Origin of high mechanical quality factor in CuO-doped (K, Na)NbO₃-based ceramics

Abstract

The origin of a high mechanical quality in CuO-doped (K, Na)NbO₃-based ceramics is addressed by considering the correlations between the lattice positions of Cu ions and the hardening effect in K_0.48Na_0.52+xNbO₃--0.01CuO ceramics. The Cu ions simultaneously occupy K/Na and Nb sites of these ceramics with x = 0 and 0.02, only occupy the K/Na site of the ceramics with x = --0.02, and mostly form a secondary phase of the ceramics with x = --0.05. The Cu ions lead to the hardening of ceramics with an increase of E_C and Q_m by only occupying the K/Na site, together with the formation of double hysteresis loops in un-poled compositions. A defect model is proposed to illuminate the origin of a high Q_m value, that is, the domain stabilization is dominated by the content of relatively mobile O^2-- ions in the ceramics, which has a weak bonding with Cu_K/Na defects.

Keywords

lead-free piezoelectric ceramic / (K, Na)NbO₃ (KNN) / mechanism of hardening effect / mechanical quality factor Q_m / domain stabilization

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Acknowledgements

This work was supported by the National Natural Science Foundation of China (NSFC; Grant Nos. 11305152, 51272164, 50772068 and 50972095) and Foundation of Doctor Training Program in University and College in China (Grant Nos. 20030610035 and 20080610020).

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