Non-centrosymmetric (NCS) materials, those that do not contain an inversion center, exhibit a variety of important functional properties. These include, ferroelectricity, pyroelectricity, piezoelectricity, and second-harmonic generation. A Venn diagram depicting the relationships between acentric crystal class and physical property is shown below.
Our interest is in not only discovering new NCS materials, but also understanding their structure-property relationships. We have focused on synthesizing new NCS materials by utilizing cations susceptible to second-order Jahn-Teller (SOJT) distortions, i.e. octahedrally coordinated d0 transition metals (Ti4+, Nb5+, W6+, etc.), and cations with a stereo-active lone-pair (Sn2+, Se4+, Te4+, etc.). In doing so, we have synthesized and characterized a variety of new NCS compounds. More recently, we are focusing on NCS materials with deep UV NLO applications, i.e., where the absorption edge is less than 200nm. We have an ongoing collaboration with Prof. James Rondinelli (Northwestern University - http://mtd.mccormick.northwestern.edu/) to investigate the atomic distortions in these materials.