Inhibitory Phenomena of Crystal Growth of Inorganic Phosphorus Compounds by Admixture Impurities

Abstract

The presence of impurities in the process of industrial crystallization influences crystal growth phenomena and often dominates production efficiency. The present work was therefore undertaken to study how the presence of impurities (admixture impurities) influences growth phenomena of single crystals and crystalline particles (suspended crystals) of inorganic phosphorus compounds, and how admixture impurities influence the quality of crystalline particles.
We found that admixture impurities affect crystal growth rate but not crystal structure. In particular, Ca²⁺ had a greater influence on crystal growth rate than other metal ions, and the addition of Ca²⁺ at an ionic concentration of 10 ppm (solution mass ratio) caused a decrease of about 35% in the crystal growth rate. Furthermore, crystal growth rate could be recovered by the addition of a masking agent, EDTA, even in the presence of Ca²⁺. Thus, we found an indicator to improve production efficiency of crystalline particles in the presence of admixture impurities.