激光脉冲外延生长Pb(Zr0.52Ti0.48)O3薄膜及其特性研究

利用激光脉冲法在LaAlO3衬底上沉积制备LaNiO3薄膜作为底电极并外延生长(100) Pb(Zr0.52Ti0.48)O3铁电薄膜,系统研究了生长温度对PZT外延结构和电学特性的影响.研究发现当生长温度高于550℃时即可得到外延(100)PZT薄膜.在对所制备的PZT薄膜的结构和性能测试表明,650℃下生长的PZT薄膜外延性最佳,并且表现出优异的介电和铁电性能,介电常数ε、剩余极化Pr和矫顽场Ec分别为900、26.5 μC/cm2和52.1kV/cm.试验还证实这种外延PZT薄膜具有优良的抗疲劳特性,可用于铁电存储器的制备中去.     

Pb1-3x/2Eux(Zr0.52,Ti0.48)O3纳米粉的溶胶-凝胶合成

采用改进的溶胶－凝胶法制备出稀土铕掺杂ＰＺＴ（ＰＥＺＴ）的纳米粉,粒径约为２０ｎｍ．由ＸＲＤ分析了Ｅｕ的掺入对ＰＺＴ微观结构的影响,确定了Ｅｕ的最佳掺入量≤7％,分析了Ｅｕ在ＰＺＴ中的占位情况．     

部分草酸铅法共沉淀合成Pb(Zr0.52Ti0.48)O3(PZT)粉体

结合部分草酸铅固相反应法的优点对共沉淀法进行改进,发展了一种合成锆钛酸铅(PZT)粉体新工艺.在该工艺中,首先利用共沉淀法制备Zr、Ti的羟基氧化物共沉淀((Zr0.52Ti0.48)O(OH)2,ZTOH),然后以草酸为沉淀剂,在含有ZTOH沉淀物的悬浮液中沉淀铅离子,得到合成PZT粉体的前驱体粉体.利用DTA、TG和XRD对前驱体的热分解行为和相转化过程进行了研究,利用场发射扫描电镜(FESEM)对前驱体的形貌演化进行了观察.前驱体粉体经过700℃煅烧2h,转化为晶化良好的纯相钙钛矿PZT粉体.     

Microstructure and electrical properties of Pb(Zr0.52Ti0.48)O3 ferroelectric films on different bottom electrodes

The crystalline quality, dielectric and ferroelectricity of the Pb(Zr_0.52Ti_0.48)O₃ (PZT) films deposited on the LaNiO₃ (LNO), LNO/Pt and Pt bottom electrodes were comparatively analyzed to investigate the possibility for their application. LNO thin films were successfully prepared on Si (100) and Pt(111)/Ti/SiO₂/Si substrates by modified metallorganic decomposition (MOD). The PZT thin films were spin-coated onto the LNO, LNO/Pt and Pt bottom electrodes by sol–gel method. The crystallographic orientation and the microstructure of the resulting LNO films and PZT thin films on the different bottom electrodes were characterized by X-ray diffraction analysis. The dielectric and ferroelectric properties of PZT films on the different bottom electrodes are discussed. The PZT films deposited onto Pt/Ti/SiO₂/Si and LNO/Si substrates show strong (110) and (100) preferred orientation, respectively, while the films deposited onto LNO/Pt/Ti/SiO₂/Si substrates show the peaks of mixed orientations. PZT films on LNO and LNO/Pt bottom electrodes have larger dielectric constant and remnant polarizations compared with those grown on the Pt electrode.     

Effects of excess Pb on structural and electrical properties of Pb(Zr0.48Ti0.52)O3 thin films using MOD process

Pb(Zr_0.48Ti_0.52)O₃ thin films at 20% excess Pb were synthesized on Pt/Ti/SiO₂/Si(100) substrates at different annealing temperatures by a metal-organic decomposition process. The microstructure of the PZT films was investigated by x-ray diffraction and atomic force microscopy. The composition of the films was characterized by Rutherford Backscattering Spectroscopy (RBS). These results showed that The PZT films have perovskite phase coexisted with PbO₂ phase. The PbO₂ phase mainly was formed by excess Pb which congregate at boundaries of crystalline grains during the annealing process and may be absorbed part of oxygen ion at normal sites, thus leading to an increase of oxygen vacancies in the PZT film. PbO₂ phase and oxygen vacancies act as pinning centres, which has an effect on the ferroelectric domain switching. This eventually resulted in an increase of fatigue rate in PZT films.     

退火工艺对溶胶凝胶Pb(Zr0.52Ti0.48)O3薄膜残余应力的影响

使用溶胶凝胶法制备了Pb(Zr0.52Ti0.48)O3 铁电薄膜,分别利用原子力显微镜、X射线衍射及面探扫描技术分析了薄膜的组织结构,并运用掠入射X射线衍射法研究了不同工艺条件下制备的薄膜的残余应力.研究表明溶胶凝胶薄膜在600℃退火30min后完全晶化,组织结构均匀.不同工艺下制备的薄膜均受残余拉应力,随着退火温度及退火时间的延长,薄膜中的残余应力逐渐增大,而随着薄膜厚度的增加,残余应力先增大然后减小.     

Influence of Li doping on domain wall motion in Pb(Zr0.52Ti0.48)O3 films

Li-doped PbZr_0.52Ti_0.48O₃ (PZT) films were utilized to study the effect of A-site acceptor dopants on the mobility of ferroelectric domain walls. For chemical solution-deposited PZT films 2 μm in thickness doped with 1–3 mol% Li, the low-field dielectric permittivity remained between 1200 and 1300. With increasing Li concentration, the reversible Rayleigh constants ε _init increased from 1080 for undoped PZT films to 1240 for the films doped with 3 mol% Li, while the irreversible Rayleigh parameter showed a peak value at 1 mol% Li doping.     

Piezoelectric and mechanical properties of Pb(Zr0.52Ti0.48)O3–Pb(Y2/3W1/3)O3 (PZT–PYW) ceramics

The piezoelectric and mechanical properties of hot-pressed PZT–PYW were investigated. As the Pb(Y_2/3W_1/3)O₃ concentration increased, the piezoelectric constant (d ₃₃) also increased up to a concentration of 3 mol% PYW reaching a value of 485×10-12 CN^-1, but beyond this concentration it continuously fell. A decrease in grain size with increasing Pb(Y_2/3W_1/3)O₃ content in the system changed the transgranular fracture mode to an intergranular fracture mode, resulting in an enhancement in K _1c from 0.83 MPam^1/2 at 1 mol% PYW to 1.1 MPam^1/2 at 3 mol% PYW. Consequently, the highest d ₃₃ and K _1c values were obtained at the composition 0.97Pb(Zr_0.52Ti_0.48) O₃–0.03Pb(Y_2/3 W_1/3)O₃. This revised version was published online in November 2006 with corrections to the Cover Date.     

Pb(Zr0.95Ti0.05)O3粉体的冲击波合成及烧结研究

以ZrO2、Pb304和TiO2为原料（Nb2O5为掺杂剂）,采用柱面冲击波装置合成了Pb（Zr0.95 Ti0.05）O2（PZT95／5）粉体,并对粉体活性及其烧结性能进行了研究。XRD及SEM分析表明,利用冲击波的高温高压作用可以合成单一钙钛矿相PZT95／5粉体,并使得粉体发生了晶粒细化与晶格畸变,这有利于增强粉体活性,促进低温活化烧结。该粉体在1100℃的低温下即可烧结成瓷;在1200℃烧结3h,陶瓷体致密度达到最大,约7．79g／cm^3,且晶粒尺寸相近,分布均匀。     

Preparation and properties of Pb0.99Nb0.02(Zr0.52Ti0.48)0.98O3 by a new sol–gel technique

A new sol–gel processing technique has been developed for preparing Nb-doped lead zirconate titanate (PZT) with the composition Pb_0.99Nb_0.02(Zr_0.52Ti_0.48)_0.98O₃. The sol was prepared from Pb(NO₃)₂, NbCl₅, Ti(OC₃H₇)₄ and Zr(C₄H₉O)₄, dissolved in N, N-dimethyl-formamide with stirring at ambient atmosphere. The gel was calcined at 500 °C for 30 min and pressed pellets were sintered in air at 1000 °C for 2–20 h. The average grain size in the pellets sintered for 4 h was about 1.4 μm, which was smaller than that in undoped PZT pellets. Nb doping decreased angle α in the rhombohedral crystal structure, thereby enhancing electromechanical coupling. This revised version was published online in November 2006 with corrections to the Cover Date.     

Effect of strain on ferroelectric and magnetic behavior in Pb(Zr0.52Ti0.48)O3-based magnetoelectric heterostructures

In this paper, the "sandwich" structured magnetoelectric composite films of Pb(Zr0.52Ti0.48)O3/ NiFe2O4/Pb(Zr0.52Ti0.48)O3 and Pb(Zr0.52Ti0.48)O3/CoFe2O4/Pb(Zr0.52Ti0.48)O3 are epitaxially grown on SrRuO3/SrTiO3 substrates by pulsed-laser deposition. The crystalline quality and microstructures of these heterostructures are investigated by X-ray diffraction technique. The effects of strain on the ferroelectric, magnetic and magnetoelectric coupling properties of these thin films are systematically studied. The results show that the strain effect induced by lattice mismatch between the ferroelectric/ferromagnetic layers plays an important role in the ferroelectric and magnetic properties of these composite films. Compared to the strained Pb(Zr0.52Ti0.48)O3/ CoFe2O4/Pb(Zr0.52Ti0.48)O3 heterostructure, improved ferroelectric properties with an out-of-plane polarization (2P(r)) of 34.2 microC/cm2 and electric coercivity field of 158 kV/cm are obtained in the strain-free Pb(Zr0.52Ti0.48)O3/NiFe2O4/Pb(Zr0.52Ti0.48)O3 heterostructure. The ME measurement results not only show that the strain induced by lattice mismatch has great influence on the ME behavior, but also provide an understanding of the multilayers with full control over the interface structure at the atomic-scale.     

Pb(Zr0.52Ti0.48)O3 ceramics sintered with Li2CO3 and Na2CO3: improvement of characteristics

The electrical characteristics of PZT 52/48 and PZTN 52/48 could be improved with a pair doping method, i.e. by doping monovalent cation R⁺ with an equal amount of trivalent cation R³⁺. The doping pairs could promote the densification of the ceramics and provide charge compensation for the unbalanced charge arising from Li₂CO₂ or Li₂CO₃ doping. The pair doping method also released the problem of adding excess PbO for compensation of PbO evaporation in sintering and as liquid-phase former. Since the doping pair, such as the Li-Bi pair, could serve as a liquid-phase former, also, but with improved characteristics. If the samples were sintered under appropriate conditions, the obtained characteristics were comparatively process-insensitive. The optimal sintering conditions were at 1050‡ C for 2h. With the Li-Bi doping pair and sintered under these conditions, the PZTN 52/48 could have ak _p of about 60%, frequency constantN of about 1840 kHz mm,Q _m of about 255 andε ₃₃ ^T of about 1070.     

Enhanced magnetoelectric coupling in Pb(Zr0.52Ti0.48)O3 film-on-CoFe2O4 bulk ceramic composite with LaNiO3 bottom electrode

By chemically depositing a conductive LaNiO₃ (LNO) electrode layer onto dense CoFe₂O₄ (CFO) ceramics, the magnetoelectric (ME) response in Pb(Zr_0.52Ti_0.48)O₃ (PZT)/CFO film-on-substrate system was significantly enhanced. Structural, morphological, ferroelectric, and piezoelectric analysis was performed for the present PZT/LNO/CFO film-electrode-substrate composites, whereby improved electric-related output was demonstrated. It was further shown that the maximum ME coefficient α _E31 could reach up to 155 mV/cm Oe, which was about 2.6 times higher than that in PZT film-on-CFO ceramics without bottom electrode layer. Further enhancement of ME response could be expected by preparing high-quality electrode layer with optimal thickness and improved fabrication processing for such film-electrode-substrate composites.