Highly accelerated lifetime testing of potassium sodium niobate thin films

Highly accelerated lifetime tests of 2 and 3 μm thick potassium sodium niobate [(K_0.5, Na_0.5)NbO₃, KNN] films with different thicknesses were measured under electric fields ranging from 160 to 350 kV/cm and temperatures ranging from 90 to 210 °C. The medium time to failure (t₅₀) was determined from a lognormal distribution plot of failure times of up to 22 electrodes per measurement condition. The activation energy (E_a) for failure was 0.74 ± 0.04 eV and 0.92 ± 0.05 eV for the 2 μm and 3 μm KNN films, respectively. The voltage acceleration factor was 3.5 ± 0.34 for the 3 μm film. But the electric field dependence of t₅₀ for the 2 μm film showed two regions with similar N, 6.67 and 6.94 ± 0.23, respectively. Energy-dispersive X-ray spectroscopy was employed to investigate the Na⁺ and K⁺ ion distributions in KNN films.