共查询到17条相似文献,搜索用时 140 毫秒
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在-100—200℃温度范围内,测量了(Pb0.97La0.02)(Zr0.65< /sub>Sn0.35-xTix)O3(PZST,0.1≤x≤0.14)反铁电陶 瓷的热膨胀性质.实验结果表明,组分在0.1 ≤x≤0.12的试样室温下为反铁电(AFEt)四方相,热膨胀系数(α)在低温段发生 “弯曲” ,而变温x射线衍射谱(XRD)显示材料保持四方相结构;当Ti含量在0.125≤x≤0.14时,室温 下是铁电三方相(FER),温度升高时FER→AFEt相变体 积收缩,AFEt→立方顺电(PE c)相变体积增大;变温XRD谱证明了材料相结构随温度的转变过程.用多元复杂 化合物存在 纳米线度组分非均匀的观点解释了热膨胀性质随Ti含量演化的物理机理,并得到了该系统的 温度-Ti(x)含量相图.
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热膨胀性质
铁电/反铁电相界
反铁电陶瓷
PZST 相似文献
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利用团簇成分式方法设计系列低密度Co基高温合金[Al-(Co8Ni4)]((Al0.5(Ti/Nb/Ta)0.5Mo0.5)(Mo0.5Cr0.5Co0.5))(=Co8.5Ni4Al1.5Mo1.0Cr0.5(Ti/Nb/Ta)0.5),采用真空非自耗电弧炉制备合金铸锭,并对其在1300℃固溶15h,在900℃下进行长期时效处理,进而对时效态样品进行微观组织表征和力学性能测试.结果表明,当Ti/Nb/Ta,Ti/Nb和Ti/Ta以等物质的量比匹配时,3种合金的微观组织均表现为立方形γ’相均匀地分布在γ基体中,这取决于合金适中的γ/γ’点阵错配度(0.27%—0.34%).在900℃长期时效过程中,3种合金中的γ’相均具有较小的粗化速率,且合金的显微硬度随时效时间基本不发生变化(27... 相似文献
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运用Gaussian 03程序包中的单双迭代三重激发耦合簇理论和相关一致五重基优化了AsH2的基态结构,并在优化结构的基础上计算了它的离解能和振动频率. 结果表明:AsH2基态的平衡构型具有C2v对称性,键长RAs-H=01508 nm,键角∠HAsH=912231°,离解能De(HAs-H)=28795 eV,振动频率ν
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2')" href="#">AsH2
Murrell-Sorbie函数
多体项展式理论
解析势能函数 相似文献
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采用水热法制备了Li4-3xEux(MoO4)2系列红色荧光粉.通过X射线衍射(XRD)、扫描电镜(SEM )和荧光分析(FL)对产物的微结构、形貌和发光性能进行表征分析.XRD分析表明,制备的Li4-3xEux(MoO4)2微晶均为白钨矿四方结构.SEM结果显示:随着x的增大,Li4-3xEux(MoO4)2微晶的晶粒尺寸相应减小,在0.2~0.5 μm之间变化.荧光分析结果表明:源于Eu3+的5D0→7F2和5D0→7F1电荷转移的592 nm和614 nm的特征发射峰显现明显,后者的发射强度远远大于前者.随着x的增大,样品中Eu3+的两个特征发射峰的强度先增大后减小,在x=1.0时达到最大. 相似文献
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Ion channeling measurements have been performed on KTaO3:Nb (KTN) in order to check the position of Nb relative to the tantalum site. No evidence for “off-center” Nb was found in the limit of experimental accuracy. In addition, the carbon content of the samples was measured and large concentrations were found (?300 p.p.m. weight). Possible relationship between Nb location and carbon presence is discussed. 相似文献
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A model of cooperative behaviour for K 1 m x Li x Ta 1 m y Nb y O 3 (KLTN) and for other disordered systems like ferroelectric relaxors is considered from the point of view of contribution of infinite-range dipole-dipole interactions. It is shown that a local piezoeffect for off-center impurities in crystals with rather high electrostriction is responsible as origin of a infinite-range electric dipole-dipole interaction via elastic fields as well as for a co-existence of ferroelectric and glass-like states with reentrant glass effect. 相似文献
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本文用中子飞行时间方法对C-15相的超导材料V2Hf,V2Ta和V2Hf0.8Ta0.2以及V2Zr0.5。Hf0.5和V2Zr0.5Hf0.33Ta0.17的热中子非弹性散射谱作了测量,并计算出相对的广义声子态密度。结果与早先发表的Nb对C-15相V2Zr和V2(Hf0.5Zr0.5)系列声子性能的影响一致:声子频率随超导转变温度Tc增加而软化,随Tc减小而硬化。这表明,对于此类材料弹性软化在一定程度上对提高Tc起了作用。结果还进一步表明V2Zr或V2Hf与V2(Zr0.5Hf0.5)之间有着质的差别,V2Hf加Ta后,Tc增加,声子频率软化,而V2(Zr0.5Hf0.5)加Ta后,Tc减小,声子频率则略有硬化。这与V2Zr和V2(Hf0.5Zr0.5)加Nb的结果是一致的。此结果可以用角动量分波表象的能带论方法分析电-声耦合相互作用得出的杂化理论来定性解释。
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Jiagang Wu Jiliang Zhu Dingquan Xiao Jianguo Zhu Junzhe Tan Qinglei Zhang Yuanyu Wang 《Applied Surface Science》2007,253(14):6222-6225
(Pb0.95Ca0.05)(Nb0.02Zr0.80Ti0.20)O3 [PCNZT] thin films were deposited on the Pt(1 1 1)/Ti/SiO2/Si(1 0 0) substrates by RF magnetron sputtering with and without a LaNiO3 [LNO] buffer layer. Ca and Nb elements in PZT films enhance the ferroelectric property, LaNiO3 buffer layer improves the crystal quality of the PCNZT thin films. PCNZT thin films possess better ferroelectric property than that of PZT films for Ca and Nb ion substitution, moreover, PCNZT thin films with a LNO buffer layer possess (1 0 0) orientation and good ferroelectric properties with high remnant polarization (Pr = 38.1 μC/cm2), and low coercive field (Ec = 65 kV/cm), which is also better than that of PCNZT thin films without a LNO buffer layer (Pr = 27.9 μC/cm2, Ec = 74 kV/cm). The result shows that enhanced ferroelectric property of PZT films can be obtained by ion substitution and buffer layer. 相似文献
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采用基于密度泛函理论的广义梯度近似方法和赝势平面波法,对多铁材料BiFeO3的铁电反铁磁相和可能的高温顺电相的电子结构进行了第一性原理研究.计算验证了BiFeO3基态为G型反铁磁有序,Fe离子的理论磁矩与实验值相符.铁电相变发生后,Bi-6s态和6p态发生了电荷转移,Bi-6s电子的作用更加明显.Born有效电荷的研究表明铁电畸变主要表现为Bi原子的位移,并且电极化强度计算值很好地符合薄膜实验结果.部分态密度的计算表明Bi-6p态的成键轨道与反键轨道间的能量劈裂
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第一性原理
铁电性
铁电畸变
反铁磁性 相似文献
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ABSTRACTThe results of low-temperature linear and nonlinear susceptibilities, polarization measurements and the dc electric field dependence of the dielectric properties of the lithium-doped potassium tantalate K1-xLixTaO3, x = 0.034 (KLT-3.4%Li) solid solution are presented. The coexistence of the relaxor-like and ferroelectric behavior and different mechanisms leading to either of them are discussed. The observed ferroelectric phase transition is of the first-order type with temperature hysteresis. This transition is due to the off-center motions of Ta ions in the octahedral environment of oxygen ions. Clusters of Li+ ions produce a relaxor-like behavior and random electric field. This field reduces the depolarization field and allows off-center motions of Ta ions and an appearance of spontaneous polarization. 相似文献
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V.A. Trepakov S.A. Prosandeev P. Galinetto S.E. Kapphan L.A. Boatner 《Journal of Physics and Chemistry of Solids》2004,65(7):1317-1327
An unusual sequence of phase transitions (PT) and reentrant dipole glass-like phase formation at low temperatures was found recently in KTaO3 weakly doped with Li and Nb (K0.9986Li0.0014Ta0.976Nb0.024O3) [Phys. Rev. B 63 (2001) 172]. We report on detailed low frequency (100 Hz-1 MHz) permittivity and Raman light scattering studies of similar composition, but without Li admixture, KTa1−xNbxO3 with x=0.018 (KTN1.8). The aim of the study is to answer the question if the reentrant dipole glass-like phase exists in KTN1.8 and what is the microscopic origin of this phase. A detailed study of the sharp low-temperature PT observed at TC∼27 K revealed properties inherent to the reentrant glass-type state at lower temperatures. The substitution of Nb for Ta influences the TO1 soft lattice mode and leads to PT with the long-range ferroelectric ordering. A crossover to an order-disorder polar microregion dynamics with a non-standard ε′(T) behaviour and dipole glass-like formation were found below TC (at ∼15 K), which is attributed to the randomness of the Nb distribution. A crossover to the long-range order was found under a dc bias field. 相似文献