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1.
De -An Chang Yi -Hung Choh Wen -Feng Hsieh Pang Lin Tseung -Yuen Tseng 《Journal of Materials Science》1993,28(24):6691-6698
Films of Pb
x/100La
x/100(Zr
y/100Ti
z/100)1–x/400O3 with x=8, y=65 and z=35 (PLZT(8/65/35)) with a single perovskite structural phase were successfully prepared by using drying-control chemical additives in sol-gel processing followed by rapid thermal annealing at 600 °C for only 1 min on Si(Pt) substrates. The roles of the drying-control chemical additives ethylene glycol and formamide in the gel preparation were studied. The hysteresis loop of PLZT(8/65/35) thin film was measured. The remanent polarization and coercive field were found to be about 1.3 C cm–2 and 15 kVcm–1, respectively. 相似文献
2.
The elastic properties of two series of lanthanum aluminosilicate glasses (15La2O3-xAl2O3-(85−x)SiO2 and 25La2O3-yAl2O3-(75−y)SiO2, where x, y=15, 20, 25, 30, 35 mol%), were obtained by the ultrasonic pulse-echo technique, at room temperature. The correlation of elastic stiffness, the cross-link density, and the fractal bond connectivity of these glasses are discussed. The derived experimental values of Young’s modulus, bulk modulus, shear modulus and Poisson’s ratio for our glasses are compared with those theoretically calculated values in terms of the Makishima-Mackenzie model. 相似文献
3.
We have determined the main characteristics of ceramic materials prepared by modifying 2MgO · 2Al2O3 · 5SiO2 with MnO and FeO. The formation of the ceramics was analyzed by detailed thermal analysis, X-ray diffraction, IR spectroscopy,
and differential scanning calorimetry. We have determined the heat effects of formation of Mg1 − x
M
x
Al2O4 (0.25 < x < 0.75) and Mg2 − y
M
y
Al4Si5O18 (0.5 < y < 1.5) solid solutions with M = Mn(II) and Fe(II) and calculated the standard heats of formation of the Mg1 − x
M
x
Al2O4 and Mg2 − y
M
y
Al4Si5O18 solid solutions. 相似文献
4.
In addition to the dielectric relaxation around 170 K in the cubic structure of Sr1–3x/2La
x
TiO3, a similar relaxation was observed at about 70 K in the tetragonal structure with an activation energy in the range 0.13–0.16 eV which increases as x in Sr1–3x/2La
x
TiO3 varies from 0.60–3.00 at%. This relaxation is explained by Skanavi's model and is discussed in terms of thermal motions of Ti4+ between potential minima produced by lattice distortions in the tetragonal structure. In order to provide a direct evidence for the suggestion that the dielectric relaxation around 170 K in the cubic is due to thermal motions of Ti4+, dielectric properties on manganese-doped specimens, Sr1–3x/2La
x
Mn
y
Ti1–y
),O3 with x=1.40×10–2 and y=0.1×10–2, were investigated because Mn4+ substitutes for Ti4+. As well as the relaxation due to Ti4+, this specimen exhibits another peak due to Mn4+ with an activation energy somewhat smaller than that of Ti4+. The activation energies and the relative intensity of these relaxation processes are explained by the difference in ionic radii of Mn4+ and Ti4+ and the difference in formation energies of a strontium vacancy adjacent to Mn4+ and that to Ti4+, which were calculated theoretically using a shell model. 相似文献
5.
BaTiO3 positive temperature coefficient of resistance ceramics were prepared with the general composition (La0.002Ca
x
Ba0.998–x
) (Ti1.01–y
Mn
y
)O3 ·zSiO2 and sintered in air. The Ca content as well as the amount of doped Mn were varied ranging from 4–20 mol% and 0.02–0.04 mol%, respectively. Up to 4 mol% Si was added using a new method as well as by the classical means as solid silica. In the new method, the desired quantity of Si(OC2O5)4 (Si(OEt)4), contained in dry tetrahydrofurane (THF), was dropped under a slight stream of inert gas into the vigorously stirred aqueous slurry which was manufactured after the calcination process. The addition of Si by this technique was found to result in a homogenization of the microstructure and an improvement in electrical properties. The effect of Si on electrical properties is explained by the influence of the observed second phase on the equilibrium of Ba vacancies. The results of further variation of Ca and Mn contents are presented. 相似文献
6.
Secondary electron emission from a protective layer in AC PDP is known to be dominated by potential emission mechanism, which is sensitive to its energy band structure. Therefore, the secondary electron emission property can be modified by a change in the energy band structure of the protective layer. The addition of controlled amount of titanium oxide into the conventional magnesium oxide protective material might affect the overall voltage characteristics of panels due to the fact that TiO2 has higher dielectric constant than MgO and that the ion radius of Ti is similar to that of Mg. The electrical properties of panels with protective layers evaporated from the starting materials with different [TiO2/(MgO + TiO2)] ratios were investigated. When the [TiO2/(MgO + TiO2)] ratios of 0.1 and 0.15 were used, the panel exhibited a sustaining voltage of 122 V, which was 16 V smaller than that of the pure MgO, without lowering its memory margin. The relative dielectric constant of Mg2–2x
Ti
x
O2 films increased with addition of TiO2 to the pure MgO, however, it then suddenly decreased above the [TiO2/(MgO + TiO2)] ratio of 0.1. The surface roughness of Mg2–2x
Ti
x
O2 had a minimum when the [TiO2/(MgO + TiO2)] ratio in the starting materials was 0.1. The variation trends of the relative dielectric constant and the surface roughness of Mg2–2x
Ti
x
O2 films with increasing [TiO2/(MgO + TiO2)] ratio in the starting materials were found to be consistent with that of the voltage characteristics. 相似文献
7.
Various glasses in the system (65 – x)[SrO · TiO2]-(35)[2SiO2 · B22O3]-(x)La2O3, where x = 1,5,10 (wt%) were prepared by melting in alumina crucible (1375–1575 K). Heat treatment schedules were selected from DTA plots of respective glasses. X-ray diffraction studies of glass ceramic samples containing different concentrations of La2O3 revealed the formation of Sr2B2O5, Sr3Ti2O7 and TiO2 (rutile) phases. The addition of La2O3 results in the development of well formed, elongated crystallites of different phases. Results of the dielectric behaviour demonstrate higher values of dielectric constant for some of the glass ceramic samples. This can be ascribed to the relaxation polarization at the crystal-glass interface due to conductivity differences between crystalline and glassy phases. 相似文献
8.
The effects of sulphur substitution for oxygen on the structure and properties of nonsuperconducting La2–x
Sr
x
CuO4, where x=0.26 and 0.30, have been studied. In La2–x
Sr
x
CuO 4–y
-S
y
, the sulphur-doped samples exhibit superconducting transition at 37–39 K and a larger Meissner effect than undoped samples. It was found that the superconductivity of La2–x
Sr
x
CuO4–y
S
y
is apparently determined by the value of x–y and the strontium concentration region in which La2–x
Sr
x
CuO4 shows superconductivity shifts to higher strontium concentrations with sulphur doping. 相似文献
9.
A method was developed to determine a compositional fluctuation region in Pb1–y
La
y
(Zr
x
Ti1–x
)1–(y/4)O3 (PLZT) solid solution in the tetragonal region. The compositional fluctuation in PLZT extends two-dimensionally on the phase diagram. The method described in this paper utilized the fact that the compositional fluctuation region extends to the composition lines whose lattice spacing corresponds to the higher or lower fluctuation limit. The fluctuation limits of the lattice spacings were estimated from X-ray diffraction analysis. This method revealed that the compositional fluctuation in PLZT is difficult to be eliminated by using a conventional dry method (mixed oxide method). The shape of the region indicated that homogenization of Zr4+ and Ti4+ was more difficult as compared with that of Pb2+ and La3+. 相似文献
10.
The phase equilibria and crystal structures of mixed oxides in the ternary system La2O3-Mn3O4-NiO are studied at 1100°C in air. The projection of the La-Mn-Ni-O phase diagram at 1100°C and
= 0.21 × 105 Pa onto the metal-composition triangle is found to comprise 12 phase fields. The lattice parameters of La2NiO4 (sp. gr. I4/mmm), La3Ni2O7 (sp. gr. Cmcm), La4Ni3O10 (sp. gr. Cmca), and La1 + x
Mn1 − x − y
NiyO3 solid solutions (sp. gr. Pnma, −0.04 ≤ x ≤ 0.05, 0 ≤ y ≤ 0.4) are determined. The composition stability limits of La4Ni3 − y
MnyO10 solid solutions are 0 < y ≤ 0.05. With increasing Ni concentration in La1 + x
Mn1 − x − y
NiyO3, the metal nonstoichiometry decreases from −0.04 ≤ x ≤ 0.05 at y = 0 to x = 0 at y = 0.4.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 7, 2005, pp. 841–848.Original Russian Text Copyright © 2005 by Demina, Cherepanov, Petrov, Klokova. 相似文献
11.
Shen Lin Xiao Dingquan Zhu Jianguo Yu Ping Zhu Jumu Gao Daojiang 《Journal of Materials Synthesis and Processing》2001,9(6):369-373
La-modified (Bi4–x
La
x
)Ti3O12 (abbreviated as BLT) powders were prepared by sol-gel processing methods. The powders were characterized by differential thermal analysis (DTA) and laser-diffraction particle-size analysis. The (Bi4–x
La
x
)Ti3O12 ceramics were prepared from the powders and characterized by X-ray diffraction (XRD). The results indicate that the sol-gel method can be used to prepare nanometer powder for the new types of BLT ferroelectric ceramics. The solid reaction of BLT powders occurs at 730°C approximately resulting in the growth of BLT grain. The average grain size may be varied in the range 60–500 nm, depending on the calcination temperature of the powders. The (Bi4–x
La
x
)Ti3O12 ceramics prepared from the powders were polycrystalline materials with completely monoclinic (Bi4–x
La
x
)Ti3O12 phase. 相似文献
12.
The present letter reported the synthesis of MgO-containing magnetic nanocomposites by calcinations of tailored hydrotalcite-like layered double hydroxides (LDHs) of the type [Mg1 – x – yFe2+yFe3 +x(OH)2]x +(A)x/2·mH2O (y 0; A = CO32 – or SO42 –) precursors at 900°C for 2 h. The results indicate that calcination of LDHs gives rise to the formation of magnetic nanocomposites of MgO and MgFe2O4 spinel ferrite, where MgO formed could disperse and separate MgFe2O4 particles, and MgO itself was also dispersed or embedded uniformly in the MgFe2O4 spinel matrix. Furthermore, initial studies on the bactericidal properties with staphylococcus aureus show that these as-synthesized nanometer-sized materials have significant bactericidal effect, which increases with the increasing volume fraction of MgO. 相似文献
13.
Microstructural investigations and microanalyses of a series of Ba6–x
R
8+2/3x
Ti18O54 ceramics (R = Nd, Gd) revealed that the solid-solubility limit for the isovalent substitution of R
3+ by Bi3+ depends on the composition of the Ba6–x
R
8+2/3x
Ti18O54 phase. For the Nd analogue the solid-solubility limit (y in Ba6–x
(Nd1–y
Bi
y
)8+2/3x
Ti18O54) decreases with a decrease in x from y = 0.16 for x = 2.0 to y = 0.10 for x = 0.8. An even lower solid-solubility limit (y = 0.06) was found for the Ba4.5(Gd1–y
Bi
y
)9Ti18O54 compound (x = 1.5). All substituted Nd compositions exhibit higher permittivities (93–99), lower temperature coefficients of permittivity (11–15 ppm/K) and higher dielectric losses (Q · f = 1300–5500 GHz) than the parent compositions. By exceeding the solid-solubility limit, abrupt changes in the microstructural and dielectric characteristics are induced. 相似文献
14.
The structures of ordered and disordered cubic Ti
x
O
z
= TiO
y
(y= z/x) phases containing both Ti and O vacancies were studied by x-ray diffraction. The results demonstrate that annealing TiO
y
with y= 0.9–1.1 below 1300 K leads to the formation of a monoclinic ordered Ti5O5phase (sp. gr. C2/m(A12m/1)). Symmetry analysis of the monoclinic Ti5O5superstructure indicates that the TiO
y
–Ti5O5ordering transition is defined by the {k
10} Lifshits and {k
4} and {k
1} non-Lifshits wavevector manifolds. The ordering is shown to be a first-order transition accompanied by a decrease in the unit-cell volume of the parent lattice. The Ti and O distribution functions in titanium monoxide are calculated, and the Ti- and O-site near-neighbor environments in the monoclinic Ti5O5superstructure are identified. The region of possible long-range-order parameters is outlined. 相似文献
15.
Y. K. Lee Khin Maung Latt Kim Jaehyung T. Osipowicz Sher-Yi Chiam Kangsoo Lee 《Journal of Materials Science》2000,35(23):5857-5860
Interfacial reactions in Al-0.5%wtCu/Ti/SiO2/Si structure have been investigated up to the annealing temperature of 600°C for 30 min in Argon ambient. Annealing temperature at above 500°C, Al alloy and Ti start to react and produce Al3Ti, which was already reported. Annealing at higher temperatures (550°C, and 600°C) made Al3Ti transformed into Al5Ti2, which is thermodynamically more stable than Al3Ti. The unreacted 52 nm thick Ti which existed underneath of Al5Ti2 might lead to retardation of the reaction between Al5Ti2 and the underlying SiO2. Hence, the formation of ternary compound (Al
x
Ti
y
Si
z
) which is believed to be detrimental to the contact metallization layers was protected. 相似文献
16.
Xu Gaojie Mao Zhiqiang Yan Hongjie Jin Hao Tian Mingliang Zhang Yuheng 《Journal of Superconductivity》1999,12(2):417-420
The normal-state transport properties of La1.85–x
Sr0.15+x
Cu1–x
Al
x
Oy system have been investigated by means of resistivity and thermoelectric power. The structural analysis indicates that with the increase of x, both the lattice parameter a and c decrease. An MI transition appears with Al doping. Al doping partly perturb the periodic potential of the system, thus producing a weakly temperature dependent TEP. The different effect of doping between Al and other transition metal is discussed. 相似文献
17.
E. D. Politova V. V. Ivanova G. M. Kaleva A. V. Mosunov S. G. Prutchenko S. Yu. Stefanovich A. G. Segalla A. L. Kholkin V. V. Shvartsman 《Inorganic Materials》2004,40(9):998-1005
Data are presented on the phase composition, crystal structure, microstructure, and dielectric and piezoelectric properties of (1 – y)[(1 – x)Pb(Mg1/3Nb2/3)O3–xPbTiO3]–yPb(Mg1/2W1/2)O3 (x = 0.30–0.36; y = 0, 0.05, 0.10) ceramics. It is shown that the use of fine-particle magnesia as a starting reagent ensures the formation of single-phase materials. The ceramics with a rhombohedral structure are found to exhibit relaxor behavior. Increasing the content of the Pb(Mg1/2W1/2)O3 perovskite leads to ordering of the domain structure of poled ceramics and increases their piezoelectric charge coefficient d
31 and the width of their phase transitions. 相似文献
18.
M. V. Subbarao Amish G. Joshi Nikesh A. Shah D. G. Kuberkar R. G. Kulkarni 《Journal of Superconductivity》1998,11(6):673-676
The structural and superconducting properties of single-phase La2.5–y
Y0.5Ca1+y
Ba3 (Cu0.88Fe0.12)7O
z
(LYCaBCuFe) (y= 0.0–1.0) compounds with triple perovskite structure are investigated using X-ray diffraction, resistivity, a.c. susceptibility, and oxygen content measurements. Increasing Ca substitution for La resulted in a decrease in unit cell axes and volume. T
c
R=0
shows a marginal increase from 31 K to 37 K for y = 0.0–0.21 and thereafter it decreases with increasing y leading to zero T
c
R=0
at y 0.84. This shows that the suppression of T
c from 80 K to 31 K by Fe doping at x = 0.12 La2.5Y0.5CaBa3(Cu1–x
Fe
x
)7O
z
cannot be compensated by appropriate hole doping with Ca in LaYCaBCuFe. 相似文献
19.
CaO–Al2O3–SiO2 –La2O3–Nd2O3 glass was prepared and their physical properties, such as density, glass transition temperature and crystallization temperature, were measured. The heat treatment of these glasses precipitated Ca2La8(SiO4)6O2 oxyapatite (CLS) crystal for 20CaO–10Al2O3–60SiO2–10La2O3 (mol%) glass and Ca2Nd8(SiO4)6O2 oxyapatite (CNS) crystal was precipitated with Nd2O3 substitution. Crystallization of these glasses was observed at the surface and internally within the samples. The spherical and stick-like crystals were observed throughout the bulk of the glasses and the surface crystal layer of oxyapatite crystals were strongly oriented along the c-axis. The apparent activation energies of crystal growth were estimated as 360 kJ mol–1. 相似文献
20.
L. Barbieri A. Bonamartini Corradi C. Leonelli T. Manfredini G. C. Pellacani 《Journal of Materials Science》1995,30(2):373-380
A family of new glass-ceramic materials, of the general formula (25-x)CaO·xBaO·yMgO· zAl2O3·50SiO2, where x = 1, 2, 5, 10, 15, 20, 25, y = 20 or 14 and z = 5 or 11 (mol%), has been prepared by melting raw materials in two parent glasses and performing heat treatments. The systematic substitution of BaO for CaO in the base glasses allows the effect of feldspars' isomorphism and polymorphism to be studied in a series of glass-ceramics where the structural environment around the bivalent cations, Ca2+ and Ba2+, is systematically altered. Ba2+ has a large effect on the glass transition temperature and dilatometric softening point, causing a decrease with increasing BaO. The crystalline phases have been identified and found to be dependent on the preparation conditions, which are the BaO and Al2O3 contents, the heating rate and the soaking temperature adopted for the crystallization treatments. The infrared spectroscopy technique helped to identify the different polymorphs of barium feldspar, that were not clearly distinguishable by X-ray powder diffractometry due to preferred orientations. The kinetic parameters for the formation of the different crystals have also been determined and correlated with their thermal stability resumed in the well-known time-temperature-transformation curves. 相似文献