Improving Hydrogen Permeation Resistance in Ultrathin ZrO₂ Coating via Y Dopant Tuning

Ceramic coatings have recently found applications as efficient hydrogen permeation barriers (HPBs) in the development of hydrogen and nuclear energy. Finding a simple method to increase hydrogen permeation resistance is essential for HPB applications. Herein, we fabricated an ultrathin zirconia (ZrO₂) coating using a facile sol-gel technique and increased its hydrogen permeation resistance via yttrium (Y) dopant tuning. With 12 mol % Y doping, the hydrogen permeation resistance of the 50 nm-thick ZrO₂ coating increased 10-fold, reaching 1019 times that of the austenite steel substrate. The mechanism behind this notable improvement was elucidated based on insights into the Y-dependent microstructural evolution of the ZrO₂ coating. Below 8 mol %, the Y dopant dissolved in the ZrO₂ lattice, reducing grain size. Greater Y content (>12 mol %) caused yttria nanoparticles to precipitate, generating a heterogeneous interface within the ZrO₂ coating and remarkably maximizing its hydrogen permeation resistance. Notably, this Y-doped ZrO₂ coating exhibited high thermal shock resistance, maintaining an intact structure after 80 thermal shock cycles under 600 °C water cooling. Heterogeneous interface design via doping may offer a distinctive approach to developing high-performance ceramic coatings for use as HPBs.