Continuous precipitation of yttrium hydroxycarbonate spheres of narrow size distribution

Submicron spherical particles of the yttria precursor Y(OH)CO3·H2O were continuously precipitated in three types of reactors: mixed-suspension mixed-product removal (MSMPR); semi-batch; and packed bed. The homogeneous precipitation occurred as a result of the thermal decomposition of urea in an aqueous yttrium nitrate solution. A wide variety of particle size distributions were produced from these reactors. Mathematical models, which assumed that particle growth was by a diffusion mechanism, successfully allowed the size and shape of the particle size distributions to be predicted and controlled. It was shown that the concentration of the rate-limiting diffusing species could be calculated from a simple analysis of the particle size distribution from the MSMPR reactor. From such as analysis, it appeared that carbonate was the rate-limiting diffusant