A hydration chamber for La-doped ceria ceramics with crystal hydrate-stabilized water vapor pressure

Conventional methods for hydrating bulk ceramic samples at relatively low pressures (<5 atm of water steam) often fail to achieve significant hydration because of kinetic barriers and mechanical failures, the latter primarily due to inhomogeneous lattice expansion accompanying hydration. We propose a small, high-pressure chamber that can reach tens of atm of steam pressure without the necessity of operating a high-pressure/high temperature autoclave or pressure vessel. The chamber takes advantage of the dehydration of CoSO₄·7H₂O powder to stabilize water partial pressure up to 100 atm. This facilitates effective hydration at moderate temperatures, producing crack free pellets under reproducible conditions. Using La 0.45 Ce 0.55 O 1.775 ceramics (LCO45) as a test case, we demonstrate that hydration in the chamber with P H 2 O ≈ 56 atm produces at least ten times more water incorporation than hydration with 1 atm steam (38.5 % vs 3.7 % of oxygen vacancies filled) at the same temperature, 673 K, while requiring approximately one-tenth of the time (5 h vs 48 h). X-ray powder diffraction reveals an expansion of 0.43 % in the fluorite lattice parameter of LCO45 ceramics hydrated in the chamber. Chamber hydration increased conductivity in the temperature range 383–463 K by ca. two orders of magnitude compared to the dry pellet, the increase attributable to proton conductivity. The hydration protocol described below does not allow independent setting of temperature and pressure; however, due to its simplicity and economic accessibility, it may provide a viable method for achieving a high degree of hydration in ceramic samples while, at the same time, preserving their mechanical integrity. • A high-pressure chamber (pressure vessel) for hydration of ceramics is proposed. • Pressure in the chamber is stabilized by CoSO₄·7H₂O. • The chamber was successfully used to hydrate La0.45Ce0.55O1.775 ceramics. • Water vapor pressure in the chamber was 56 atm at 673 K. • TGA measurements found that 38.5 % of oxygen vacancies were filled.