| Summary: | Rod-shaped barium sulfate particles can be formed from purely inorganic systems at 75 1C and theseparticles are single crystals elongated in the c-axis. This c-axis growth promotion relative to the othercrystal faces is absent when the cation impurities are absent suggesting a specific interaction of thecations with the growing crystal. Attempts have been made to determine the cause of this c-axisgrowth promotion, but no one mechanism appears to adequately explain this effect and it may be dueto a combination of different impacts. The same cations do not induce rod-shaped particles at 25 1C,thus suggesting an important role of kinetics in the crystallization of these particles. Finally, previousreports suggesting that the formation of rod-like particles is due to the presence of an organic additivemay be incorrect as sufficient sodium ions may have been present to give these particles even in their absence.
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