R. Ristic et al., GROWTH OF THE TETRAHEDRAL FACES OF SODIUM-CHLORATE CRYSTALS IN THE PRESENCE OF DITHIONATE IMPURITY, Journal of crystal growth, 139(3-4), 1994, pp. 336-343
It has been established that trace amounts of S2O62- anions initiate t
he appearance of new faces, {111BAR}, on sodium chlorate crystals grow
n from aqueous solution. The present study compares the growth mechani
sms of the {111} habit faces and {111BAR} type faces using laser inter
ferometry techniques. The {111} faces show dislocation layer growth in
which the impurity influences the growth by causing the gradual decel
eration of step movement. In contrast, the {111BAR} faces incorporate
crystal units into an atomically rough surface. Under these circumstan
ces the impurity on the surface creates a barrier to continuous growth
. The strong impurity interaction with the {111BAR} faces can be expla
ined by the close structural similarity of the -SO3 portion of the S2O
62- ions to the ClO3- ions situated on these faces. This allows the di
thionate ion to substitute for ClO3-, disturbing the structure and ene
rgy of the interface and inhibiting growth.