Pyroelectric Crystals Crafted by Reduction in Symmetry and Their Functional Applications in Chemistry

Polar crystals, which display pyroelectricity and piezoelectricity, can serve as a useful tool in the research of solid-state chemistry. However, the strict requirements for the absence of prevalent symmetry elements in such crystals have limited their numbers and thus their possible applications in the field. Here, we report that by combining the method of crystal doping with “tailor-made” auxiliaries, one may convert nonpolar crystals into polar ones and thus investigate some of their concealed properties by electrical measurements. After a brief outline of the principles of pyroelectricity and the rational design behind dopant selection for each crystal, some functional applications are illustrated. This includes the following examples: (i) How alcohols induce the crystallization of the metastable β-polymorph of glycine in aqueous solutions. (ii) Pyroelectricity from surfaces that delineate nonpolar crystals. (iii) Engineering pyroelectric crystals depleted from piezoelectricity. (iv) The detection of enantiomeric disorder in crystal growth. (v) The discovery of a chemical cooperative mechanism of electro-freezing of supercooled water induced by “ice maker” species and electric fields.

Doping nonpolar crystals with “tailor-made” auxiliaries enables their transformation into polar crystals, facilitating studies of hidden properties through electrical measurements. This approach unlocks functional applications such as metastable polymorph formation, surface pyroelectricity, pyroelectricity with no piezoelectricity, enantiomeric disorder detection, and electro-freezing of supercooled water, expanding research avenues in solid-state chemistry and crystal engineering.