结构设计对铁电薄膜系统电滞回线的影响

为制备符合Si集成铁电器件要求的高质量Si基铁电薄膜，采用溶胶—凝胶(sol—gel)工艺，制备了MFM及MFS结构的铁电薄膜系统，研究了不同结构及不同衬底对铁电薄膜系统铁电性能及电滞回线的影响，并对这些差异产生的主要影响因素进行了分析，在此基础上，提出并制备了Ag／Pb(Zr0.52Ti0.48)O3／Bi4Ti3O12／p—Si多层结构，该结构铁电薄膜系统的铁电性能及电滞回线的对称性有明显改善，有望应用于Si集成铁电器件。     

Effect of NiZnFeO4 content on PZT-pZN + NiZnFeO4 magnetoelectric composite

We fabricated and characterized the magnetoelectric (ME) properties of 3-0 ME composite materials comprised of the high piezoelectric voltage coefficient material, 0.9Pb(Zr0.52Ti0.48)O3-0.1 Pb(Zn1/3Nb2/3)O3 + 0.005Mn (PZT-PZN), and the magnetostrictive material, Ni0.8Zn0.2Fe2O4 (NZF). As the ME effect is generated by the product coupling between the piezoelectric properties and the magnetostrictive properties, the NZF content should be optimized for a higher ME coefficient. The dielectric constant and spontaneous polarization (P) were decreased with increasing NZF content before the percolation of the NZF particulates. However, as the NZF content exceeded the percolation content, the dielectric loss was dramatically increased due to the low resistivity of NZF. While the piezoelectric constant was decreased with increasing NZF content, the maximum magnetization was linearly increased. When we combined the piezoelectric and magnetostrictive effects, the ME composite sintered at 1200 degrees C with 20% NZF showed a maximum dE/dH of 27 mV/cm x Oe at a magnetic bias of 1240 Oe.     

Controllable phase connectivity and magnetoelectric coupling behavior in CoFe(2)O(4)-Pb(Zr,Ti)O(3) nanostructured films

Magnetoelectric CoFe(2)O(4)-Pb(Zr,Ti)O(3) nanostructured films with various phase connectivity patterns were prepared by a pulsed laser deposition method. It was found that the microstructure as well as the phase connectivity pattern of the film varied remarkably with the variation of phase content ratio. All composite nanofilms exhibit evident ferromagnetic and ferroelectric characteristics, as well as distinct magnetoelectric coupling behavior upon increasing the magnetic field. The correlation between the phase connectivity pattern and magnetoelectric coupling behavior for the composite nanofilm was revealed. This work provides an efficient avenue to modulate the magnetoelectric coupling behavior for the ferroelectric-ferromagnetic composite nanofilm.     

Role of precursors in the formation of lead zirconate titanate thin films

Thin ferroelectric Pb(Zr_0.48Ti_0.52)O₃ lead zirconate titanate films have been prepared on platinized silicon substrates via chemical solution deposition. The starting film-forming solutions were prepared by reacting lead acetate with Ti and Zr alkoxides in 2-methoxyethanol. The electrical properties of the films were shown to depend on the Ti and Zr alkoxide precursors used in synthesis. The nature of the zirconium alkoxide had the strongest effect on the properties of the films. The best properties were obtained with zirconium n-propoxide.     

添加助烧剂对CoFe_2O_4/BaTiO_3复相多铁材料性能的影响

采用固相合成法制备出尖晶石结构CoFe_2O_4粉末和钙钛矿结构BaTiO_3,并按照2∶8的摩尔比将粉末混合,随后添加不同的助烧剂。研究多种助烧剂对制备出的CoFe_2O_4/BaTiO_3复相多铁材料成分、微观形貌、介电性能、铁电性和磁性能的影响。结果表明:仅添加助烧剂Bi2O3,难以达到烧结致密的目的;当助烧剂中含有CaCO3-SiO2时,有效提高了CoFe_2O_4/BaTiO_3复相多铁材料的烧结性能,在相同的烧结温度下,CoFe_2O_4/BaTiO_3复相多铁材料致密度得到提升,且介电性能、铁电性、磁性能均有一定程度的优化。     

Sol-Gel Based Soft Lithography and Piezoresponse Force Microscopy of Patterned Pb(Zr_(0.52)Ti _(0.48))O_3 Microstructures

Sol-gel based soft lithography technique has been developed to pattern a variety of ferroelectric Pb(Zr0.52Ti0.48)O3(PZT) microstructures,with feature size approaching 180 nm and good pattern transfer between the master mold and patterned films.X-ray diffraction and high-resolution transmission electron microscopy confirm the perovskite structure of the patterned PZT.Piezoresponse force microscopy(PFM) and switching spectroscopy piezoresponse force microscopy(SSPFM) confirm their piezoelectricity and ferroe...     

紫外脉冲激光淀积法制备Pb(Ta0.05Zr0.48Ti0.47)O3薄膜的铁电性质

用紫外脉冲激光淀积方法在Pt／TiO2／SiO2／Si(001)衬底上制备了La1-xSrxCoO3／Pb(Ta0.05Zr0.48Ti0.47)O3(PTZT)／La1-xSrxCoO3异质结构薄膜。发现底电极La0.25Sr0.75CoO3可以诱导PTZT薄膜沿(001)方向取向生长。在500kHz和5V的工作电压下铁电电容器La0.25Sr0.75CoO3/PTZT／La0.25Sr0.75CoO3经过5×1010次反转之后,仍保持其初始电极化的96％。此异质结构横截面的扫描电镜照片表明界面上没有明显的因化学反应导致的第二相存在。     

力电多场鼓包法测定PZT铁电薄膜的横向压电系数

为表征Pb(Zr_(0.52)Ti_(0.48))O_3(PZT)薄膜的横向压电性能,以纯力场鼓包测试模型和铁电薄膜材料压电方程为基础,推导了PZT铁电薄膜的力电耦合鼓包本构模型。采用溶胶-凝胶法制备了PZT铁电薄膜,并通过化学腐蚀法获得PZT薄膜鼓包样品。在外加电压为0~14V的条件下进行鼓包测试。结果表明,在纯力场作用下,PZT薄膜的弹性模量和残余应力分别为91.9GPa和36.2MPa;随着电压从2V变化到14V,PZT薄膜的横向压电系数d31从-28.9pm/V变化到-45.8pm/V。本工作所发展的力电耦合鼓包测试技术及力电耦合鼓包本构模型为评价铁电薄膜材料的横向压电性能提供了一种有效的分析方法。     

Hydrothermal temperature effect on magnetoelectric coupling of Ni/Pb(Zr0.52Ti0.48)O3 bilayers

Magnetoelectric (ME) Ni/Pb(Zr_0.52Ti_0.48)O₃ bilayers have been prepared by hydrothermal method. The structure and ferroelectric properties of the Pb(Zr_0.52Ti_0.48)O₃ (PZT) thin films prepared at various hydrothermal temperatures are characterized by X-ray diffraction and ferroelectric testing. With the hydrothermal temperature increasing the grain size of the PZT thin films gradually decreases leading to a gradual increase of the coercive field and a decrease of the remnant polarization of the Ni/PZT bilayers. The ME voltage coefficient of the Ni/PZT bilayers gradually decreases as hydrothermal temperature increases. The large ME coefficient makes these Ni/PZT bilayers possible for applications in multifunctional devices such as electromagnetic sensor, transducers and microwave devices.     

Self-separated PZT thick films with bulk-like piezoelectric and electromechanical properties

Self-separated Pb(Zr(0.52)Ti(0.48))O(3) (PZT) films were processed by a hydrothermal deposition and a rapid thermal separation method, followed by a sol-gel filling and sintering process. The films possess excellent piezoelectric and electromechanical properties close to those of bulk material. The maximum remnant polarization is over 30 μC/cm(2) and the electromechanical coupling factor (k(t)) reaches as high as 0.52. The unique microstructure characteristics of the PZT films, such as their highly dense structure, columnar grains, well-connected grain boundaries, and well-dispersed nanopores, could all contribute to the enhanced piezoelectric and electromechanical properties.     

Structural properties of Pb(Zr0.53Ti0.47)O3/YBa2Cu3O7-δ heterostructures on SrTiO3 substrates

The structures of ferroelectric Pb(Zr0.53Ti0.47)O3 and high-Tc YBa2Cu3O7– superconductor integrated films on (0 0 1) SrTiO3 substrate prepared by the r.f./d.c. magnetron sputtering method have been studied by X-ray grazing incidence reflectivity, diffuse scattering and high-resolution X-ray diffraction methods combined with atomic force microscopy (AFM) and SEM techniques. The results of high-resolution X-ray diffraction show that the quality of Pb(Zr0.53Ti0.47)O3 improved as the thickness increased. On the other hand, the crystalline quality of YBa2Cu3O7– deteriorated and the superconducting transition temperature, Tc, decreased as the thickness of Pb(Zr0.53Ti0.47)O3 increased. The strain state was similar for different thickness samples and the lattice mismatch strain in the Pb(Zr0.53Ti0.47)O3 layer was almost totally relaxed. The root mean square (r.m.s.) roughness at Pb(Zr0.53Ti0.47) O3/YBa2Cu3O7– interface was determined to be about 1.7±0.3 nm by X-ray specular reflectivity. The r.m.s. roughness at the surface of Pb(Zr0.53Ti0.47)O3/YBa2Cu3O7– bilayer samples was about 1.5 to 2.0±0.3 nm which was larger than that of YBa2Cu3O7– single-layer sample measured by both X-ray specular reflectivity and AFM methods. The results from AFM and SEM show that the morphological characteristics of the Pb(Zr0.53Ti0.47)O3 layer surface were large grains covering about 10% in area distributed on a fine-grained matrix. © 1998 Chapman & Hall     

Magnetoelectric properties of CoFe2O4–Pb(Zr0.52Ti0.48)O3 multilayered composite film via sol–gel method

CoFe₂O₄–Pb(Zr_0.52Ti_0.48)O₃ (CFO–PZT) multilayered composite film was prepared on Pt/Ti/SiO₂/Si substrate via a sol–gel method and spin-coating technique. Results show that PZT and CFO phases exist in the composite film, calcined at 700 °C, besides substrate phase, and no obvious impurity phases can be detected. The composite film exhibits layered structure with obvious boundary between CFO and PZT films. Ferroelectric and ferromagnetic properties were simultaneously observed in the composite film, evidencing the ferroelectric and ferromagnetic properties in the composite film. The composite film exhibits both good magnetic and electric properties, as well as, magnetoelectric (ME) effect. The saturation magnetization value of the composite film is lower than that of the pure CFO film derived by the same processing as a result of the effect of the nonferromagnetic PZT layers. Ferroelectric hysteresis loops reveal that saturated polarization and remanent polarization of the composite film are lower than those of the pure PZT films. The composite film exhibits a very large ME effect, which makes the composite film attractive for technological applications as devices.     

Magnetoelectric coupling in ordered arrays of multilayered heteroepitaxial BaTiO₃/CoFe₂O₄ nanodots

Fully epitaxial BaTiO(3)/CoFe(2)O(4) ferroelectric/ferromagnetic multilayered nanodot arrays, a new type of magnetoelectric (ME) nanocomposite with both horizontal and vertical orderings, were fabricated via a stencil-derived direct epitaxy technique. By reducing the clamping effect, ferroelectric domain modification and distinct magnetization change proportional to different interfacial area around the BaTiO(3) phase transition temperatures were found, which may pave the way to quantitative introducing of ME coupling at nanoscale and build high density multistate memory devices.     

水热法合成单分散锆钛酸铅压电陶瓷粉体

以硝酸铅、氧氯化锆、钛酸四丁酯、氢氧化钾和氨水为原料,以乙醇和水的混合液为溶剂,采用水热法合成Pb(Zr0.52Ti0.48)O3(PZT)压电陶瓷粉体。通过X射线衍射和扫描电镜对合成粉体进行表征,并研究Pb元素物质的量与Zr及Ti两种元素物质的量之和的比n(Pb)/n(Zr+Ti)和矿化剂KOH浓度对粉体物相和形貌的影响。结果表明:n(Pb)/n(Zr+Ti)=1.4时,可以合成单一晶相的PZT,颗粒的立方体形貌规则清晰且无团聚,结晶良好;在200℃、反应溶剂乙醇和水的体积比为2∶1、n(Pb)/n(Zr+Ti)=1.4的条件下,当KOH浓度由1 mol/L增加到4 mol/L时,立方体形貌的PZT粉体的粒径由1.5μm减小到0.2μm。     

Self-amplified magnetoelectric properties in a dumbbell-shaped magnetostrictive/piezoelectric composite

We report magnetoelectric (ME) properties in a dumbbell-shaped metallic glass alloy/Pb(Zr(x)Ti(1-x))O(3) laminated composite, yielding a magnetic field amplification resulting from magnetic flux concentration effects of the dumbbell-shaped design. Compared with the traditional rectangular structures, the modified geometry results in an effective improvement in the ME coefficient, a significant decrease in the required dc magnetic bias field, and an enhancement in magnetic field sensitivity.     

Design and fabrication of bimorph transducer for optimal vibration energy harvesting

High energy density piezoelectric composition corresponding to 0.9Pb(Zr0.56Ti0.44)O3–0.1Pb[(Zn0.8/3Ni0.2/3) Nb2/3]O3 + 2 mol% MnO2 (PZTZNN) and 0.8[Pb(Zr0.52Ti0.48) O3]-0.2[Pb(Zn1/3Nb2/3)O3] (PZTPZN) were synthesized by conventional ceramic processing technique using three different sintering profiles. Plates of the sintered samples were used to fabricate the piezoelectric bimorphs with optimized dimensions to exhibit resonance in the loaded condition in the range of ~200 Hz. An analytical model for energy harvesting from bimorph transducer was developed which was confirmed by experimental measurements. The results of this study clearly show that power density of bimorph transducer can be enhanced by increasing the magnitude of product (d ? g), where d is the piezoelectric strain constant and g is the piezoelectric voltage constant.     

Ag/Bi4Ti3O12/p-Si异质结的制备及其C-V特性研究

为制备符合铁电存储器件要求的高质量铁电薄膜,采用溶胶-凝胶(Sol-Gel)工艺,制备了Si基Bi4Ti3O12铁电薄膜及MFS结构的Ag/Bi4Ti3O12/P-Si异质结,对Bi4Ti3O12薄膜的相结构特征及异质结的C-V特性进行了测试与分析.XRD图谱显示,Si基Bi4Ti3O12薄膜具有沿c-轴择优取向生长的趋势,而Ag/Bi4Ti3O12/p-Si异质结顺时针回滞的C-V特性曲线则表明,该异质结可实现电极化存储.此外,对该异质结C-V特性曲线的非对称及向负偏压方向偏移的产生原因也进行了分析.在此基础上,为提高铁电薄膜的铁电性能及改善其C-V特性提出了合理的结构设想.     

Processing and magneto-electric properties of sol–gel-derived Pb(Zr0.52Ti0.48)O3–Ni0.8Zn0.2Fe2O4 2-2 type multilayered films

Pb(Zr_0.52Ti_0.48)O₃–Ni_0.8Zn_0.2Fe₂O₄ (PZT–NZFO) multilayered thin films with various volume fractions of the PZT phase (100, 74, 58, 48, 33, and 0%) were prepared on Pt/Ti/SiO₂/Si substrates using sol–gel spin-coating method. X-ray diffraction shows polycrystalline structure and scanning electron microscopy reveals good multilayer morphology of the composite thin film as annealed at 700 °C in air. The thickness of the composite films was estimated in the range of ~400 to ~600 nm. The ferroelectric and magnetic properties were measured as function of the volume fractions of the PZT phase. The magnetoelectric (ME) effect was investigated under various bias magnetic fields. The maximum ME voltage coefficient (α _E  = dE/dH) is 278 mV/cmOe for the composite film with the volume fractions of the PZT phase of ~48%.     

Structural defects and local chemistry across ferroelectric–electrode interfaces in epitaxial heterostructures

We present a detailed investigation of the chemistry at the growth interface between the bottom electrode and ferroelectric film in (001)-oriented epitaxial ferroelectric thin-film heterostructures. Three different ferroelectric systems, namely PbZr_0.2Ti_0.8O₃, PbZr_0.52Ti_0.48O₃, and BaTiO₃ deposited on SrRuO₃/SrTiO₃, were investigated to compare and contrast the role of lattice mismatch versus the volatility of the deposited cation species. A combination of transmission electron microscopy-based imaging and spectroscopy reveals distinct correlations among the ferroelectric thin-film composition, the deposition process, and chemical gradients observed across the ferroelectric–electrode interface. Sr diffusion from the electrode into the ferroelectric film was found to be dominant in PbZr_0.2Ti_0.8O₃/SrRuO₃/SrTiO₃ thin films. Conversely, Pb diffusion was found to be prevalent in PbZr_0.52Ti_0.48O₃/SrRuO₃/SrTiO₃ thin films. The BaTiO₃/SrRuO₃/SrTiO₃ heterostructure was found to have atomically sharp interfaces with no signature of any interdiffusion. We show that controlling the volatility of the cation species is as crucial as lattice mismatch in the fabrication of defect-free ferroelectric thin-film devices.     

Preparation and ferroelectric properties of Bi-modified lead zirconate titanate thin film

We have studied the structural and electrical properties of bismuth-modified lead zirconate titanate thin films. Specimens with various Bi contents, (Pb1−3/2xBix) (Zr0.52 Ti0.48) O3 (PBZT) thin films, were prepared on a Pt-coated Si wafer by the sol–gel method. Ferroelectricity confirmed by the measurement of dielectric constant and P–E hysteresis loop was found for specimens below x = 0.25, in which the values of both dielectric constant and remanent polarization were decreased with increasing Bi contents. The behaviors of the electrical properties with Bi content corresponded to the structural changes by increasing non-ferroelectric cubic phase with increasing Bi contents, which was thought to be due to the vacancies in Pb-sites created by the substitution of Bi into Pb.