Screen Printed Copper and Tantalum Modified Potassium Sodium Niobate Thick Films on Platinized Alumina Substrates

We show how sintering in different atmospheres affects the structural, microstructural, and functional properties of ~30 mu m 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 degrees 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 mu m to ~2 mu m, 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 d(33) coefficient of 64 pm/V and an effective thickness coupling coefficient k(t) 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.

Automated summary

This study investigates the impact of sintering in different atmospheres on the properties of KNN thin films, highlighting the benefits of using packing powder for achieving phase-pure films. Thick films sintered in oxygen exhibit promising piezoelectric properties and low mechanical losses, making them potential candidates for lead-free piezoelectric energy harvesting applications.