On the border of chemical space: prediction of multianion inorganic systems Ln2OClFH2 (Ln = Y, La, Gd) with exceptional sensing characteristics

E. Strugovshchikov, A. Pishtshev
University of Tartu,
Estonia

Keywords: piezoelectric, sensors, energy harvesting, artificial skin, lead-free materials

Summary:

Playing with the distribution, configuration, interplay, and stability of the different anions in mixed-anion crystalline system one can effectively manage the structure-properties relationships in a generative way that takes into account a wide number of degrees of freedom. Within the frameworks of materials design this approach is very powerful because it presents unprecedented opportunities for accurate prediction of novel functional materials with targeted properties. In our research work, we modeled a polar solid that can be synthesizable with the mixed-anion composition Ln2OClFH2 (Ln = Y, La, Gd). Simulations of a virtual prototype of piezoelectric sensor showed that the use of this material may provide sensing characteristics greater than those of its competitors - advanced piezopolymers like PVDF systems. Moreover, such sensor device may also significantly outperform the functional usability of an electroactive elastomer with respect to the technologically known limit of operating temperatures. Based on the comparison of dielectric, piezoelectric and mechanical properties we emphasize three important features. First, the predicted inorganic compound Ln2OClFH2 can be classified as a solid-state material relating to the group of lead-free piezoelectric-semiconductors like ZnO and AlN among which it is characterized by the anomalously large values of the linear compression along the polar c-axis. Secondly, the material exhibits both high voltage sensitivity and remarkable piezoelectric output voltage. This implies that it may serve as the host compound for the development of the following devices: (i) transverse stress sensing elements for the control of applied mechanical loads, (ii) sensitive tactile sensors that might act in a range of external forces from 0.01 to 1000 N, and (iii) a responsive component of the artificial skin. The last feature is that due to highly-coupled elastic and electrical degrees of freedom the Ln2OClFH2-based system may be of particular interest as a functional unit of energy conversion systems. In this regard, we estimated the efficiency of energy harvesting for virtual sensor elements integrated into a hard road surface. In the case of transverse mechanical loads, our conceptual estimates of the piezoelectric harvesting power density showed that for Ln2OClFH2 this parameter may be about 5-10 times larger than that of commercially available PZT-5H and about 3-4 times larger than that of piezoelectric polymers.