Film densification and electrotransportation of alkali ions in solution-deposited piezoceramic thin films under electric stress

We have studied the impact of electric-field assisted densification of a low temperature solution-processed piezoelectric inorganic film (potassium sodium niobate, KNN). A concentrated (KxNa1-x(NbO3), x=0.5) sol of the material was drop casted on an insulating SiO2 substrate with two electrodes deposited in a lateral diode geometry. Surface metrology and compositional scans on the post-processed film revealed a cracked morphology with apparent densification and a stoichiometric shift from 51:49 to 31:69 (K:Na). An image processing method was used on electron microscopy images to estimate a similar to 20% volume reduction over an area of 400 mu m(2) using film topographical data. Further, the system was simulated using a finite element method on a 3D model system, and the simulated electric field lines appear to explain the observed post-annealed densified profiles.

Automated summary

In this study, we investigated the impact of electric-field assisted densification on a low temperature solution processed piezoelectric inorganic film (KNN). The experimental results showed cracked morphology and densification in the post-processed film, along with a shift in the stoichiometric ratio. Using image processing and finite element simulation, we further confirmed these observations.