LaxBi2-xTi4O11的合成及相变研究

合成了Ｌａ_xＢｉ_2-xＴｉ₄Ｏ₁₁系列样品，并完成了它们的喇曼光谱和ｘ射线衍射测量；结果表明，该体系在Ｘ＝１．２经历了一次相变，且相变与最低频声子模随Ｘ的变化有关。Ｌａ_0.2Ｂｉ_1.8·Ｔｉ₄Ｏ₁₁的相变温度为２００℃。初步获得Ｌａ₂Ｔｉ₄Ｏ₁₁的结构为正交结构。 关键词：     

Low temperature fired Ni-Cu-Zn ferrite with Bi4Ti3O12

The Ni-Cu-Zn ferrites with different contents of Bi₄Ti₃O₁₂ ceramics (1-8 wt%) as sintering additives were prepared by the usual ceramic technology and sintered at 900 °C to adapt to the low temperature co-fired ceramic (LTCC) technology. The magnetic and dielectric properties of the ferrite can be effectively improved with the effect of an appropriate amount of Bi₄Ti₃O₁₂. For all samples, the ferrite sintered with 2 wt% Bi₄Ti₃O₁₂ has relatively high density (98.8%) and permeability, while the ferrite with 8 wt% Bi₄Ti₃O₁₂ has relatively good dielectric properties in a wide frequency range. The influences of Bi₄Ti₃O₁₂ addition on microstructure, magnetic and dielectric properties of the ferrite have been discussed.     

SrBi2Ta2O9/Bi4Ti3O12复合铁电薄膜的制备与特性研究

采用溶胶凝胶工艺在p-Si衬底上制备了SrBi₂Ta₂O₉/Bi₄Ti₃O₁₂复合铁电薄膜. 研究了SrBi₂Ta₂O₉/Bi₄Ti₃O₁₂复合薄膜的微观结构与生长行为、铁电性能和疲劳特性. 研究表明: Si衬底Bi₄Ti< 关键词： 2Ta₂O₉')" href="#">SrBi₂Ta₂O₉ 4Ti₃O₁₂')" href="#">Bi₄Ti₃O₁₂ 复合铁电薄膜 溶胶凝胶工艺     

Ferroelectric properties of Pr6O11-doped Bi4Ti3O12

Praseodymium doped Bi₄Ti₃O₁₂ (BIT) ceramics with composition Bi_2.9Pr_0.9Ti₃O₁₂ (BPT) were prepared by solid state reaction. These samples have polycrystalline Bi-layered perovskite structure without preferred orientation, and consist of well-developed plate-like grains with random orientation. Pr doping into BIT causes a large shift of the Curie temperature (T_C) of the BIT from 675 to 398 °C. At an electric field of 87 kV/cm, the remanent polarization and the coercive field of the BPT ceramics are 30 μC/cm² and 52 kV/cm, respectively. Furthermore, the dielectric permittivity and the dissipation factor of the BPT ceramics are 300 and 0.003 at 1 MHz, 1 V, and room temperature. Ferroelectric properties of the BPT ceramics are superior to V-doped Bi₄Ti₃O₁₂ (∼20 μC/cm² and 80 kV/cm) and (Sr, Ta)-doped Bi₄Ti₃O₁₂ (∼12 μC/cm² and 71 kV/cm) ceramics. In addition, the dense ceramics of praseodymium-doped B₄Ti₃O₁₂ were obtained by sintering at 1100 °C, about 100-200 °C lower than those of the SrBi₂Ta₂O₉ system.     

Ag/Bi4Ti3O12栅n沟道铁电场效应晶体管制备及存储特性

在溶胶-凝胶工艺获得高质量Bi₄Ti₃O₁₂薄膜的基础上 ，制备了Ag/Bi₄Ti₃O₁₂栅n沟道铁电场效应晶体管. 研 究了Si基Bi₄Ti₃O₁₂薄膜的生长特性及其对铁电薄膜/ 硅的界面状态和铁电场效应晶体管存储特性的影响. 研究表明，在合理的工艺条件下可以获 得具有较高c-轴择优取向的纯钙钛矿相Si基Bi₄Ti₃O₁₂ 铁电薄膜并有利于改善Bi₄Ti₃O₁₂/Si之间的界面特性; 顺时针回滞的C-V特性曲线和C-T曲线表明Ag/Bi₄Ti₃O_{12栅n沟道铁电场效应晶体管具有极化存储效应和一定的极化电荷保持能力; 器件的转移(I< sub>sd}-V_G)特性曲线显示Ag/Bi₄Ti₃O_{12栅n沟道铁电场效应晶体管具有明显的栅极化调制效应. 关键词： 铁电场效应晶体管 4}Ti₃O₁₂')" href="#">Bi₄Ti₃O₁₂ 存储 特性 溶胶-凝胶工艺     

Si基Bi4Ti3O12铁电薄膜的制备与特性研究

采用sol-gel工艺, 在分层快速退火的工艺条件下成功地制备了高质量Si基Bi_{4Ti3O12铁电薄膜. 研究了Si基Bi4Ti3O12薄膜的生长行为、铁电性能、C-V特性和疲劳特性. 研究表明: Si基Bi4Ti3O12薄膜具有随退火温度升高沿c轴择优生长的趋势; 退火温度通过影响薄膜的晶粒尺寸、生长取向和薄膜中载流子的浓度来改变Si基Bi关键词： sol-gel法 铁电薄膜 4Ti3O12')" href="#">Bi4Ti3O12 C-V特性}     

Ferroelectric and dielectric properties of La/Mn co-doped Bi4Ti3O12 ceramics

La/Mn co-doped Bi4Ti3O12 ceramics,Bi3.25La0.75Ti3-xMnxO12(x=0.02,0.04,0.06,0.08),were prepared by the solid-state reaction method.The influence of manganese substitution for the titanium part in Bi 3.25 La 0.75 Ti 3 O 12 on the sintering behaviour,microstructure,Raman spectra and electrical properties was investigated.The experimental results show that the phase composition of all samples with and without manganese doping,sintered at 1000 ℃,consists of a single phase with a bismuth-layered structure belonging to the crystalline phase Bi4Ti3O12.There is no evidence of any impurity phase,but a small change in crystallographic orientation is observed.The Curie temperature of Bi3.25La0.75Ti3-xMnxO12 ceramics is steadily shifted to lower temperature with increasing Mn-doping content.Moreover,the remnant polarisation(Pr) of Bi3.25La0.75Ti2.92Mn0.08O12 samples increases with Mn-doping content,and the Bi3.25La0.75Ti2.92Mn0.08O12 sample exhibits the largest P r of 16.6 μC/cm 2.     

La掺杂对Bi4Ti3O12薄膜铁电性能的影响

利用Sol-Gel法在Pt/Ti/SiO₂/Si衬底上制备出Bi₄Ti₃O₁₂和Bi_3.25La_0.75Ti₃O₁₂薄膜，研究了La掺杂对Bi₄Ti₃O₁₂薄膜的晶体结构、铁电性能和疲劳特性的影响，发现La掺杂没有改变Bi₄Ti₃O₁₂薄膜的基本晶体结构，并且提高了Bi₄Ti₃O₁₂铁电薄膜的剩余极化值和抗疲劳性能，对La掺杂改善Bi₄Ti₃O₁₂铁电薄膜性能的机理进行了讨论. 关键词： 铁电性能 4Ti₃O₁₂薄膜')" href="#">Bi₄Ti₃O₁₂薄膜 3.25La_0.75Ti₃O₁₂薄膜')" href="#">Bi_3.25La_0.75Ti₃O₁₂薄膜 sol-gel法 La掺杂     

Temperature dependent Raman scattering in polycrystalline Bi4Ti3O12 thin films

Polycrystalline Bi₄Ti₃O₁₂ thin films were prepared on quartz substrates by pulsed laser deposition. The films were crystallized in the orthorhombic layer perovskite structure confirmed by X-ray diffraction and Raman spectroscopy. The Raman spectra are strongly dependent on temperature. A subtle phase transition in the temperature range 473-573 K exists in polycrystalline BTO thin films, which is evidenced by the disappearance of the Raman band at 116 cm⁻¹ and appearance of a new Raman band at 151 cm⁻¹. The two broad Raman bands centered at the 57 and 93 cm⁻¹ at 300 K break up into clusters of several sharp Raman peaks at 77 K, due to monoclinic distortion of orthorhombic structure at low temperature in the as-prepared Bi₄Ti₃O₁₂ thin films.     

Combinatorial exploration of flux material for Bi4Ti3O12 single crystal film growth

The combinatorial approach to materials synthesis was employed for the quick screening of a flux material for liquid phase-mediated epitaxy of Bi₄Ti₃O₁₂ single crystal film. A series of ternary flux libraries composed of two self-fluxes (Bi₂O₃ and Bi₄Ti₃O₁₂) and an impurity flux (VO_x, WO_x, CuO_x, BiPO_x, BaO, MoO_x) were fabricated on the SrTiO₃ (0 0 1) substrates. Then, stoichiometric Bi₄Ti₃O₁₂ was grown on each one of these flux libraries at a temperature presumed to melt the flux. High-throughput characterization with the concurrent X-ray diffraction (XRD) method resulted in the discovery of a novel flux material, CuO, containing Bi₂O₃, for Bi₄Ti₃O₁₂ single crystal film.     

Si基Bi3.25La0.75Ti3O12铁电薄膜的制备与特性研究

采用Sol-Gel工艺低温制备了Si基Bi_3.25La_0.75Ti₃O₁₂铁电薄膜.研究了退火温度对薄膜微观结构、介电特性与铁电性能的影响.500℃退火处理的Bi_3.25La_0.75Ti₃O₁₂薄膜未能充分晶化，晶粒细小且有非晶团聚，介电与铁电性能均较差.高于550℃退火处理的Bi_3.25La_{0.75 关键词： 铁电薄膜 3.25}La_0.75Ti₃O₁₂')" href="#">Bi_3.25La_0.75Ti₃O₁₂ Sol-Gel工艺     

Bi2Ti2O7/Si薄膜的制备及C-V特性研究

采用化学溶液分解法(CSD)在Si衬底上制备了Bi₂Ti₂O₇薄膜.X射线双晶衍射和原子力显微镜检测表明,所制备的薄膜主要为Bi₂Ti₂O₇相的多晶材料.同时还研究了AuBi₂Ti₂O₇/n-Si(100)结构的电容电压(C-V)特性,结果表明,在Bi₂Ti₂O关键词： C-V特性 2Ti₂O₇薄膜')" href="#">Bi₂Ti₂O₇薄膜 电荷迁移     

Influence of mobile space charges on electrical properties of ferroelectric Bi3.5La0.5Ti3O12 thin films

Lanthanum-substituted bismuth titanate, Bi_3.5La_0.5Ti₃O₁₂ (i.e., x=0.5 in Bi_4−xLa_xTi₃O₁₂), thin films have been grown on Pt/Ti/SiO₂/Si substrates using pulsed laser deposition. The frequency dependence of the real part ε′(ω) and the imaginary part ε″(ω) of the dielectric constant has been studied. The ε′(ω) does not show any sudden change within the frequency range of 10²-10⁶ Hz. In contrast, the ε″(ω) shows a large dispersion as frequency decreases. The observed relaxation behavior in ε″(ω) can be explained in terms of a migration of oxygen vacancies in (Bi₂O₂)²⁺ layers, not in Bi₂Ti₃O₁₀ perovskite layers.     

Lanthanum-doped Bi4Ti3O12 ceramics prepared by high-pressure technique

We present an effective way in this paper to increase the density of lanthanum doped bismuth titanate ceramics, Bi4-xLaxTi3O12 (BLT), thereby significantly improving the performance of the BLT ceramics. Dense BLT ceramicses, Bi4-xLaxTi3O12 (x = 0.25, 0.5, 0.75, 1.0), are prepared by using nanocrystalline powders fabricated by a-gel method and high-pressure technique. The microstructures of the BLT ceramicses prepared separately by conventional-pressure and high-pressure techniques are investigated by using x-ray diffraction and transmission electron microscope. The influence of La-doping on the densification of bismuth titanate ceramics is investigated. The experimental results indicate that the phase compositions of all samples with various lanthanum dopings sintered at 900°C possess layer-structure of Bi4Ti3O12 . The green compacts are pressed under 2.5 GPa, 3.0 GPa, 3.5 GPa and 4.0 GPa, separately. It is found that the density of BLT ceramics is significantly increased due to the decreasing of porosity in the green compacts by high-pressure process.     

Photocatalytic degradation efficacy of Bi4Ti3O12 micro-scale platelets over methylene blue under visible light

〈001〉 textured Bi₄Ti₃O₁₂ platelets with micro scale size were synthesized by a facile molten salt method. The photocatalytic activities of the as-prepared samples were measured with the photodegradation of methylene blue at room temperature under visible light irradiation. The Bi₄Ti₃O₁₂ with the aspect ratio of 35 exhibited good absorption in the visible light region and the photodegradation against methylene blue was higher than that of anatase TiO₂ reference, showing that the high degree of preferred {001} facets on the plate surface benefits the electronic transmission. In addition, the layer-pervoskite structure facilitates the mobility of the photogenerated carriers and hampers their recombination. The above results indicated that the large specific surface area of the as-prepared samples could attribute to the presence of a number of oxygen vacancies and then lead to the good photo-electric property. This work proposed an alternative way to tailor the structure of micro-sized platelets to get excellent properties comparable to the nano materials.     

La substitution in four-layers Aurivillius phase SrBi4Ti4O15

Ceramics with the nominal composition of SrBi_4−xLa_xTi₄O₁₅ have been prepared within the range of 0≤x≤1.8, and the dielectric properties are investigated. Single phase SrBi_4−xLa_xTi₄O₁₅ solid solution exists until the secondary phase of La_2/3TiO₃ appears at x=1.6. The Curie temperature is 520 °C for pure SrBi₄Ti₄O₁₅, and it shifts to low temperature with increasing x, which is due to the smaller structural distortion caused by La³⁺ substitution. In addition, the dielectric constant anomaly is suppressed with the substitution. No dielectric relaxation behavior is observed. When x≥1.2, the paraelectric state is attained in the present ceramics. La³⁺ substitution effects on the SrBi₄Ti₄O₁₅ ceramics are also compared with the previous work on Bi_4−xLa_xTi₃O₁₂.     

Large memory window in the vanadium doped Bi4Ti3O12 thin films

We report the enhancement of ferroelectric properties in vanadium-doped Bi₄Ti₃O₁₂ (BIT) thin films prepared by rf magnetron sputtering method for MFM and MFIS structures. The optimal sputtering parameters of the as-deposited Bi_3.9Ti_2.9V_0.08O₁₂ (BTV) ferroelectric films for different depositing times were obtained. Compared to the undoped BIT, vanadium doped BIT (BTV) showed better physical and electrical characteristics. The as-deposited BTV showed a remanent polarization (2P _r ) of 23 μC/cm², higher than the value of 16 μC/cm² for BIT, as the measured frequency was 100 kHz. For BTV thin films in the MFIS structure, the leakage current density and the memory window decreased, the change ratio of capacitance critically increased as the depositing time increased from 30 to 120 min. Regarding the measured physical properties, the micro-structure and thickness of as-deposited undoped and vanadium doped BIT thin films were obtained and compared by XRD patterns and SEM images.     

Dielectric properties of Bismuth Titanate (Bi4Ti3O12) synthesized using solution combustion route

Ferroelectric Bismuth Titanate (Bi₄Ti₃O₁₂) was prepared by solution combustion route with glycine as fuel. The single phase Bismuth Titanate was obtained after calcination at 800 °C, which was confirmed with the help of X-ray diffraction studies and EDS analysis. SEM micrographs of the calcined powders show agglomerated particles, which is typical of combustion synthesis. Behavior of dielectric constant and dielectric loss as a function of temperature of as prepared sample are reported here. Ferroelectric to paraelectric phase transition occurs at the temperature T_c∼650 °C. Impedance studies were made in the frequency range from 1 KHz to 1 MHz. The semicircles observed in the complex impedance diagrams indicate deviation from the Debye behavior. Activation energy of the sample around T_c is found to be ∼0.35 eV and below T_c is ∼0.13 eV, which was calculated using the Arrhenius plots.     

Raman spectroscopic study of ceramic Sr2Bi4Ti5O18

Raman spectra of ceramic Sr2Bi4Ti5O18 （SBTi5） are reported to consist of four different Raman bands. Temperature-dependent spectra reveal the relationship between the lattice vibration and the material＇s structure. There appears a relatively large change in structure of the material at about 273K, The anharmonic potential of the material has a great influence on its phonon mode full width at half maximum （FWHM）, which can be expressed by a function of temperature. Theoretical fittings of the FWHMs for the two modes at around 312 cm^-1 and 464cm^-1 indicate that the latter phonon mode is more anharmonic than the former one.     

Polymorphism in Bi2Sn2O7

Single crystals of Bi₂Sn₂O₇ were grown in a Bi₂O₃ flux. Phase transitions were identified at about 90 and 680° using X-ray, SHG, DSC, dielectric, and optical data. γ-Bi₂Sn₂O₇, which exists above 680°C is centric and cubic with a = 10.73 Å at 700°, and it probably has the ideal pyrochlore structure. β-Bi₂Sn₂O₇, which exists between 680° and about 90°C, is acentric but remains cubic with a = 21.40 Å. α-Bi₂Sn₂O₇, which exists from about 90°C to below room temperature, is acentric and noncubic, probably tetragonal with a = 21.328 and c = 21.545 Å. The α-β transition is first order, and the β-γ transition appears to be second order. Substitutions of Pb²⁺ or Cd²⁺ for Bi³⁺ and of Ga³⁺, Rh³⁺ Sc³⁺, In³⁺, Sb⁵⁺ Nb⁵⁺ or Ta⁵⁺ for Sn⁴⁺ lower the α-β transition temperature.