Atmospheric-Pressure Plasma Jet Treatment Triggers Early Sintering-Related Microstructural Changes in 3Y-TZP Green Body

To evaluate whether atmospheric-pressure plasma jet (APPJ) treatment induced early, sintering-related, surface microstructural variations in 3 mol% yttria-stabilized zirconia (3Y-TZP), with a particular focus on how treatment time affected the grain size and SEM-derived surface dark-area fraction, this exploratory study examined time-dependent surface microstructural changes in commercial 3 mol% yttria-stabilized zirconia (3Y-TZP) subjected to air APPJ exposure for 4, 8, 15, 30, or 60 min under fixed device settings. A separate no-dwell furnace reference series was used to contextualize surface microstructural changes during heating; it was not used to assign an equivalent temperature to APPJ exposure. Field-emission scanning electron microscopy was used to determine surface grain dimensions and a threshold-derived surface dark-area fraction. No specimen-surface temperature was recorded during APPJ exposure. Surface grain dimensions remained similar through 15 min and increased at 30 and 60 min, whereas the surface dark-area fraction changed modestly. Under the tested conditions, prolonged APPJ exposure was associated with marked surface grain coarsening and limited change in the SEM-derived dark-area fraction.