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; 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：电容器是电子中的重要元素。一组氧化物材料通过改变其原子包装来响应电场，可以显示出极好的电容器应用特性。该项目利用先进的电子显微镜技术来揭示导致氧化物在纳米尺度上实时电响应的潜在微观结构机制。研究了机械应力对此类反应的影响。开发并应用了一种新的成像技术来对比材料的原始结构和变化的原子结构。预计工作的结果有助于为有效的电容器设计新材料，这些材料在可再生能源和电动汽车中迫切需要。在该项目中，包括教育活动，以将本科生，尤其是来自代表性不足的群体的学生整合到研究中。此外，研究小组向访问爱荷华州立大学的高中生参加了年度科学碗区域比赛的高中学生进行有关电容器的演示。技术描述：用抗纤维电材料作为电介质层可以使用超高的能量。据认为，在下一代电力电子中实施这种抗抗氟电容器可以提高其结构稳定性和能源效率。通过反复的抗抗铁电 - 铁相变，可以实现抗铁电容器中的超高能密度，这仅通过迄今为止极化和菌株的宏观表征来研究。这项研究工作旨在直接使用PI组开发的唯一原位透射电子显微镜技术，在纳米空间分辨率下，在纳米空间分辨率下，在纳米空间分辨率下，在纳米空间分辨率下，新阶段在纳米空间分辨率下新阶段的成核和生长演变。研究了晶体学取向和结构缺陷（例如位错和晶界）对成核过程的影响。此外，电子全息技术用于确定极性铁电相的极化方向，并将其与非极性抗抗抗抗逆抗抗逆抗阶段进行比较。这种对相转换的基本理解对于在未来电力电子中成功实施抗抗逆电能力至关重要。