Influence of Reaction Medium on Formation of Nanocrystalline YSZ Prepared by Conventional and Modified Solvothermal Process

8 mol% yttria stabilized zirconia (8YSZ) nanopowders have been synthesized via a co-precipition-solvothermal treatment process at 200oC for 2-48 h. The co-precipitated amorphous hydroxide precursors were obtained by adding rare earth nitrate solution in an ammonia solution. Then the hydroxide precursors were solvothermal treated in various reaction media namely water, ammomia soluion and ethanol, followed by drying at 80oC over night . The influence of reaction medium on crystallzation and agglomeration state of 8YSZ nanopowders were investigated using XRD, SEM, and BET. Correlation between dielectric constant, boiling point and surface tension of reaction medium with crystallization and morphology of as-synthesized powders were discussed. The crystallization rate could be accelerated with the use of a low boiling point reaction medium. Crystallite size was increased with increasing dielectric constant and reaction time. The agglomeration state during drying process strongly depended on surface tension of the reaction medium. Improvement of agglomeration of primary particles was also proposed. The average crystallite sizes from all conditions were lower than 10 nm.