Earth-grown crystals

Ng, J.D., et al., Comparative analysis of space-grown and earth-grown crystals of... 

Figure 3. Photograph of Earth Grown Crystals, Showing Half Coverage of Membrane...

Another interesting observation of the earth grown crystals is that nucleation only occurs on the membrane or on crystals that are attached to the membrane. This may have to do with intergrowth and twinning of the original crystals. In time, some of the crystals fall to the bottom of the reactor due to gravitational effects. 

CHARACTERIZATION OF LEAD IODIDE CRYSTALS. The AES data of Figure 4 suggest that very pure crystals of lead Iodide were grown in the shuttle. The amount of carbon contaminant is appreciably lower than the earth grown crystals (Figure 5) and the ratio of iodide to lead is much closer to the ideal ratio of 2 for the shuttle grown crystals than the earth grown materials. 

The crystal growth of lead iodide in space and on earth is the subject of this paper. All materials were characterized on earth although the growth mechanism was filmed at both locations In order to better understand differences between earth and space grown crystals. 

Figure 5. Auger Electron Spectrum of Earth Grown Lead Iodide Crystals...

The appearance of a shelf of crystals with the earth grown lead iodide crystals may indicate that the different ions are mixing near this level of the tube. It may be possible that crystals are nucleating above this level and then falling down to this level where they attach to other crystals and to the membrane. 

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