溶胶-凝胶法制备Sr2Bi4Ti5O18薄膜及其铁电性能研究

采用溶胶-凝胶法,在氧气氛中和层层晶化的工艺条件下,成功地制备了沉积在Pt/Ti/SiO2/Si(100)衬底上的铁电性能优良的Sr2Bi4Ti5O18(SBTi)薄膜,并研究了SBTi薄膜的微结构、表面形貌、铁电性能和疲劳特性.研究表明:薄膜具有单一的层状钙钛矿结构,且为随机取向;薄膜表面光滑,无裂纹,厚度约为725nm;铁电性能测试显示较饱和、方形的电滞回线,当外电场强度为275kV/cm时,其剩余极化2Pr和矫顽场2Ec分别为24.0μC/cm2和137.8kV/cm;疲劳测试发现薄膜经过4.4×1010次极化反转后,基本没有显示疲劳.     

溶胶-凝胶法制备Sr2Bi4Ti5O18薄膜及其铁电性能研究

采用溶胶-凝胶法,在氧气氛中和层层晶化的工艺条件下,成功地制备了沉积在Pt/Ti/SiO₂/Si(100)衬底上的铁电性能优良的Sr₂Bi₄Ti₅O₁₈ (SBTi)薄膜,并研究了SBTi薄膜的微结构、表面形貌、铁电性能和疲劳特性.研究表明：薄膜具有单一的层状钙钛矿结构，且为随机取向；薄膜表面光滑，无裂纹，厚度约为725nm；铁电性能测试显示较饱和、方形的电滞回线，当外电场强度为275kV/cm时 关键词： 溶胶-凝胶法 铁电薄膜 2Bi₄Ti₅O₁₈')" href="#">Sr₂Bi₄Ti₅O₁₈     

(Bi,La)4Ti3O12-Sr(Bi,La)4Ti4O15共生结构铁电材料性能研究

采用固相烧结工艺，制备了不同La掺杂量(x=0.00，0.25，0.50，0.75，1.00，1.25和1.50) 的(Bi, La)₄Ti₃O₁₂-Sr(Bi, La)₄Ti4O₁₅ (SrBi_8-xLa_xT i₇O₂₇)共生结构铁电陶瓷样品.用x射线衍射对其进行微结构分析 ，并测量铁 关键词： 4Ti₃O₁₂-SrBi₄Ti₄O₁₅')" href="#">Bi₄Ti₃O₁₂-SrBi₄Ti_{4O15 La掺杂 铁电性能 居里温度 弛豫铁电}     

Multiferroic properties of solben gel derived Bi5Fe1-xCoxTi3O15 thin films

Co-doped Bi₅FeTi₃O₁₅ thin films (BFCT-x, Bi₅Fe_1-xCo_xTi₃O₁₅) were prepared using a sol—gel technique. XRD patterns confirm their single phase Aurivillius structure, and the corresponding powder Rietveld analysis indicates the change of space group around x=0.12. The magnetic hysteresis loops are obtained and ferromagnetism is therefore confirmed in BFCT-x thin films. The remanent magnetization (M_r) first increases and reaches the maximum value of 0.42 emu/cm³ at x=0.12 due to the possible Fe³⁺—O—Co³⁺ ferromagnetic coupling. When x = 0.25, the M_r increases again because of the dominant Fe³⁺—O—Co³⁺ ferromagnetic coupling. The remanent polarization (2P_r) of BFCT-0.25 was measured to be as high as 62 μC/cm², a 75% increase when compared with the non-doped BFCT-0 films. The 2P_r remains almost unchanged after being subjected to 5.2 × 10⁹ read/write cycles. Greatly enhanced ferroelectric properties are considered to be associated with decreased leakage current density.     

Relaxation of Dielectric Loss Peak over Intermediate Temperature Range in Bi5TiNbWO15 Intergrowth

A dielectric loss peak with relaxation-type characteristic is observed in Bi5TiNbWO15 over 200-400℃. The modified Cole-Cole relation by introducing relaxation strength as another important fitting parameter is used to describe this temperature-dependent behaviour of dielectric relaxation process. This peak is considered to be associated with the oxygen vacancies inside the grains and with its activation energy by relaxation determined to be 0.76eV. The obtained broadening factor α is around 0.4, which indicates a strong correlation between those relaxation units. It is confirmed that the behaviour of this peak is due to the combined effects of the dielectric relaxation and electrical conduction by the thermal motion of oxygen vacancies. These results axe further confirmed in Bi5TiNbWO15 samples through oxidization atmosphere treatment and Nd modification respectively.     

The doping effects of BiFe1-xCoxO3 (x=0.0-0.8) in layered perovskite Bi4Ti3O12 ceramics

Bi5Fe1-xCoxTi3O15(x = 0.0, 0.2, 0.4, 0.5, 0.6, and 0.8) multiferroic ceramics are synthesized in two steps using the solid state reaction technique. X-ray diffraction patterns show that the samples have four-layer Aurivillius phases. At room temperature (RT), the samples each present a remarkable coexistence of ferromagnetism (FM) and ferroelectricity (FE). The remnant polarization (2P r ) reaches its greatest value of 14 μC/cm 2 at x = 0.6. Remnant magnetization (2M r ) first increases and then decreases, and the greatest 2M r is 7.8 menu/g when x = 0.5. The magnetic properties for x = 0.4 are similar to those for x = 0.6, indicating that the magnetic properties originate mainly from the coupling between Fe 3+ and Co 3+ ions, rather than from their own magnetic moments.     

La掺杂诱发层状钙钛矿型铁电体弛豫性相变的介电研究

制备了La掺杂层状钙钛矿铁电体材料SrBi₄Ti₄O₁₅, Sr₂Bi₄Ti₅O₁₈以及共生结构Bi₄Ti₃O₁₂-SrBi₄Ti₄O₁₅，通过研究样品的变温介电特性发现，SrBi_4-xLa_{x 关键词： 弛豫性相变 微畴-宏畴 层状钙钛矿 介电性能}     

Bi4-xLaxTi3O12-SrBi4Ti4O15,共生结构铁电材料拉曼光谱研究

在常温下，对La掺杂共生结构铁电陶瓷Bi_4-xLa_xTi_3O_12-SrBi_4-yLayTi_4O_15［BLT-SBLT(x+y),x+y= 0.00, 0.25,0.50,0.75,1.00,1.25,1.50］进行了拉曼光谱研究.结果表明，在掺杂量低于0.50时，La只取代类钙钛矿层中的Bi，当掺杂 量高于0.50后，部分La开始进入(Bi_2O_2)^2+层. La取代(Bi_2O_2)^2+层中的部分Bi以后，(Bi_2O_2)^2+层结构发生变化 ，原有的绝缘层和空间电荷库的作用减弱，导致材料剩余极化下降. La掺杂量增至1.50时，样品出现弛豫铁电性，这与30cm^-1以下模的软化相对应，说明La掺杂可引起材料 的结构相变. 关键词： Bi4-xLaxTi3O12-SrBi4Ti4O15 La掺杂 声子模 拉曼频移     

一个不连续映象中的混沌稳定或混沌抑制

借助于一个张弛振子模型和与之相应的不连续映象说明了在这类系统中瞬态集的映蔽效应会产生三种区域：1）稳定混沌区，在此区域中不存在周期窗口，混沌轨道是结构稳定的；2）完全锁相区，在此区域中混沌被抑制，只存在周期运动；3）准周期区域，在此区域中混沌被抑制，只存在准周期或临界稳定的周期运动．这种思想被用来解释在一个实际张弛振子电路中观察到的稳定混沌区和完全锁相区 关键词：     

La掺杂SrBi4Ti4O15铁电材料性能研究

按x=0 0 0 ,0 10 ,0 2 5 ,0 5 0 ,0 75和 1 0 0 ,采用固相烧结工艺 ,制备了不同La掺杂量的SrBi4-xLaxTi4O1 5的陶瓷样品 .用x射线衍射对其微结构进行了分析 ,并测量了铁电、介电性能 .结果发现 ,La掺杂未改变SrBi4Ti4O1 5的晶体结构 .随掺杂量的增加 ,样品的矫顽场 (Ec)下降 ,剩余极化 ( 2Pr)先增大 ,后减小 .在x =0 2 5时 ,2Pr 达到极大值 ,为2 4 2 μC·cm- 2 ,这时Ec=60 8kV·cm- 1 ,与SrBi4Ti4O1 5相比 ,2Pr 增加了近 5 0 % ,而Ec 下降了近 2 5 % ,材料铁电性能显著提高 .SrBi4-xLaxTi4O1 5的相变温度Tc 随x的增加逐渐降低 ,x =0 2 5时 ,Tc=45 1℃ .在x =0 75 ,1 0 0时 ,样品出现弛豫铁电体的典型特征