SEM), X-ray diffraction (XRD), differential scanning calorimeter (DSC) density (d) and dc conductivity (σ). The XRD and SEM observations have shown that the sample under study undergoes structural changes: from amorphous at the beginning, to partly crystalline after nanocrystallization at crystallization temperature (Tc) for 1 h and to colossal crystallization after the annealing at the same temperature for 24 h. The average size of these grains after nanocrystallization at Tc for 1 h was estimated to be about 25–35 nm. However, the glass heat treated at Tc = 580 °C for 24 h the microstructure changes considerably. The nanomaterials obtained by nanocrystallization at Tc for 1 h exhibit giant improvement of electrical conductivity up to four order of magnitude and better thermal stability than the as-received glass. The major role in the conductivity enhancement of this nanomaterial is played by the developed interfacial regions “conduction tissue” between crystalline and amorphous phases, in which the concentration of V4+–V5+ pairs responsible for electron hopping is higher than inside the glassy matrix. The annealing at Tc for 24 h leads to decrease of the electronic conductivity. This phenomena lead to disappearance of the abovementioned “conduction tissue” for electrons and substantial reduction of electronic conductivity. The high temperature (above θ/2) dependence of conductivity could be qualitatively explained by the small polaron hopping (SPH) model. The physical parameters obtained from the best fits of this model are found reasonable and consistent with the glass compositions. 相似文献
18.
In this article, the wetting of 23 wt% CaO–15 wt% Al2O3–62 wt% SiO2 molten glass on polycrystalline silicon carbide is studied under air at temperatures between 1,100 and 1,590 °C. Wetting
experiments are performed by the sessile drop technique. Good wetting (final contact angle lower than 50°) is observed regardless
of the experimental temperature when it is higher than 1,300 °C. Moreover, some specific experiments of wetting of glass on
platinum, silica and monocrystalline SiC substrates are also performed. The character of molten glass spreading on silicon
carbide (reactive or non-reactive) as well as the role of the atmosphere on interfacial interactions with SiC are identified
and discussed. 相似文献
19.
Y. Y. Chen P. C. Chen C. B. Tsai K. I. Suga K. Kindo 《International Journal of Thermophysics》2009,30(1):316-324
Thermometers consisting of RuO2–Al2O3 composite thin films were prepared by RF sputtering. It was found that different electrode-patterning techniques have dissimilar
effects on the magnetoresistance (MR) and the temperature coefficient of resistance (TCR). In general, the thermometers with
electrodes fabricated by photo-resist lithography exhibit superior performance compared to those with electrodes prepared
using a metal mask. By adjusting the relative compositions of RuO2 and Al2O3, the thermometers can be applied to a wide temperature range from 60 mK to 500 K. In a pulsed magnetic field up to 55 T,
the MR at 4.2 K of a typical thermometer for the temperature range from 1.4 K to 300 K increases linearly with magnetic field
to a maximum of ~15 %, corresponding to a temperature deviation of ~−4 %. As frequency increases from dc to 1.9 MHz, the MR
decreases from −13 % to ~ − 0.5 % at T = 1.3 K and H = 55 T. By integrating the thermometer with a heater on a sapphire chip, a micro-calorimeter can be developed and successfully
used to measure the heat capacity of small mg-sized sample. The RuO2–Al2O3 composite film can also be employed as an infrared bolometer operated at room temperature. 相似文献
20.
WOx–ZrO2 support was calcined at various temperatures for obtaining controllable activity of copper catalysts for NOx reduction by ammonia. The temperature window of copper catalyst for over 80% NOx conversion shifts from 180–300 to 230–350 °C by elevating the calcination temperature of WOx–ZrO2 support from 500 to 600 °C, due to the increased Brønsted acidity and reduced structure and electronic interactions between copper oxides and tungsten oxides arising from the polymerization of WOx clusters on surface of support. Calcining WOx–ZrO2 support at 700 °C leads to the reduced redox property of copper oxides on the Cu–O–W interface and the formation of bulk-like CuO, results in a low activity of catalyst. 相似文献