Monitoring BaTiO3 sintering using nanosecond pulsed electric field

Abstract

Sintering is a critical process in ceramic fabrication, conducted in electric furnaces. However, the conditions within these furnaces remain largely unobservable, necessitating the development of real-time monitoring techniques. Conventional methods, such as thermal shrinkage measurement and X-ray analysis, present limitations including restricted applicability and prolonged measurement times. Therefore, this paper presents a novel sintering monitoring technique employing nanosecond pulsed electric fields. These fields, characterized by short pulse widths and high voltage, minimize thermal effects and prevent flash events. Sintered ceramics were fabricated using BaTiO₃, and nanosecond pulsed electric fields were applied during the heating, holding, and cooling phases. Herein, a nanosecond pulsed voltage of 1 kV, 500 ns, and 1 kHz was used. Current waveforms exhibited an increasing trend with temperature, with significant changes observed near 900 °C, coinciding with the onset of oxygen ion diffusion. Despite high current densities, no material damage or temperature increase was observed under these conditions. In conventional DC applications, Joule heating and flash phenomena occur. However, despite the application of high current density, no material damage or temperature increase was observed. Cross-sectional analysis revealed smaller grain boundaries at the sample centre and pore formation near the electrodes, suggesting that nanosecond pulsed electric fields regulate oxygen reduction and void diffusion without promoting grain growth. Furthermore, X-ray diffraction analysis confirmed no significant impact on the crystal structure. Unlike direct current fields, which lead to blackening during flash sintering, nanosecond pulsed electric fields induced partial discoloration owing to localized oxygen deficiencies. This unique behaviour stems from their ability to suppress heat generation while influencing sintering dynamics. Notably, the application of nanosecond pulsed electric fields enabled the use of an electric field of 6 kV cm− 1, exceeding previously reported values by up to a factor of 20. These findings demonstrate that nanosecond pulsed electric fields is a promising technique for monitoring and controlling sintering processes, offering new insights into their potential applications in advanced material design and manufacturing technologies.

Keywords

• In-situ
• Non-destructive evaluation
• electrical properties
• BaTiO3
• Methodology
• apparatus