Experimental evidence of breakdown strength and its effect on energy-storage performance in normal and relaxor ferroelectric films

Normal-ferroelectric Pb(Zr_0.52Ti_0.48)O₃ (PZT) and relaxor-ferroelectric Pb_0.9La_0.1(Zr_0.52Ti_0.48)O₃ (PLZT) thin-films are deposited on SrRuO₃-covered SrTiO₃/Si substrates. An ultrahigh recoverable energy-storage density (U_reco) of 68.2 J/cm³ and energy efficiency (η) of 80.4% are achieved in the PLZT thin-films under a large breakdown strength (E_BD) of 3600 kV/cm. These values are much lower in the PZT thin-films (U_reco of 10.3 J/cm³ and η of 62.4% at E_BD of 1000 kV/cm). In addition, the remanent polarization (P_r) and dielectric-constant are also investigated to evaluate the breakdown strength in thin-films. Polar nano-regions (PNRs) are created in the PLZT thin-films to enable relaxor behavior and lead to slim polarization loops along with very small P_r. The excellent operating temperature of energy-storage performance and also the breakdown strength obtained in the PLZT thin-films are mainly ascribed to the presence of PNRs. Moreover, both PZT and PLZT thin-films exhibit superior performance up to 10¹⁰ times of charge-discharge cycling.