The paper discusses the stabilization mechanisms of pure tetragonal zirconia (t-ZrO2) nanocrystallites using an original supercritical-based synthesis route. The authors, Gilles Philippot, Aimery Auxemery, Cyril Aymonier, Denis Testemale, Jean-Louis F Hazemann, and Bo Iversen, explore how the crystallization pathways and kinetics of t-ZrO2 can be significantly influenced by variations in the synthesis medium and the ratio of metal nitrate to the complexing agent. They introduce a borderline nonhydrolytic sol-gel (B.N.H.S.G.) method, where small amounts of water molecules are generated in situ to control reaction kinetics and enable in situ total scattering measurements. These measurements, combined with various ex situ characterizations, help to understand the critical size below which pure t-ZrO2 forms and propose a formation mechanism for this specific synthesis route. The study highlights the importance of the initial gel structure in the overall crystallization behavior of the system.The paper discusses the stabilization mechanisms of pure tetragonal zirconia (t-ZrO2) nanocrystallites using an original supercritical-based synthesis route. The authors, Gilles Philippot, Aimery Auxemery, Cyril Aymonier, Denis Testemale, Jean-Louis F Hazemann, and Bo Iversen, explore how the crystallization pathways and kinetics of t-ZrO2 can be significantly influenced by variations in the synthesis medium and the ratio of metal nitrate to the complexing agent. They introduce a borderline nonhydrolytic sol-gel (B.N.H.S.G.) method, where small amounts of water molecules are generated in situ to control reaction kinetics and enable in situ total scattering measurements. These measurements, combined with various ex situ characterizations, help to understand the critical size below which pure t-ZrO2 forms and propose a formation mechanism for this specific synthesis route. The study highlights the importance of the initial gel structure in the overall crystallization behavior of the system.