Chemistry

Lead-Free Film

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Science  18 Apr 2014:
Vol. 344, Issue 6181, pp. 237
DOI: 10.1126/science.344.6181.237-c
CREDIT: REN-GEN XIONG

Ferroelectric materials have a permanent electric dipole moment that can be switched by the application of an external electric field, a property that makes them widely used in sensing, memory, and actuators. Most commonly used ferroelectrics are perovskites, such as lead zirconium titanate (PZT). Molecular ferroelectrics present an interesting, more environment-friendly alternative, but in the technologically relevant thin-film form they have been found to perform considerably more poorly than in bulk. Zhang et al. find that imidazolium perchlorate is a molecular ferroelectric with relatively high spontaneous polarization and transition temperatures. The authors grow films of this material by depositing it on a substrate by the spin-coating method, and induce dendritic crystal growth on the surface by placing it in a saturated solution. The resulting films show properties comparable to those of the bulk material and, in addition, their piezoelectric response, relevant to applications and measured by piezoresponse force microscopy, compares well to those of films of the more established ferroelectrics such as PZT.

Angew. Chem. Int. Ed. 10.1002/anie.201400348 (2014).

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