Author:

Keywords:

Science & Technology, Physical Sciences, Technology, Chemistry, Physical, Materials Science, Multidisciplinary, Metallurgy & Metallurgical Engineering, Physics, Applied, Physics, Condensed Matter, Chemistry, Materials Science, Physics, lead-free, KNN, thick film, microstructure, electromechanical properties, MECHANICAL QUALITY FACTOR, PIEZOELECTRIC PROPERTIES, ELECTRICAL-PROPERTIES, CERAMICS, PZT, K0.5NA0.5NBO3, STRONTIUM, PRESSURE, 03 Chemical Sciences, 09 Engineering, 34 Chemical sciences, 40 Engineering

Abstract:

We show how sintering in different atmospheres affects the structural, microstructural, and functional properties of ~30 μm thick films of K0.5Na0.5NbO3 (KNN) modified with 0.38 mol% K5.4Cu1.3Ta10O29 and 1 mol% CuO. The films were screen printed on platinized alumina substrates and sintered at 1100 °C in oxygen or in air with or without the packing powder (PP). The films have a preferential crystallographic orientation of the monoclinic perovskite phase in the [100] and [-101] directions. Sintering in the presence of PP contributes to obtaining phase-pure films, which is not the case for the films sintered without any PP notwithstanding the sintering atmosphere. The latter group is characterized by a slightly finer grain size, from 0.1 μm to ~2 μm, and lower porosity, ~6% compared with ~13%. Using piezoresponse force microscopy (PFM) and electron backscatter diffraction (EBSD) analysis of oxygen-sintered films, we found that the perovskite grains are composed of multiple domains which are preferentially oriented. Thick films sintered in oxygen exhibit a piezoelectric d33 coefficient of 64 pm/V and an effective thickness coupling coefficient kt of 43%, as well as very low mechanical losses of less than 0.5%, making them promising candidates for lead-free piezoelectric energy harvesting applications.