Ultrafast high-temperature sintering of potassium-sodium niobate: Processing and properties

Current regulations pushing for lead-free piezoelectric alternatives have highlighted potassium-sodium niobate (K0.5Na0.5NbO3, KNN) as a promising candidate. However, conventional sintering of KNN faces challenges like alkali element volatilization and inadequate densification. Ultrafast high-temperature sintering (UHS) offers a solution by rapidly heating ceramics, yielding fine microstructures, with minimal volatile element loss. Here, using a custom UHS equipment we produced undoped KNN ceramics, identifying optimal sintering conditions via a UHS processing map. UHS KNN ceramics sintered for ≤90 s achieved 91 % density, <2 µm average grain size, and no secondary phases. This study reports also the first dielectric, piezoelectric, and ferroelectric properties of UHS KNN ceramics. Differences between as-UHS and post-annealed ceramics were observed as well, with the latter exhibiting piezoelectric coefficients of ~80pC/N. This research enhances understanding of UHS applications and potential of KNN for lead-free piezoelectric uses.