Influence of defect chemistry on ferroelectric properties of KNN

缺陷化学对KNN铁电性能的影响

• 批准号: 419400593
• 负责人: Professor Dr. Karsten Albe
• 金额: --
• 依托单位: Fachgebiet Nichtmetallisch-Anorganische Werkstoffe
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/419400593?language=en
• 关键词: Influence; defect; chemistry; ferroelectric; properties

The lead-free ferroeletric ceramic (K0.5Na0.5)NbO3 (KNN) stands out because of its high piezoelectric coefficient d_33, excellent strain properties, high Curie Temperature T_C and mechanical quality factor Q_m. Despite the optimized and promising properties, KNN is rarely found in applications so far. This can be mainly attributed to the comparably high leakage currents and low density. The high leakage currents often result from extrinsic and intrinsic point defects. It was assumed that the knowledge from point defect thermodynamics on lead-based ceramics can be directly transferred to the lead-free material. This is, however, not the case. For example, in case of (Na1/2Bi1/2)TiO3 extremely high oxygen ionic conductivity instead of ferroelectric hardening was found for acceptor doping by Li et al. For KNN, doping strategies usually have a far lower impact on ferroelectric properties as it could be expected from the experience with lead-containing material. Interestingly, defect chemical investigations have recently also been conducted on lead-based ceramics to elucidate aging and degradation mechanisms. Thus it is of high importance to determine the defect chemical properties of lead-free ceramics right from the beginning to rationalize whether high reliability criteria can be fulfilled. A combination of experimental investigations based on conductivity experiments and quantum mechanical modelling will lead to a description of the influence of different dopands on KNN. Furthermore, the effect of microstructure and phase transitions will be taken into account to separate these from changes in defect chemistry. The ferroelectric properties will be determined as a function of height and application duration of electrical field. This way possible degradation and aging phenomena due to migrating defect species can be elucidated.

无铅铁培养陶瓷（K0.5NA0.5）NBO3（KNN）由于其高压电系数D_33，出色的应变特性，高咖喱温度T_C和机械质量Q_M而脱颖而出。尽管具有优化和有希望的特性，但到目前为止，在应用中很少发现KNN。这主要归因于相对高的泄漏电流和低密度。高泄漏电流通常是由外在和内在点缺陷引起的。假定可以将基于铅陶瓷的点缺陷热力学的知识直接转移到无铅材料中。但是，情况并非如此。例如，在（Na1/2bi1/2）TiO3的情况下，Li等人发现了极高的氧离子电导率，而不是铁电力硬化，而不是铁电力硬化。对于KNN而言，掺杂策略通常对铁电特性的影响要低得多，这可以从含铅材料的经验中预期。有趣的是，最近对铅基陶瓷进行了缺陷化学研究，以阐明衰老和降解机制。因此，从一开始就确定无铅陶瓷的缺陷化学特性至关重要，从而使是否可以满足高可靠性标准。基于电导率实验和量子机械建模的实验研究的组合将导致描述不同多潘德对KNN的影响。此外，将考虑微观结构和相变的影响，以将这些影响与缺陷化学的变化分开。铁电特性将被确定为电场的高度和应用持续时间的函数。这样，就可以阐明由于迁移缺陷物种而导致的降解和衰老现象。