Stoichiometric and non-stoichiometric Mn modification on high-power properties in PYN-PZT piezoelectric ceramics

The types of dopants lead to distinctive microstructural evolution behavior and physical properties in materials. In this study, the effect of stoichiometric and non-stoichiometric Mn modification, namely Pb(Mn_1/3Nb_2/3)O₃ (PMnN) and MnO₂, on the microstructure and properties of Pb(Yb_1/2Nb_1/2)O₃-PbZrO₃-PbTiO₃ (PYN-PZT) piezoelectric ceramics are systematically investigated. It was found that stoichiometric PMnN modification inhibits the grain growth while non-stoichiometric MnO₂ modification promotes it, and thus the former yields stronger high-power characteristics (higher internal bias field E_i and larger mechanical quality factor Q_m) than the latter. Specifically, with an equivalent amount of Mn modification (2 mol%), PMnN and MnO₂ modification PYN-PZT ceramics exhibit significantly different values for average grain size (1.21 μm vs. 14.12 μm), E_i (8.5 kV/cm vs. 5 kV/cm), and Q_m (2376 vs.1134). To further evaluate high-power performance, the vibration velocity v of these two modified PYN-PZT under high driving conditions was measured. Under an AC electric field of 3.5 V/mm, the PYN-PZT+6PMnN ceramics exhibit a v of up to 0.95 m s⁻¹, larger than both MnO₂-doped PYN-PZT (0.72 m s⁻¹) and unmodified PYN-PZT ceramics (0.1 m s⁻¹), and far outperformance than both PZT-4 and PZT-8 ceramics. Furthermore, to elucidate the origin of the exceptional high-power performance of PMnN-modified PYN-PZT, we performed phase-field simulations revealing a pinning effect of the grain boundary on domain wall motion. Consequently, the small grain size (high grain boundary density) in PMnN-modified PYN-PZT exhibits a strong pinning effect, resulting in a large Q_m and outstanding high-power performance.