Résumé
Hf1-xYxO2-x/2 ceramics have been recently suggested as a solid electrolyte for potentiometric sensors monitoring oxygen in liquid sodium. High density ceramics can be produced by an innovative dropwise wet-process using hydroxide coprecipitation allowing a homogeneous mixture of hafnium and yttrium under specific stoichiometric conditions in the presence of ammonia. Different parameters such as the synthesis duration (2–26 min), concentration (2–10 M) and excess of ammonia (200–1000 %) used were varied to determine the optimized synthesis parameters for obtaining a very dense material. After synthesis, the precursor obtained was mainly characterized by BET and then calcined under air at 700 °C to obtain the corresponding oxide. The latter was further characterized by BET, SEM, EDS and TGA before being shaped and sintered at 1600 °C. The relative density of the densest ceramics reached 97.6 ± 0.5 % of the theoretical density, rarely obtained by wet chemistry routes.
•The ammonia excess has a crucial impact on final density of the ceramics.•The existence of local pH conditions is found to be a key parameter to form mixed hydroxides.•The presence of mixed hydroxides enables a better sintering capability and densification.•The optimal parameters to obtain dense ceramics by wet route are determined.