共查询到20条相似文献,搜索用时 203 毫秒
1.
对A位掺杂的La1-xSrxFeO3-δ氧化物体系进行了低频内耗测量.研究发现此体系的内耗和模量-温度谱随Sr掺杂量(x)的不同而变化.当Sr含量x=0时,LaFeO3-δ体系的内耗和模量在测量温度范围内(-150—380℃)没有明显变化;而当x=0.2,0.25,1/3以及0.5时,掺杂样品均观察到一个与正交—三角相变对应的相变型内耗峰P1,且其峰温随x增加向低温移动.在x=0.25,1/3,0.5,0.6以及2/3的样品中还观察到一个弛豫型特征的内耗峰P2,此峰伴随着模量的变化,可归于畴壁的运动.进一步分析表明畴壁是受氧空位钉轧的.在x=0.5,0.6以及2/3样品的模量-温度谱上呈现出的模量急剧变化是与三角—立方铁弹性相变有关的.
关键词:
内耗
畴壁
钉扎
铁弹性相变 相似文献
2.
O. M. Fedorova A. M. Jankin L. B. Vedmid G. A. Dorogina I. A. Zvereva 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(8):1159-1160
The mechanisms of formation of NdSr2− x
Ca
x
Mn2O7 (0 ≤ x ≤ 2.0) solid solution have been studied. The dependence of its volume magnetic susceptibility on the calcium concentration
is obtained. The stability of this solid solution is compared with that of similar solid solutions in lanthanum-containing
systems. 相似文献
3.
O. I. Gyrdasova V. N. Krasil’nikov G. V. Bazuev L. Yu. Buldakova M. Yu. Yanchenko 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(8):1113-1116
A original method of synthesis of quasi-one-dimensional Ti1 − x
V
x
(OCH2CH2O)2 (0 ≤ x ≤ 0.13) and Zn1 − x
Co
x
(HCOO)(HOCH2CH2O) (0 ≤ x ≤ 0.3) has been developed. The synthesis products were used as a basis for nanoscale extended Ti1 − x
V
x
O2 and Zn1 − x
Co
x
O oxides. The compounds obtained and products of their thermolysis were investigated by X-ray diffraction, microscopy, IR
spectroscopy, thermogravimetry, and chemical analysis; the shape and size of particles were determined by scanning electron
microscopy. The good prospects of Ti1 − x
V
x
O2 and Zn1 − x
Co
x
O solid solutions as photocatalysts for hydroquinone oxidation are shown. 相似文献
4.
通过对La2-xNdxCuO4+δ(0.1≤x≤1.2)体系中滞弹性弛豫与相变内耗性能的研究发现,当0.1≤x≤1.0时,在250K左右存在一个与间隙氧有关的弛豫内耗峰,并且当0.1≤x≤0.4时,弛豫内耗峰峰高随着x值的增大而升高,此时体系为正交结构;当0.5≤x≤1.0时,体系在宏观上呈现四方结构,此时内耗峰峰高随着x<
关键词:
2-xNd<i>xCuO4+δ')" href="#">La2-xNd<i>xCuO4+δ
间隙氧
弛豫内耗峰
相变内耗峰 相似文献
5.
6.
为研究钆锆烧绿石固化Pu(Ⅳ)的相变化情况及化学稳定性, 以Gd2O3, ZrO2为原料, Ce(Ⅳ)作为Pu(Ⅳ)的模拟替代物质, 采用冷压热烧结的方法制备出Gd2Zr2-xCexO7(0≤ x≤ 2.0)系列样品. 分别在40 °C和70 °C的合成海水中, 对固化体的长期浸出性能进行研究. 借助粉末X射线衍射仪对所制备样品的物相信息进行收集, 利用等离子体质谱仪对固化体的浸出浓度数据进行分析. 研究结果表明: 当x ≤0.08时, 固化体保持为烧绿石相; 当x>0.08时, 固化体转变为具有缺陷的萤石型结构相. 固化体中Gd3+, Zr4+和Ce4+在合成海水中, 随着浸泡时间的延长浸出浓度逐渐上升, 70 °C下的浸出浓度高于40 °C下的浸出浓度. 在42 d时, 固化体中Gd3+的最大浸出浓度在0.032 μg·ml-1以下, Zr4+的最大浸出浓度在0.003 μg·ml-1以下; Ce4+的最大浸出浓度在0.032 μg·ml-1以下. 相似文献
7.
The results of molecular dynamics simulation of the process of atom-by-atom growth of palladium nanoparticles are presented.
The structures obtained for the Pd
n
clusters agree well with the results of the first-principles calculations. The low-symmetry atomic configurations for the
structure of the Pd4 and Pd13 clusters have been obtained using the semiempirical potentials of the interatomic interaction for the first time. 相似文献
8.
9.
采用电弧熔炼法在高纯氩气保护下合成了一系列TbGa1-xGex(0≤x≤0.4)样品. X射线粉末衍射数据表明,样品均为正交晶系的CrB型结构,空间群为Cmcm. TbGa1-xGex化合物的晶格常数随Ge含量的增加而线性减小,TbGa和TbGe赝二元系在0≤x≤0.4范围内形成固溶体. 化合物的顺磁居里温度以及有效磁矩由热磁测量结果确定. 相变温度由交流磁化率的测量获得. 随Ge含量的增加,化合物的相变温度单调下降. 变温X射线粉末衍射实验表明,x=0.2和0.3的样品在110—273K范围内无结构相变.
关键词:
TbGa-TbGe 赝二元系
CrB结构
居里温度
磁化强度 相似文献
10.
I. O. Troyanchuk A. N. Chobot N. V. Tereshko O. S. Mantytskaya E. A. Efimova 《Physics of the Solid State》2011,53(7):1340-1347
The magnetic and magnetotransport properties of Pr0.5Sr0.5Mn1 − x
Co
x
O3 (x ≤ 0.5) solid solutions have been investigated using neutron diffraction methods. The magnetization and electrical conductivity
have been measured in magnetic fields up to 140 kOe. It has been established that, during cooling in the temperature range
from 160 to 110 K, the compounds of compositions with a cobalt content x ≤ 0.07 undergo a structural phase transition from the high-temperature ferromagnetic phase to the antiferromagnetic phase.
A further substitution of cobalt for manganese leads to a stabilization of the inhomogeneous dielectric ferromagnetic state,
whereas a state of the cluster spin-glass type has been revealed in compositions with x = 0.15 and 0.20. At x ≥ 0.25, a new magnetic phase with a Curie temperature up to 210 K is formed as a result of the magnetic interaction between
manganese and cobalt ions. A magnetic phase diagram of the system under investigation has been constructed. 相似文献
11.
Deepika K. S. Rathore N. S. Saxena 《Applied Physics A: Materials Science & Processing》2010,98(2):441-448
Se58Ge42−x
Pb
x
(9≤x≤20) glasses have been prepared using conventional melt quenching technique. Differential Scanning Calorimetric (DSC) measurements
show single glass transition and double crystallization, which indicate the occurrence of phase separation in the samples.
The phases present in the samples were identified using XRD. The kinetics of the glass transition has been studied in terms
of the variation of glass transition temperature with composition and heating rate. In addition to this, activation energy
of the glass transition (E
t
) has also been evaluated and its composition dependence is also investigated. The thermal stability of these glasses has
been investigated using various stability criteria: Deiztal first glass criterion, ΔT, Saad and Poulain weighted thermal stability, H′ and the S-parameter. The values of these parameters were obtained using various characteristic temperatures such as the glass transition
temperature, T
g
, the onset temperature of crystallization, T
c
, and the peak crystallization temperature, T
p
. The values of stability parameters show that the phase corresponding to second crystallization is more stable than the phase
corresponding to first one. The stability in terms of the lead (Pb) content has been determined considering the values of
stability parameters of the phase corresponding to second peak. It was found that the stability increases with the lead content. 相似文献
12.
V. Yu. Topolov 《Physics of the Solid State》2012,54(3):478-484
The specific features of the phase coexistence in crystals of (Bi1 − z
Pb
z
)FeO3 multiferroic solid solutions with a significantly distorted perovskite unit cell below the Curie temperature T
C have been investigated. Some examples of the evolution of the Pm[`3]m = R3cPm\bar 3m = R3c, R3c-C2/m, and R3c-Pbnm heterophase structures and different scenarios of mechanical stress relaxation in the presence of several types of twin domains
of the R3c phase have been analyzed. The Pm[`3]m = R3cPm\bar 3m = R3c heterophase structures in the temperature intervals [T
C-150 K; T
C] (z = 0.025) and [T
C-185 K; T
C] (z = 0.050) have been interpreted. The results have been systematized using the diagrams relating twin structures and phase
boundaries at 0 ≤ z ≤ 0.100. 相似文献
13.
First-principle studies of the geometries and electronic properties of Cum Sin (2≤m+n≤7)clusters 下载免费PDF全文
The equilibrium geometries and electronic properties of CumSin (2 ≤m + n ≤ 7) clusters have been studied by using density functional theory at the B3LYP/6-311+G (d) level. Our results indicate that the structure of CuSin (n 〈6) keeps the frame of the corresponding Sin cluster unchanged, while for CunSi clusters, the rectangular pyramid structure of Cu4Si is shown to be a building block in many structures of larger CunSi clusters. The growth patterns of CumSin clusters become more complicated as the number of Cu atoms increases. Both the binding energies and the fragmentation energies indicate that the Si-Si bond is stronger than the Cu-Si bond, and the latter is stronger than the Cu-Cu bond. Combining the fragmentation energies in the process CumSin →Cu+Cum-l Sin and the second-order difference △2E(m) against the number of Cu atoms of CumSin, we conclude that CumSin clusters with even number of Cu atoms have higher stabilities than those with odd rn. According to frontier orbital analyses, there exists a mixed ionic and covalent bonding picture between Cu and Si atoms, and the Cud orbitals contribute little to the Cu-Si bonding. For a certain cluster size (m + n = 3, 4, 5, 6, 7), the energy gaps of the most stable CumSin clusters show odd-even oscillation with changing m, the clusters with odd m exhibit stronger chemical reactivity than those with even m.[第一段] 相似文献
14.
15.
Yu. N. Zakharov A. A. Pavelko A. G. Lutokhin I. N. Andryushina V. Z. Borodin L. A. Reznichenko 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(8):1125-1127
The influence of thermostating at 450°C on the dielectric and pyroelectric properties of PbZr1 − x
Ti
x
O3 polarized ferroelectric specimens the range 0.02 ≤ x ≤ 0.05 has been investigated. An irreversible increase in the temperature of the ferroelectric-antiferroelectric phase transition
was observed in all specimens upon their cooling after exposure to an elevated temperature for more than 1 h. The original
position of the phase-transition point on the temperature scale was not recovered as a result of afterpoling upon cooling
through the Curie temperature. Heating of the same specimens in the bridged mode up to 650°C with subsequent abrupt immersion
in silicone oil at room temperature (hardening) is accompanied by an additional increase in the range of existence of the
antiferroelectric phase from 3 to 15°C with an increase in the x concentration. 相似文献
16.
We report on a tunneling study of underdoped submicron Bi2Sr2-xLaxCuO6+δ (La-Bi2201) intrinsic Josephson junctions (IJJs), whose self-heating is sufficiently suppressed. The tunneling spectra are measured from 4.2 K up to the pseudogap opening temperature of T* = 260 K. The gap value found from the spectral peak position is about 35 meV and has a weak temperature dependence both below and above the superconducting transition temperature of Tc = 29 K. Since the superconducting gap should have a value of 10-15 meV, our results indicate that the pseudogap (~35 meV) plays an important role in the underdoped La-Bi2201 intrinsic tunneling spectroscopy down to the lowest temperature of 4.2 K. However, the contribution of the superconducting gap can be separated by normalizing the spectra to the one near and above Tc, which shows that the IJJs can be a useful tool for the study of the electronic properties of the La-Bi2201 cuprate superconductors. 相似文献
17.
本文采用基于密度泛函理论的第一性原理全势能线性缀加平面波方法(FLAPW),分析了Bi2Te3-xSex体系中各原子自旋轨道耦合(SOI)的p1/2修正对体系性质的影响,并对Bi2Te3-xSex(x≤3)同晶化合物的电子特性进行系统的理论研究,首次计算出Bi2S
关键词:
2Te3-xSex(x≤3)同晶化合物')" href="#">Bi2Te3-xSex(x≤3)同晶化合物
第一性原理
电子结构
自旋轨道耦合 相似文献
18.
V. S. Rusakov N. I. Chistyakova I. A. Burkovsky A. M. Gapochka T. L. Evstigneeva 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(3):389-393
A M?ssbauer study of the structural and charge states of 57Fe and 119Sn atoms in the compounds of Cu3 −x
Fe
x
SnS4 and Cu2Fe1 − x
Zn
x
SnS4 systems was performed. It was shown that the iron atoms in the compounds of both systems were in the divalent and trivalent
states occupying the tetrahedral positions of the structure. The character of the changes of the degree of covalency of the
Fe2+-S, Fe3+-S and Sn4+-S bonds during the isomorphic substitution in the systems was established. 相似文献
19.
20.
Here we report the synthesis, chemical stability, and electrical conductivity of Ti-doped perovskite-type BaCe0.8-x
Ti
x
Y0.2O3-δ
(x = 0.05, 0.1, 0.2, and 0.3; BCTY). Samples were synthesized by conventional solid state (ceramic) reaction from corresponding
metal salts and oxides at elevated temperature of 1,300–1,500 °C in air. The powder X-ray diffraction confirmed the formation
of a simple cubic perovskite-type structure with a lattice constant of a = 4.374(1), 4.377(1), and 4.332(1) ? for x = 0.05, 0.1, and 0.2 members of BCTY, respectively. Like BaCe0.8Y0.2O3-δ
(BCY), Ti substituted BCTY was found to be chemically not stable in 100% CO2 and form BaCO3 at elevated temperature. The bulk electrical conductivity of BCTY decreased with increasing Ti content and the x = 0.05 member exhibited the highest conductivity of 2.3 × 10−3 S cm−1 at 650 °C in air, while a slight increase in the conductivity, especially at low temperatures (below 600 °C), was observed
in humidified atmospheres. 相似文献