Growing crystals
The specific properties of crystals make them key materials for a large number of technological fields such as electronics, communications, energy, medicine and defence. For all of these areas, it is of paramount importance to have crystals with the appropriate properties, size and quality. Crystal growth has become a major technological challenge.
Synthetic quartz crystals.Source: Coll. LMGP-Grenoble-INP
Crystallisation
Crystallisation is based on a simple principle: forming a solid object with atoms that are organised in a periodic array. This organisation is spontaneous but time must be allowed for it to take place and that time varies according to the crystals you are trying to grow.Take your time to make large crystals
When a molten compound is suddenly cooled (quenched) there is no long-range order of the positions of atoms (amorphous glass) as there was in the molten state. If cooling is sufficiently "slow", then the atoms and molecules have time to move and thus optimise their interactions and compactness. These two factors lead to an atomic order which is regularly repeated, and which will be propagated to new molecules/atoms joining those already solidified. Each atomic "layer" reproduces the order of the inner layer and acts as a model or "pattern" for the following ones.The period of time may vary considerably according to each material. If you want to grow a few large crystals instead of many small crystals, you'll need more time!
Surface of a biological crystal showing stacking faults as seen by atomic force microscopy.©l IUCr Journals
Recrystallisation of citric acid viewed under polarized light.
© CNRS Foteca / A. Jeanne-Michaud