Nanoscale Phase Transition in Free-Standing Dielectric Thin Foils

独立式电介质薄箔中的纳米级相变

• 批准号: 1700014
• 负责人: Xiaoli Tan
• 金额: $ 39.62万
• 依托单位: Iowa State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-07-01 至 2022-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1700014&HistoricalAwards=false
• 关键词: Nanoscale; Phase; Transition; Free; Standing

Non-technical description: Capacitors are essential elements in electronics. A group of oxide materials responding to electric fields by changing their atomic packing arrangements can display excellent properties for capacitor applications. This project utilizes advanced electron microscopy techniques to reveal the underlying microstructural mechanisms responsible for the electrical responses of the oxides at the nanometer scale in real time. The impact of mechanical stresses to such responses are examined. A new imaging technique is developed and applied to contrast the material's original and changed atomic structures. The outcome of the work is expected to be helpful in designing new materials for efficient capacitors, which are urgently needed in renewable energy sources and electric cars. In this project, educational activities are included to integrate undergraduate students, especially those from underrepresented groups, into the research. In addition, the research team presents demonstrations on capacitors in smart phone chargers to high school students visiting Iowa State University for the annual Science Bowl regional competition. Technical description: Ultrahigh energy capacitors are possible with antiferroelectric materials as dielectric layers. It is believed that implementation of such antiferroelectric capacitors in the next generation power electronics could improve their structural stability and energy efficiency. The ultrahigh energy density in antiferroelectric capacitors is achieved through repeated antiferroelectric - ferroelectric phase transition, which has only been investigated through macroscopic characterization of polarizations and strains so far. This research effort aims to directly visualize the nucleation and growth evolution of the new phase during this critical phase transition at nanometer spatial resolution in free-standing thin foils of antiferroelectric oxides using a unique in situ transmission electron microscopy technique developed by the PI's group. The influences of crystallographic orientation and structural defects, such as dislocations and grain boundaries, on the nucleation process are examined. In addition, electron holography technique is applied to determine the polarization direction of the polar ferroelectric phase, and to compare it with the nonpolar antiferroelectric phase. Such fundamental understanding of the phase transition is of critical importance for the successful implementation of antiferroelectric capacitors in future power electronics.

非技术描述：电容器是电子器件的基本元件。一组通过改变其原子排列来响应电场的氧化物材料可以在电容器应用中显示出优异的性能。该项目利用先进的电子显微镜技术，实时揭示了纳米级氧化物电响应的潜在微观结构机制。研究了机械应力对这种反应的影响。开发了一种新的成像技术，并应用于对比材料的原始和变化的原子结构。这一成果有望为可再生能源和电动汽车急需的高效电容器新材料的设计提供帮助。在这个项目中，教育活动包括将本科生，特别是那些来自代表性不足群体的本科生纳入研究。此外，研究小组还向访问爱荷华州立大学参加年度科学碗地区竞赛的高中生展示了智能手机充电器中的电容器。技术描述：用反铁电材料作介电层可制成超高能电容器。研究人员认为，在下一代电力电子器件中应用这种反铁电电容器可以提高其结构稳定性和能效。反铁电电容器的超高能量密度是通过反复的反铁电-铁电相变来实现的，迄今为止只通过极化和应变的宏观表征来研究。这项研究的目的是利用PI小组开发的一种独特的原位透射电子显微镜技术，在纳米空间分辨率下，在独立的反铁电氧化物薄箔中，直接观察临界相变期间新相的成核和生长演变。研究了晶体取向和结构缺陷（如位错和晶界）对成核过程的影响。此外，利用电子全息技术确定了极性铁电相的极化方向，并将其与非极性反铁电相进行了比较。这种对相变的基本理解对于未来电力电子中反铁电电容器的成功实现至关重要。

项目成果

Atomically resolved domain boundary structure in lead zirconate-based antiferroelectrics

• DOI: 10.1063/1.5115039
• 发表时间: 2019-09
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: T. Ma;Z. Fan;X. Tan;Lin Zhou

Motion of phase boundary during antiferroelectric–ferroelectric transition in a PbZrO3 -based ceramic

• DOI: 10.1103/physrevmaterials.4.104417
• 发表时间: 2020-10
• 期刊: Physical Review Materials
• 影响因子: 3.4
• 作者: Binzhi Liu;Xinchun Tian;Lin Zhou;X. Tan

TEM investigation of the domain structure in PbHfO3 and PbZrO3 antiferroelectric perovskites

• DOI: 10.1007/s10853-020-04361-8
• 发表时间: 2020-01
• 期刊: Journal of Materials Science
• 影响因子: 4.5
• 作者: Z. Fan;T. Ma;Jing Wei;T. Yang;Lin Zhou;X. Tan

In situ TEM observation on the ferroelectric‐antiferroelectric transition in Pb(Nb,Zr,Sn,Ti)O 3 /ZnO

• DOI: 10.1111/jace.18148
• 发表时间: 2021-10
• 期刊: Journal of the American Ceramic Society
• 影响因子: 3.9
• 作者: Binzhi Liu;Ling Li;Shantao Zhang;Lin Zhou;X. Tan

Structure, ferroelectric, and dielectric properties of (Na1−2xCax)NbO3 ceramics

• DOI: 10.1557/s43578-020-00020-5
• 发表时间: 2021-01
• 期刊: Journal of Materials Research
• 影响因子: 2.7
• 作者: Binzhi Liu;X. Tan