MORPHOLOGY OF GEL-GROWN BARIUM CARBONATE AGGREGATES - PH EFFECT ON CONTROL BY A SILICATE-CARBONATE MEMBRANE

We have examined in detail the formation of induced morphology crystalline aggregates (IMCAs) of barium carbonate in the presence of silica at high pH. We find a gradation in form with pH, from dendritic through sheet-like and spiral to more complex. Using SEM with EDX and Rutherford back-scattering, and ESCA, we show that the growth process is governed by a barium carbonate-silicate phase overlying the barium carbonate and controlling its development. This is a special and extreme case of control of growth habit by adsorbed additives.