Effects of ZnO nanoneedles addition on the mechanical and piezoelectric properties of hard PZT-based composites

Hard PZT (PZT4)-based composites embedded by ZnO nanoneedles (denoted as PZT/ZnO_n) were fabricated by a solid state sintering technique. The characteristic diffraction peaks of the perovskite PZT and ZnO phases were identified from the studied composites, indicating the retention of ZnO _n. With increasing ZnO_n content, the grain size of the composites was reduced gradually. In contrast with the pure PZT, the PZT/ZnO_n composites possessed more excellent mechanical properties, while the piezoelectric properties were reduced by a certain extent. The best mechanical properties of PZT/ZnO_n composites were obtained by sintering at 1,150 °C with 1.5 wt% ZnO nanoneedles addition: fracture toughness K_IC ∼ 2.04 MPa m^1/2, flexural strength σ_f ∼ 105.44 MPa, compressive strength σ_c ∼ 543.89 MPa. The piezoelectric properties of the PZT/ZnO_n composites were found to be lower than that of the pure PZT with dielectric permittivity ε_r of 768-893, piezoelectric coefficient d ₃₃ of 240-260pC/N, mechanical quality factor Q_m of 340-650 and planar electromechanical coupling k_p of 0.5-0.55.