Study of Nanoporous Anodic Aluminum Oxide as a Template Filled with Piezoelectric Materials

This paper is devoted to method of nanostructuring of piezoelectric potassium niobate (KNbO3) material in order to improve its voltage generating ability for potential application as energy harvesting. The main goal is geometrical structuring of the piezoelectric material to obtain higher piezoelectric voltage per unit volume in comparison with thin non-structured film from the same material. This is possible due to template properties of porous anodic aluminum oxide (AAO). It was found that KNbO3 grown by sputtering in the nanopores of AAO generates an effective piezoelectric voltage of 410 mV from volume of 0.001 cm3 at mass load of 40 g and frequency of 50 Hz. For comparison, non-structured films with thickness lower than 200 nm and area resulting in a volume of 0.00006 cm3 the generated voltage was 1.78 mV, which means that this type of nanostructuring leading to two orders of magnitude increase of the surface-to-volume ration enhances the piezoelectric response 2.3 times.