EFFECT OF POST-PRECIPITATION TREATMENT ON THE PORE-STRUCTURE STABILITY OF SOL-GEL-DERIVED LANTHANUM ZIRCONATE

The importance of post-precipitation treatments (pore-fluid exchange a nd its removal) on the evolution of the texture of coprecipitated lant hanum zirconate has been investigated, The nature of the pore fluid an d the type of fluid-removal (drying) process have shown a profound eff ect on the aggregate structure (packing of primary particles within th e aggregates of the gel), Exchanging the pore fluid with organic fluid s such as ethanol or tetrahydrofuran resulted in higher specific surfa ce area, larger pore volume, and, most frequently, larger pore radii. The effect has been attributed to the surface tension of the pore flui d rather than to the polycondensation effect. Freeze drying and microw ave drying of ethanol-mashed lanthanum zirconate gel also resulted in higher surface area, compared to the oven-dried gel. Freeze drying and microwave drying yielded a surface area of similar to 30 m(2)/g, g wh ereas oven drying yielded a surface area of 20 m(2)/g after heating at 800 degrees C.