Leakage and relaxation phenomena have a significant effect on electrical properties of structures based on thin ferroelectric films [1]. One of the key sources of low-frequency relaxation phenomena is the defects chemistry in PZT caused by volatility of PbO and formation of oxygen and lead vacancies. The migration of oxygen vacancies is the most responsible for leakage current, electrical degradation, fatigue, retention, imprint, and other electrical characteristics of PZT ceramic films.
In this report, we discuss the comparative quantitative studies of relaxation processes in PZT capacitors with different electrode materials having opposite behavior with respect to the oxygen vacancies migration. The PZT/Au and PZT/lanthanum nickelate (LNO) interfaces are «transparent» to the migration of oxygen vacancies, while the PZT/Pt or PZT/Ir interfaces are «impermeable» to oxygen vacancies, which leads to their excessive concentration at the interface when an applied electric field has corresponding polarity.
The capacitor structures were polarized before the short-circuit discharge measurements by a positive or negative voltage to provide saturation of spontaneous polarization (2.5–3 times higher than the coercive voltage). The low-frequency relaxation current was modeled by exponential functions with relaxation times τ1 and τ2. It is discovered that the permeability of the ferroelectric/electrode interfaces with respect to oxygen vacancies has a decisive influence on the low-frequency relaxation of PZT capacitors. The capacitors with «impermeable» to oxygen vacancies interfaces demonstrate 1.5 – 2 times lower relaxation charge and more than two times lower relaxation times τ1 and τ2 in contrast to ones with transparent interfaces. This is an important argument when choosing the design of a ferroelectric capacitor for various applications.
 
Acknowledgments
This work is supported by the RF Ministry of Science and Higher Education (? 0706-2023-0005).
 
 [1]     Podgorny, Y.V., Antonovich, A.N., Petrushin, A.A. et al. Effect of metal electrodes on the steady-state leakage current in PZT thin film capacitors. J Electroceram 49, 15–21 (2022).