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1.
New solid solutions, Bi2?x?y Tm x Nb y O3+δ, with tetragonal and cubic structures have been synthesized in the Bi2O3-Tm2O3-Nb2O5 system, and their electrical conductivity has been measured at temperatures from 670 to 1020 K. The 1020-K conductivity of the tetragonal solid solution Bi1.8Tm0.15Nb0.05O3+δ is comparable to that of Bi1.75Tm0.25O3, the best conductor in the Bi2O3-Tm2O3 system. 相似文献
2.
The electrical resistivity of Nb2O5-NiO materials was measured in the range 20-500°C. The resistivity of the samples was found to be sensitive to the presence of ammonia or sulfur dioxide in air. Some of the oxides in the Nb2O5-NiO system are potentially attractive as materials for temperature and gas sensors. 相似文献
3.
Yao Ying Lichao Wang Wangchang Li Liang Qiao Jingwu Zheng Jing Yu Wei Cai Liqiang Jiang Shenglei Che Lei Zhang Langsheng Ling 《Journal of Superconductivity and Novel Magnetism》2018,31(11):3553-3558
We investigated the magnetic properties of a geometrically frustrated magnet of ZnFe2O4 nanoparticles by carrying out the comprehensive measurements of dc magnetization and ac susceptibility. Spin glass is confirmed to occur in this weakly Fe(Zn)-ionic-inversed sample. The common characteristics of spin glass including the aging, the memory, and the rejuvenation effects were observed. By using the critical-power law to study the spin dynamics, the spin-glass transition temperature Tg is obtained to be 18 K and the dynamic exponent zν is 8.0. The weak exchange interaction disorder introduced by the ferrimagnetic JAB interaction, together with the weak nonmagnetic dilute disorder induced by the ionic inversion, is responsible for the formation of spin glass in the ZnFe2O4 nanoparticles. 相似文献
4.
E. Mehran Saber Farjami Shayesteh F. Nasehnia 《Journal of Superconductivity and Novel Magnetism》2016,29(5):1241-1247
We study structural and magnetic properties of magnetic ceramic Co x Zn1?x Fe2O4 nanoparticles synthesized by the co-precipitation method and optimize its size and magnetic property for possible application in wastewater treatment. The effects of long stirring time under boiling condition and the introduction of the third metal ion to the structure are investigated. To study the microstructural and magnetic characteristic of the samples, X-ray diffraction (XRD), vibrating sample magnetometer (VSM), Fourier transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM) analyses are carried out. The diffracted peaks of XRD pattern confirm the formation of spinel phase. In addition, we study the effect of Co doping on the peak positions in the spinel structures. To evaluate crystallite size and other lattice parameters of the samples, we use the Rietveld method as a nearly exact approximation instead of Scherrer formula. Thus, the Rietveld refinement method has been utilized and structural and lattice parameters of the samples are extracted using Reflex program. In contrast with other works, our nanoparticles show superparamagnetic behavior, larger surface area, and better crystallinity with no calcination which originates from the condition of the synthesis method. 相似文献
5.
LiMn2-x
ErxO4 (x ≤ 0.02) materials were synthesized by a rheological phase reaction method. The thermal behavior of the materials was examined by thermogravimetric and differential scanning calorimetry. X-ray diffraction showed that the samples (x ≤ 0.02 ) exhibited the same phase as the pure spinel. The lattice parameter of the Er-doped spinel was smaller than that of the undoped one and decreased with increasing doping level. Cyclic voltammograms showed two reversible processes corresponding to the typical response of spinel LiMn2O4 and revealed an insertion-extraction reaction occurring at two stages in the 4-V region. The electrochemical performances of the samples were studied and displayed a better reversibility and cyclability.__________From Neorganicheskie Materialy, Vol. 41, No. 6, 2005, pp. 740–743.Original English Text Copyright © 2005 by Haowen Liu, Li Song, Kelli Zhang.This article was submitted by the authors in English. 相似文献
6.
The electrical properties of layered perovskite-like compounds with the general formula Bi
m + 1Fe
m − 3Ti3O3m + 3 have been studied in relation to their physicochemical properties and structure. 相似文献
7.
Semiconducting glasses of the Fe2O3-Bi2O3-K2B4O7 system were prepared by the press-quenching method and their dc conductivity in the temperature range 223–393 K was measured. The glass transition temperature values (Tg) of the present glasses were larger than those of tellurite glasses. This indicates a higher thermal stability of the glass in the present system. The density for these glasses was consistent with the ionic size, atomic weight and amount of different elements in the glasses. Mössbauer results revealed that the relative fraction of Fe increases with increasing Fe2O3 content. Electrical conductivity showed a similar composition dependency as the fraction of Fe. The glasses had conductivities ranging from 10 to 10 Scm at temperatures from 223 to 393 K. Electrical conduction of the glasses was confirmed to be due to non-adiabatic small polaron hopping and the conduction was primarily determined by hopping carrier mobility. 相似文献
8.
Platelike Li1 ? x Na x Cu2O2 single crystals up to 2 × 10 × 10 mm in dimensions have been grown by slowly cooling (1 ? x)Li2CO3·xNa2O2·4CuO melts in alundum crucibles in air. Li1 ? x Na x Cu2O2 solid solutions in the LiCu2O2-NaCu2O2 system have been shown to exist in the composition range 0.78 < x < 1. The temperature stability ranges of NaCu2O2 and LiCu2O2 are 780–930 and 890–1050°C, respectively. The Mössbauer spectra and electrical conductivity of the crystals have been measured. 相似文献
9.
The thermoelectric power and d.c electrical conductivity of x V2O5⋅40CaO⋅(60−x)P2O5 (10 ≤ x ≤ 30) glasses were measured. The Seebeck coefficient (Q) varied from +88 μ V K−1 to −93 μV K−1 as a function of V2O5 mol%. Glasses with 10 and 15 mol% V2O5 exhibited p-type conduction and glasses with 25 and 30 mol% V2O5 exhibited n-type conduction. The majority charge carrier reversal occurred at x = 20 mol% V2O5. The variation of Q was interpreted in terms of the variation in vanadium ion ratio (V5 +/V4 +). d.c electrical conduction in x V2O5⋅40CaO⋅(60−x)P2O5 (10 ≤ x ≤ 30) glasses was studied in the temperature range of 150 to 480 K. All the glass compositions exhibited a cross over from
small polaron hopping (SPH) to variable range hopping (VRH) conduction mechanism. Mott parameter analysis of the low temperature
data gave values for the density of states at Fermi level N (EF) between 1.7 × 1026 and 3.9 × 1026 m−3 eV−1 at 230 K and hopping distance for VRH (RVRH) between 3.8 × 10−9m to 3.4 × 10−9 m. The disorder energy was found to vary between 0.02 and 0.03 eV. N (EF) and RVRH exhibit an interesting composition dependence. 相似文献
10.
V. M. Chumarev V. P. Mar’evich A. V. Larionov A. Ya. Dubrovskii 《Inorganic Materials》2011,47(3):267-272
Reactions of vanadium, niobium, and tantalum pentoxides with aluminum nitride have been studied using X-ray diffraction. At
temperatures from 1000 to 1600°C, we have identified various V, Nb, and Ta nitrides. The composition of the niobium and tantalum
nitrides depends on the reaction temperature. The tendency toward nitride formation becomes stronger in the order V2O5 < Ta2O5 < Nb2O5. 相似文献
11.
T. Joseph S. Uma J. Philip M. T. Sebastian 《Journal of Materials Science: Materials in Electronics》2011,22(8):1000-1009
A new polymer-ceramic composite was prepared using PTFE and low loss Sr2ZnSi2O7. The dielectric properties of the composite were studied in the microwave and radiofrequency ranges. The relative permittivity
(εr) and dielectric loss (tan δ) increased with the filler loading from 0.10 to 0.50 volume fractions (vf). The observed values of εr, thermal conductivity and coefficient of thermal expansion (CTE) were compared with the corresponding theoretical predictions.
The ability of the composite towards moisture absorption resistance was studied as a function of filler loading. It was also
found that the variation of εr was less than 2% in the temperature range 25–90 °C, at 1 MHz. For a filler content of 0.50 vf, the PTFE/Sr2ZnSi2O7 composite exhibited εr = 4.4, tan δ = 0.003 (at 4–6 GHz), CTE = 38.3 ppm/°C, thermal conductivity = 2.1 W/mK and moisture absorption = 0.09 wt%. 相似文献
12.
V. N. Skrobot V. L. Ugolkov R. G. Grebenshchikov V. V. Gusarov 《Inorganic Materials》2005,41(8):840-844
The Dy2O3-Rh2O3 system is studied by thermal analysis, x-ray diffraction, and chemical analysis of annealed and quenched samples. The results are used to construct a schematic subsolidus phase diagram of the system. Only one double oxide, DyRhO3, is obtained. Some of its physicochemical properties are reported.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 8, 2005, pp. 960–965.Original Russian Text Copyright © 2005 by Skrobot, Ugolkov, Grebenshchikov, Gusarov. 相似文献
13.
A procedure has been developed for the synthesis of MgAl2O4 nanopowders with a characteristic particle size of 10–40 nm. Translucent hydrous xerogels have been synthesized as precursors
to MgAl2O4. The synthesized magnesium aluminum spinel nanopowders are promising for the fabrication of optical ceramics. 相似文献
14.
Liang Fang Zhao Yang Hui Zhang Chunchun Li Xiyang Peng Changzheng Hu Dongjin Chu 《Journal of Materials Science: Materials in Electronics》2011,22(9):1208-1212
Polycrystalline samples of Ba4Ln2Fe2Ta8O30 (Ln = La and Nd) were prepared by a high temperature solid-state reaction technique. The formation, structure, dielectric
and ferroelectric properties of the compounds were studied. Both compounds are found to be paraelectrics with filled tetragonal
tungsten bronze (TB) structure at room temperature. Dielectric measurements revealed that the present ceramics have exceptional
temperature stability, a relatively small temperature coefficient of dielectric constant (τ
ε
) of −25 and −58 ppm/°C, with a high dielectric constant of 118 and 96 together with a low dielectric loss of 1.2 × 10−3 and 2.8 × 10−3 (at 1 MHz) for Ba4La2Fe2Ta8O30 and Ba4Nd2Fe2Ta8O30, respectively. The measured dielectric properties indicate that both materials are possible candidates for the fabrication
of discrete multilayer capacitors in microelectronic technology. 相似文献
15.
Mohamed M. Gomaa Hussein Darwish Saad M. Salman 《Journal of Materials Science: Materials in Electronics》2008,19(1):5-15
The ac electrical properties of some lithium silicate glasses and glass-ceramics containing varying proportions of Y2O3 and/or Fe2O3 were measured to investigate their electronic hopping mechanism. There is a clear variation of these properties with composition.
The obtained results were related to the concentration and role of Y2O3 and/or Fe2O3 in the lithium silicate glass structure. In crystalline solids the electrical properties data obtained were correlated to
the type and content of the mineral phases formed as indicated by X-ray diffraction analysis (XRD).
The conductivity, dielectric constant and dielectric loss of the studied glasses were studied using the frequency response
in the interval 30 Hz–100 KHz and the effect of compositional changes on the measured properties was investigated. The measurements
revealed that the electrical responses of the samples were different and complex. The addition of Y2O3 generally, decreased the ac conductivity, dielectric constant and dielectric losses of the lithium silicate glasses. The
addition of Fe2O3 in Y2O3-containing glasses increases the conductivity, while, the dielectric constant and dielectric losses were found to be decreased.
However, the addition of Fe2O3 instead of Y2O3 led to decrease the ac conductivity and increased their dielectric constant and dielectric losses.
The obtained data were argued to the internal structure of the lithium silicate glass and the nature or role-played by weakness
or rigidity of the structure of the sample.
Lithium disilicate-Li2Si2O5, lithium metasilicate-Li2SiO3, two forms of yttrium silicate Y2Si2O7 & Y2SiO5, iron yttrium oxide-YFeO3, lithium iron silicate-LiFeSi2O6 and α-quartz phases were mostly developed in the crystallized glasses.
The conductivity of the crystalline materials was found to be relatively lower than those of the glass. At low frequency,
as the Y2O3 content increased the ac conductivity, dielectric constant and dielectric loss data of the glass-ceramics decreased. However,
the addition of Fe2O3 to the Y2O3 containing glass-ceramic led to increase the conductivity. The addition of high content of Fe2O3 instead of Y2O3 in the glass ceramic led to increase the ac conductivity. 相似文献
16.
Single-crystal and polycrystalline samples of Sc4Ti3O12 have been shown to contain nanodomains (10–50 nm) with different degrees of ordering, coherent with the fluorite-like matrix. The oxygen-ion conductivity of this compound has been determined in the range 300–1000°C in air using impedance spectroscopy. The nanostructured single-crystal and polycrystalline samples are close in the activation energy for bulk conduction at both low and high temperatures: ?1.26 and 1.29 eV in the range 300–775°C, ?1.98 and 2.07 eV in the range 775–1000°C. 相似文献
17.
N. A. Gorodylova V. N. Baumer I. V. Zatovsky A. A. Babarik N. S. Slobodyanik O. V. Shishkin 《Inorganic Materials》2011,47(2):156-162
We have studied general trends of crystallization from high-temperature solutions in the K2O-P2O5-V2O5-Bi2O3 system at P/V = 0.5?2.0, K/(P + V) = 0.7?1.4, and Bi2O3 contents from 25 to 50 wt % and identified the stability regions of BiPO4, K3Bi5(PO4)6, K2Bi3O(PO4)3, and K3Bi2(PO4)3 ? x (VO4) x (x = 0?3) solid solutions. The synthesized compounds have been characterized by X-ray powder diffraction and IR spectroscopy, and the structure of two solid solutions has been determined by single-crystal X-ray diffraction (sp. gr. C 2/c): K3Bi2(PO4)2(VO4), a = 13.8857(8), b = 13.5432(5), c = 6.8679(4) Å, β = 114.031(7)°; K3Bi2(PO4)1.25(VO4)1.75, a = 13.907(4), b = 13.615(2), c = 6.956(2) Å, β = 113.52(4)°. 相似文献
18.
Y2O3 + Nd2O3 co-stabilized ZrO2-based composites with 40 vol% WC were fully densified by pulsed electric current sintering (PECS) at 1350 °C and 1450 °C.
The influence of the PECS temperature and Nd2O3 co-stabilizer content on the densification, hardness, fracture toughness and bending strength of the composites was investigated.
The best combination of properties was obtained for a 1 mol% Y2O3 and 0.75 mol% Nd2O3 co-stabilized composite densified for 2 min at 1450 °C under a pressure of 62 MPa, resulting in a hardness of 15.5 ± 0.2
GPa, an excellent toughness of 9.6 ± 0.4 MPa.m0.5 and an impressive 3-point bending strength of 2.04 ± 0.08 GPa. The hydrothermal stability of the 1 mol% Y2O3 + 1 mol% Nd2O3 co-stabilized ZrO2-WC (60/40) composites was compared with that of the equivalent 2 mol% Y2O3 stabilized ceramic. The double stabilized composite did not degrade in 1.5 MPa steam at 200 °C after 4000 min, whereas the
yttria stabilized composite degraded after less than 2000 min. Moreover, the (1Y,1Nd) ZrO2-WC composites have a substantially higher toughness (~9 MPa.m0.5) than their 2Y stabilized equivalents (~7 MPa.m0.5). 相似文献
19.
We gave studied the crystallization behavior of 30BaO · 25Bi2O3 · 45B2O3 glasses doped with Eu2O3 to different levels. At a Eu2O3 content of 7 mol % or higher, the glasses undergo volume crystallization. The only precipitating phase is a solid solution
between europium and bismuth oxides. With increasing europium concentration in the glass, the structure of the crystallites
changes from cubic to rhombohedral. We have investigated the morphology, physicochemical properties, and luminescence spectra
of the glasses and glass-ceramics. 相似文献
20.
L. A. Trusov D. D. Zaitsev P. E. Kazin Yu. D. Tret’yakov M. Jansen 《Inorganic Materials》2009,45(6):689-693
Glasses with nominal compositions 11SrO · 5.5Fe2O3 · 4.5Al2O3 · 4B2O3 (1) and 15SrO · 5.5Fe2O3 · 4.5Al2O3 · 4B2O3 (2) were prepared by rapidly quenching oxide melts between counterrotating steel rollers. The glasses were then heat-treated in the range 650–950°C to produce glass-ceramic samples. The samples were characterized by X-ray diffraction, electron microscopy, and magnetic measurements. The phase composition of the glass-ceramics was determined, and their microstructure and magnetic properties were studied. The annealing temperature was shown to have a strong effect on the coercivity of the materials, which reaches 650 and 570 kA/m for compositions 1 and 2, respectively. 相似文献