Effect of different MnO2 phases (β-, γ-, and ε-) on the microstructure and piezoelectric properties of Pb(Zr1/2Ti1/2)O3–Pb(Zn1/3Nb2/3)O3–Pb(Ni1/3Nb2/3)O3 ceramics for energy harvesting

This study reports 0.83Pb(Zr1/2Ti1/2)O3–0.11Pb(Zn1/3Nb2/3)O3–0.06Pb(Ni1/3Nb2/3)O3 (PZNNT) ceramics doped with MnO2 were obtained through the conventional solid-state reaction method. The effects of MnO2 additive with different phases (β-, γ-, and ε-) on the microstructure and piezoelectric properties of PZNNT ceramics were discussed under the same condition. On the basis of X-ray photoelectron spectroscopy (XPS), the results clearly showed that Mn ions in different crystal forms of MnO2 could convert from Mn4+ ions to diverse valence states (Mn2+, Mn3+) and produce different oxygen vacancies. Furthermore, the relevant electric properties of samples increased as follows: PZNNT/β-MnO2 < PZNNT/ε-MnO2 < PZNNT/γ-MnO2. The optimal electric properties could be obtained by adding 1.5 mol% γ-MnO2, the energy conversion factor (d33 × g33), the mechanical quality factor (Qm), the electromechanical coupling factor (kp), and the Curie temperature (Tc) which were 9859 × 10−15 m2/N, 357, 0.556, and 315 °C, respectively. It indicates that γ-MnO2-modified PZNNT ceramics are potential candidate materials for piezoelectric energy harvesting.