Degradation of KNN-Based Lead-Free Piezoelectric Material Under Gamma Irradiation

(Na
_0.5
K
_0.5
)NbO
₃
-(Bi
_0.5
Li
_0.5
)TiO
₃
-BaZrO
₃
lead-free piezoelectric ceramics are irradiated to 50 Mrad(Si) by Co-60 gamma rays. The degradation behaviors of piezoelectric and ferroelectric characteristics are investigated. Most characteristics degrade fast during the first 10-Mrad(Si) irradiation and then degrade slowly. The 30% degradation of material performance at about 15 Mrad(Si) has been observed, which is much worse than that of lead zirconate titanate [Pb(Zr
₅₂
Ti
₄₈
)O
₃
, PZT] ceramics. The (K, Na)NbO
₃
-based ceramics have much more complex microstructures and interfaces than PZT ceramics, leading to the existence of much more defects and neutral traps. During irradiation, more ionized carriers are trapped. Stronger built-in electric field is established by inducing faster degradation of the material performance. The saturation of trapped charges at the domain wall might be the cause of the slowly degradation curve. Therefore, to successfully replace the lead-based piezoelectric material and improve the radiation tolerance in extreme radiation environment, the appropriate material compositions and corresponding fabrication process need to be considered.