abstract
In the context of sensor, actuator, and energy harvesting applications, lead-free ferroelectric K0.5Na0.5NbO3 (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 K0.5Na0.5NbO3 ceramics: after annealing, both conventional and flash-sintered KNN ceramics exhibited electrically homogeneous behaviour similar to that of single crystals.
keywords
PIEZOELECTRIC PROPERTIES; DENSIFICATION; CERAMICS
subject category
Materials Science; Physics
authors
Tkach, A; Serrazina, R; Pereira, L; Senos, AMOR; Vilarinho, PM
our authors
Oleksandr Tkach
Principal Researcher
Paula Maria Lousada Silveirinha Vilarinho
Vice DirectorProjects
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
CICECO - Aveiro Institute of Materials (UIDP/50011/2020)
Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)
Collaboratory for Emerging Technologies, CoLab (EMERGING TECHNOLOGIES)
acknowledgements
This work was conducted within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 (DOI: 10.54499/UIDB/ 50011/2020), UIDP/50011/2020 (DOI: 10.54499/UIDP/50011/2020) & LA/P/0006/2020 (DOI: 10.54499/LA/P/0006/2020), financed by national funds through FCT/MEC (PIDDAC). This work was also financed by Portugal 2020 through the European Regional Development Fund (ERDF), under the Operational Competitiveness and Internationalization Programme (POCI), as part of the project "FLASH sintering of lead free functional oxides towards sustainable processing of materials for energy and related applications - FLASH", POCI-01-0247-FEDER-029078. FCT is acknowledged for the financial support by Ricardo Serrazina (SFRH/PD/BD/128411/2017) and Alexander Tkach (2021.02284.CEECIND (DOI: 10.544 99/2021.02284.CEECIND/CP1659/CT0018)).