Unveiling the electrical performance of flash-sintered potassium sodium niobate

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2024-10, Vol.12 (41), p.16958-16968
• Main Authors: Tkach, Alexander, Serrazina, Ricardo, Pereira, Luis, Senos, Ana M. O. R, Vilarinho, Paula M
• Format: Article
• Language: English
• Subjects: Actuators; Budgets; Ceramics; Crystal defects; Curie temperature; Electric fields; Electrical properties; Electrical resistivity; Energy harvesting; Ferroelectric materials; Ferroelectricity; Heat treatment; Impedance spectroscopy; Lattice vacancies; Lead free; Piezoelectricity; Resistance sintering; Sintering; Spectrum analysis; Transition temperature
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d4tc01702a

In the context of sensor, actuator, and energy harvesting applications, lead-free ferroelectric K 0.5 Na 0.5 NbO 3 (KNN) ceramics offer several advantages, including a high transition temperature and an elevated piezoelectric coefficient. However, producing single-phase KNN ceramics at a low thermal budget requires alternative sintering processes such as electric-field- and current-assisted flash sintering. Furthermore, the electrical properties of flash-sintered ferroelectrics are rarely disclosed. Here, based on systematic dielectric and ferroelectric, impedance spectroscopy and DC conductivity measurements, we demonstrate that the electrical performance of flash-sintered KNN is quite dependent on its thermal history, in contrast to the conventionally sintered one. Simultaneously, we demonstrate the successful production of high-performance KNN ceramics with high polarization, dielectric permittivity, Curie temperature, and piezoelectric coefficient using flash sintering, coupled with a carefully chosen post-sintering electrode curing step. Supported by impedance spectroscopy results, indicative of enhanced oxygen vacancy content in flash-sintered KNN, we postulate that post-sintering heat treatment and low-thermal-budget flash sintering are equally critical for KNN applications, complementing the benefits of reducing lattice defects and enhancing electroceramic performance. Our results demonstrate a pathway towards alternative sintering of electroceramics and offer opportunities to control performance. Electrical performance of flash-sintered K 0.5 Na 0.5 NbO 3 ceramics: after annealing, both conventional and flash-sintered KNN ceramics exhibited electrically homogeneous behaviour similar to that of single crystals.