CORRELATION BETWEEN PYROELECTRICITY AND ALIGNMENT OF INTERFACIAL WATER

In this work we present two examples of connection between arrangement of water molecules pyroelectricity. Before the current work, pyroelectricity, the creation of a temporary surface charge upon temperature change, was attributed only to polar materials. Nevertheless, nonpolar Amino acid crystals, like a-glycine, and cubic Yttrium doped Barium Zirconate ceramics exhibit pyroelectricity. Experimental results together with MD simulation suggest that the source of this pyroelectricity is polar arrangement of water at the crystal surface, which leads to the formation of a deformed polar layer in the crystal itself. The fact that surface pyroelectric measurement can give a new information on the arrangement of water and reconstruction of different surfaces makes it an important surface characterization tool. Another phenomenon suggests that the converse effect, i.e. alignment of water by pyroelectricity, is also exists. Our group has demonstrated that polar crystals in general and specific positive pyroelectric charge can catalyze the freezing of super cooled water (SCW). Our studies show that pyroelectric effect increases the freezing point of SCW by 2 to 8 degrees. The fact that the freezing temperature was found to be correlated to the amount of the surface charge together with the relative low electric field (<10³ V/cm), implying that the surface charge alignments the interfacial water molecules or stabilizes sub-critical ice nuclei.

References:

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