Growth Units and Formation Mechanisms of the Crystals Under Hydrothermal Conditions

The growth units and formation mechanisms of quartz（SiO2）and barium titanate（BaTiO3）crystals under hydrothermal conditions have been investigated by means of cataphoretic experi-ments.It is proposed that the growth units of the crystals in hydrothermal solutions have the structuresof coordinative polyhedra of anions,which correspond to those of coordinative polyhedra in the crystals.The relationship between crystal morphology and physico-chemical conditions has been explained accord-ing to the modes of incorporation of the coordinative polyhedra of anions on the various faces of crystals.The dimensions of the growth units vary with the change of the growth condition.The incorporation rateson the various faces of the growth units with varied dimensions must be different,which leads to a satis-factory explanation for the variety of the crystal morphology.