Electrical properties of manganese modified sodium potassium lithium niobate lead-free piezoelectric ceramics

Effects of MnO2 doping on the microstructure, densification, dielectric, ferroelectric and piezoelectric properties of (Na0.5K0.5)(0.935)Li0.065NbO3 (NKLN) lead-free piezoelectric ceramics were investigated. On the one hand, the addition of a small amount of MnO2 has little effect on the crystalline structure, however, slightly promotes sintering and grain growth, and improves the uniformity of microstructure to a certain degree. On the other hand, MnO2 doped NKLN ceramics show hard properties in piezoelectric activities, possessing decreased room-temperature dielectric constant, loss tangent and piezoelectric constants d (33), and increased mechanical quality factors Q (m). The 1.2 mol% MnO2 doped NKLN ceramics have a loss tangent of approximately 1%, a Q (m) of 170 and a d (33) of 150 pC/N. These effects were considered to come from the formation of oxygen vacancies and the multi-valence states of Mn ions.