Growth of sodium chlorate crystals in the presence of potassium sulphate

• The morphology of crystals changes from cubic to tetrahedral in the presence of K2SO4.
• Growth of NaClO3 crystals is noticeably retarded in solutions with K2SO4 additives.
• The {110} face is the most and the {100} face is the least inhibited by SO42−.
• The mechanism of K2SO4 action is adsorption of SO42− ions on crystal surfaces.
• Atomic structure and charge state of the faces determine their sensitivity to SO42−.

In this work, we investigated the morphology and growth rates of NaClO3 crystals in solutions with K2SO4 additives. NaClO3 crystals were grown using the temperature gradient technique under concentration convection. We found that the crystal habitus changed from cubic to tetrahedral, and the growth of the cubic {100}, tetrahedral {111} and rhomb-dodecahedral {110} faces decelerated with an increase in the concentration of SO42− ions. The {110} face was the most and the {100} face was the least inhibited by sulphate ions. The mechanism of SO42− ions action is their adsorption on the crystal surface, which impedes attachment of the crystal׳s building units. We conclude that different atomic structure and charge state of various crystal faces determine their sensitivity to the action of the SO42− ions.