EAPSI: In situ Structural Characterization of Lead-free, Bismuth-based Piezoelectric Thin Films

EAPSI：无铅、铋基压电薄膜的原位结构表征

• 批准号: 1713806
• 负责人: Austin Fox
• 金额: $ 0.54万
• 依托单位: Fox Austin
• 依托单位国家: 美国
• 项目类别: Fellowship Award
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-06-01 至 2018-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1713806&HistoricalAwards=false
• 关键词: EAPSI; situ; Structural; Characterization; Lead

There is a pressing need to discover and understand the behavior of environmentally benign, non-toxic, and sustainable replacements for lead-based materials in all applications (as already has been done for lead-based paints and solders). Suitable replacements have yet to be realized for piezoelectric materials (those that change shape with applied electric field and vice versa) that are important for a large range of devices and applications, such as actuators, accelerometers, filters, vibration control, fuel injection, ink jet printing, ultrasound generation and sensing, and resonators. One class of materials that shows great promise as replacements is based on bismuth sodium titanate (BNT). In thin films for microelectronic applications, the fundamental piezoelectric effect in these new materials is not yet understood well enough to allow devices to be reliably implemented. Accordingly, the objective of this project is to explore the mechanisms associated with piezoelectricity in BNT-based piezoelectric thin films using novel characterization methods available at Professor Hiroshi Funakubo's laboratory at the Tokyo Institute of Technology. Professor Funakubo's characterization tools allow for the measurement of atomic structure while applying electric fields, giving direct insight into the piezoelectric strain mechanisms of these exceptional materials.In bulk form, these BNT-based materials belong to a class of materials called relaxor ferroelectrics, which show enticing properties with regards to electric field induced displacement mechanisms that are just beginning to be understood. Many BNT-based compositions show the strain and polarization behavior that is characteristic of a reversible field-induced relaxor-to-ferroelectric phase transition; these are known as ergodic relaxors. However, BNT-based materials in thin film embodiments do not exhibit the enhanced properties that are found in the bulk. In particular, the ergodic relaxor compositions that have been studied in thin films do not show the signs of a reversible field-induced relaxor-to-ferroelectric phase transition, but rather behave similar to normal ferroelectrics and have comparatively low displacements. This differing response between bulk and thin films needs to be understood for this promising material system to be viable for real-world applications. Therefore, novel in situ microstructural characterization methods (2D X-ray diffraction and Raman spectroscopy), available at the host institution, will be applied to elucidate the electric field induced strain mechanisms in BNT-based piezoelectric thin films.This award under the East Asia and Pacific Summer Institutes program supports summer research by a U.S. graduate student and is jointly funded by NSF and the Japan Society for the Promotion of Science.

迫切需要在所有应用中发现和了解对环境无害、无毒且可持续的铅基材料替代品的行为（就像对铅基油漆和焊料所做的那样）。压电材料（那些随着施加的电场而改变形状的材料，反之亦然）尚未实现合适的替代品，压电材料对于各种设备和应用都很重要，例如执行器、加速度计、滤波器、振动控制、燃料喷射、喷墨打印、超声波生成和传感以及谐振器。一类有望作为替代品的材料是钛酸铋钠 (BNT)。在微电子应用的薄膜中，这些新材料的基本压电效应尚未得到充分理解，无法可靠地实现器件。因此，该项目的目标是利用东京工业大学 Hiroshi Funakubo 教授实验室提供的新颖表征方法，探索与 BNT 基压电薄膜中的压电性相关的机制。 Funakubo 教授的表征工具允许在施加电场时测量原子结构，从而直接了解这些特殊材料的压电应变机制。在块状形式中，这些基于 BNT 的材料属于一类称为弛豫铁电体的材料，它在电场引起的位移机制方面表现出诱人的特性，而这些特性刚刚开始被理解。许多基于 BNT 的组合物表现出应变和极化行为，这是可逆场诱导弛豫剂到铁电相变的特征；这些被称为遍历松弛剂。然而，薄膜实施例中的基于BNT的材料并未表现出在本体中发现的增强的特性。特别地，已经在薄膜中研究的遍历弛豫剂组合物没有表现出可逆场诱导的弛豫剂到铁电相变的迹象，而是表现出与普通铁电体相似的行为并且具有相对较低的位移。需要理解块状薄膜和薄膜之间的这种不同响应，才能使这种有前景的材料系统在实际应用中可行。因此，主办机构提供的新型原位微观结构表征方法（二维 X 射线衍射和拉曼光谱）将用于阐明 BNT 基压电薄膜中的电场诱导应变机制。该奖项属于东亚和太平洋夏季研究所计划，支持美国研究生的夏季研究，由 NSF 和日本科学促进会共同资助。