Permanently Polarized Materials: An Approach for Designing Materials with Customized Electrical Properties

The development of experimental procedures to transform conventional materials into new materials with unique properties has become a necessity in many fields, as for example catalysis, electronics, electrochemistry and biomedicine, among others. In recent years, the thermal stimulated polarization (TSP) treatment, which consists of applying a constant voltage at a high temperature, has been applied to hydroxyapatite, Ca 5 (PO 4 ) 3 OH (HAp), leading to permanently polarized HAp (p-HAp). The enhanced electrical properties of p-HAp, which are the consequence of the controlled generation of vacancies, the specific orientation of the remaining OH – groups and the surface charge accumulation have been used for the catalytic fixation of CO 2, CH 4 and/or N 2 under very mild conditions (<120 °C) and with accurate selectivity toward different reaction products (up to 95%). In this Perspective, we stablish the fundamentals of permanently polarized materials, providing the generalized concepts of the permanent polarized state and some representative examples of applying the TSP approach to a wide variety of materials. More specifically, we provide empirical evidence of the polarized state after applying the TSP treatment to quartz nanopowder, binary metal oxides (TiO 2 and ZrO 2 ) and different synthetic polymers, confirming the obtaining of enhanced electrical properties and the associated structural changes. Finally, the implications, challenges and perspectives of the polarized state are discussed considering different fields, such as catalysis, biomedicine, optics and electronics, sensors and energy storage devices.