Modification And Properties Of Pb(Mn (1/3)Sb₂/3)O₃-Pb(Zr,Ti)O₃ Based High Power Piezoelectric Ceramics

As the core elements in ultrasonic motors (USM) that transfer electric energy to mechanical energy, the performance of piezoelectric materials is crucial to USMs. PMnS [Pb(Mn_1/3Sb_2/3)O₃]-PZT based ceramics possess high electromechanical coupling coefficients and mechanical quality factors, and can vibrate in a high velocity under high power, which makes them suitable for applications in USMs. Based on PMnS-PZT, two quaternary systems, PZN [Pb(Zn_1/3Nb_2/3)O₃]-PMnS-PZT and PMgT [Pb(Mg_1/3Ta_2/3)O₃]-PMnS-PZT were studied in this thesis work.Sm2O3 and Ta2O5 were adopted to dope low temperature sintered PZN-PMnS-PZT ceramics in A-sites and B-sites, respectively. Both of them do not deteriorate the low temperature sintering behavior of the ceramics and to different degrees, they improve the densification and uniformity of the microstructure, which therefore increases Qm. Excessive Sm2O3 doping can cause Sm aggregation at grain boundaries and promote the amount of pyrochlore, worsening the soft properties. By contrast, Ta doping induces an unnoticeable change in the structure and electric properties of the ceramics. The ceramics doped with 0.25 wt% Sm2O3 and 0.75 wt%Ta2O5 show good performance: d₃₃ = 315 pC/N, Q_m = 1012, k_p = 0.55, tanδ= 0.44% and d₃₃ = 308 pC/N, Q_m = 1055, k_p = 0.57, tanδ= 0.3%, respectively.A new type of quaternary ceramics, xPMgT-(0.1-x)PMnS-0.9PZT (0≤x≤0.1), were fabricated by incorporating relaxor Pb(Mg_1/3Ta_2/3)O₃. With the increase of PMgT, the tetragonality c/a ratios increase, and the grains are coarsened gradually. The ferroelectric analysis reveals that Mn ions are fundamental in producing oxygen vacancies. The internal dipole field formed by oxygen vacancies and aliovalent cations can suppress the domain switching significantly. The ceramics become soft after PMnS is completely replaced. As for the electric properties, both d33 and kp present a constantly increasing trend, while Qm reaches its maximum at x = 0.05 due to its strongest dipole field. 0.05PMgT-0.05PMnS-0.9PZT shows the best overall performance:ε₃₃^T= 683, tanδ= 0.3%, d₃₃ = 227 pC/N, k_p = 0.55, Q_m = 1830.The vibrating velocities of PMgT-PMnS-PZT ceramics were measured using a laser Doppler vibrometer. It shows that 0.05PMgT-0.05PMnS-0.9PZT can reach a high velocity of 900 mm/s.