共查询到19条相似文献,搜索用时 31 毫秒
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制备了Bi7Ti4NbO21,Bi4Ti3O12及Nb掺杂Bi4Ti3O12(Nb-Bi4Ti3O12)层状结构铁电陶瓷材料.结合Nb-Bi 4Ti3O12的介电温谱和 退极化实验结果,研究了Bi7Ti4NbO21的晶体结构 对其介电、压电性能的影响 .高分辨透射电镜结果表明,在Bi7Ti4NbO21中, 沿着c轴方向,(Bi2Ti3O10)2-和(BiTiNbO7)2-两个类钙钛矿层分别 与(Bi2O2)2+层叠加堆积而成.这种晶体结构决定了Bi7Ti4NbO21的 介电温谱在668℃和845℃出现介 电双峰.结合极化样品的退化实验分析,说明材料在这两个温度附近发生了铁电—铁电相变 、铁电—顺电相变,分别是(Bi2Ti3O10)2-< /sup>和(BiTiNbO7)2-层状 结构发生微观结构相变的结果.在退极化过程中,由于受热时钙钛矿层内空位引起的缺陷偶 极子的定向排列受到破坏,引起材料部分退极化,表现为300℃热处理后Bi7Ti 4NbO 21的压电活性降低了10%,显示了室温下材料的压电性能来源于自发极化的固有电 偶极子和缺陷偶极子的共同贡献. 相似文献
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首次采用高压高温方法合成了Sr2SiO4:Er3+Bi3+和SrSiO3:Er3+Bi3+发光材料,研究了合成压力、合成温度对发光特性的影响。与常压合成产物相比较,发光谱发生了红移;谱线半宽度显著增大;发光强度和量子发光效率下降。X射线衍射分析得出,SrSiO3:Er3+Bi3+发生了结构相变,Sr2SiO4:Er3+Bi3+结构未变但晶格参数发生了变化,且主衍射峰强度发生了反转。分析表明,发光特性的变化是压致晶场、库仑及自旋-轨道相互作用的变化引起的。 相似文献
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采用金刚石对顶砧高压装置,在室温下对正辛烷(C8H18)进行了原位高压拉曼光谱研究,实验的最高压力为13GPa。在实验的压力范围内,正辛烷的拉曼峰位随压力的升高均向高频移动,峰强逐渐减弱,峰形变宽。常态为液态的正辛烷在0.8 GPa时,拉曼频移随压力的变化曲线出现了拐点,发生了液-固相变;在6.8 GPa时,伴随着原拉曼峰的消失或劈裂,以及新拉曼峰的出现,此时正辛烷可能发生了固-固相变。该相变压力低于已有的低碳数正烃烷的压致相变结果。正烃烷的压致相变压力点,具有随着结构链长的增加,其相变压力降低的规律。 相似文献
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利用溶胶-凝胶法在Pt/Ti/SiO2/Si(100)衬底上制备了Nd掺杂Bi4Ti3O12(Bi4-xNdxTi3O12, x=0.00,0.30,0.45,0.75,0.85,1.00,1.50)铁电薄膜样品.研究了Nd掺杂对Bi4Ti3O12薄膜的微结构和铁电性能的影响.研究结果表明:Nd掺杂未改变Bi4Ti3O12薄膜的基本晶体结构.在掺杂量x<0.45时,Nd3+只取代类钙钛矿层中的A位Bi3+.当x=0.45时,样品剩余极化强度达最大值,在270kV·cm-1的电场下为32.7μC·cm-2.掺杂量进一步增加时,结构无序度开始明显增大,Nd3+开始进入(Bi2O2)2+层,削弱其绝缘层和空间电荷库的作用,导致材料剩余极化逐渐下降.当掺杂量x达到1.50时,掺杂离子最终破坏(Bi2O2)2+层的结构,材料发生铁电-顺电相变. 相似文献
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本文合成了系列Bi2Ti4-xTexO11样品,拉曼光谱及X射线衍射谱表明该体系的相转化边界发生在x=0.5处,Bi2Te4O11的压致结构相变的压力为8.2GPa。本文结果证实了我们过去对Bi2Ti4O11相变提出的机制 相似文献
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Phase Transition Kinetics in Bi3NbO7 Evaluated by in situ Isothermal Conductivity Measurements
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Kinetics of phase transformation from pseudocubic to tetragonal phase in Bi3NbO7 solid solution is studied by using the ac impedance method under isothermal conditions. Conductivity of the investigated compound is used to characterize the kinetic process of the transition. The Avrami exponent and the activation energy of phase transition are around 1.5 and 3.5eV, respectively. These kinetic parameters reveal that the pseudocubic-tetragonal transition in Bi3NbO7 .belongs to a three-dimensional diffusion-controlled growth with zero nucleation rate. 相似文献
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Technical Physics - Single-crystal Bi4Ti3O12 films deposited on a 4-nm-thick Ba0.4Sr0.6TiO3 sublayer covering an MgO(001) substrate have been investigated. It has been found that the unit cells of... 相似文献
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The measurements of the absolute values of the thermopower and of the relative electrical resistance have been performed for n type Bi2Te3 under hydrostatic pressure up to 9 GPa at room temperature. Under pressures exceeding 5 GPa and up to the phase transition (at 7 GPa), the samples with the charge carrier density below 10?19 cm?3 exhibit an anomalous growth of the thermopower. For the purest sample (n = 10?18 cm?3), the thermopower is as high as +150 μV/K. The pressure dependence of the electrical resistance for n-Bi2Te3 does not exhibit any anomalies up to the pressure corresponding to the phase transition (7 GPa). Thus, the state with the giant thermoelectric efficiency is found in Bi2Te3 under pressure before the phase transition. 相似文献
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In situ angle dispersive synchrotron X-ray diffraction and Raman scattering measurements under pressure are em- ployed to study the structural evolution of Cu4Bi4S9 nanoribbons, which are fabricated by using a facile solvothermal method. Both experiments show that a structural phase transition occurs near 14.5 GPa, and there is a pressure-induced re- versible amorphization at about 25.6 GPa. The electrical transport property of a single Cu4Bi4S9 nanoribbon under different pressures is also investigated. 相似文献
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Raman spectroscopy investigation on the pressure-induced structural and magnetic phase transition in two-dimensional antiferromagnet FePS3
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The layered van der Waals antiferromagnetic FePS3 has received considerable attention because long range magnetic ordering can remain with single atoms layer, which offers potential applications in future ultrathin devices. Here, we perform Raman spectroscopy to systematically explore the variations of lattice vibration and crystal structure under pressure up to 18.9 GPa. We observe two structural phase transitions at approximately 4 GPa and 13 GPa, respectively. Moreover, by monitoring spin-related Raman modes, we demonstrate a pressure-induced magnetic structure transition above 2 GPa. These modes disappear accompanying the second structural phase transition and insulator-to-metal transition (IMT), indicating the suppression of long-range magnetic ordering, in agreement with earlier neutron powder diffraction experiments. 相似文献
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采用氧化固相法制备了(1-x)(Bi0.5Na0.5)TiO3-xBa(Ti0.95Zr0.05)O3(BNT-BZT)陶瓷,其中掺入量x的值分别为0,0.04,0.05,0.06,0.07.研究了BNT-BZT体系陶瓷的准同型相界以及陶瓷材料的微观结构和性能之间的关系,并探讨了陶瓷的介电性能和铁电等性能.通过探究Ba(Ti,Zr)O3(BZT)掺杂量对BNT 各性能的影响得出了当掺杂量x=0.05得到结构较为致密,介电,铁电性能较好的样本,对工业化研究和生产有重要的意义 相似文献