Hardening behavior and highly enhanced mechanical quality factor in (K0.5Na0.5)NbO3-based ceramics

This paper relates the microstructure, crystallographic structure, ferroelectric, and piezoelectric properties of (K0.5Na0.5)NbO3 (KNN) ceramics modified with 0.38 mol% K5.4Cu1.3Ta10O29 (KCT) and different amounts of CuO. Results revealed that the addition of KCT and CuO were effective in enhancing the sinterability of KNN. The internal bias field (E-ib) increased from 0.3 kV/mm to 0.58 kV/mm at 0.5 mol% CuO-added KNN+KCT ceramics. The increase of E-ib, corresponds very well with the observed increase of the mechanical quality factor (Q(m)) from 112 to 2665 for 0.5 mol% CuO. Besides, addition of 0.5 mol% CuO to KNN+KCT resulted in a large increase of the EPR signal, which is related to the increased amount Cu2+ and a corresponding increase of the concentration of defect dipoles. This result is in good agreement with the increased E-ib and the resulting hardening behavior. (C) 2017 Elsevier Ltd. All rights reserved.