• In-situ synchrotron X-ray imaging reveals three distinct bubble growth modes in LPBF of oxide ceramics: uplift growth, gas channel attachment, and bubble coalescence.
• Bursting of large bubbles induces melt flow oscillations, leading to local instability of the melt pool and potential pore formation.
• Understanding bubble dynamics provides critical insights for optimizing LPBF parameters to eliminate porosity and enhance mechanical properties of oxide ceramics.
• The study directly links bubble behavior to melt pool instability, offering a pathway to reduce defects in additively manufactured ceramics.