Ga₂O₃ doping and vacancy effect in KNN--LT lead-free piezoceramics

Abstract

Ga₂O₃ was doped into 0.95(K_0.48Na_0.52)NbO₃–0.05LiTaO₃ (KNN–LT) ceramics and its influences on the sintering behavior, phase structure and electrical properties of ceramics were studied. Firstly, SEM observation exhibits that more and more glass phase appears in ceramics with the gradual addition of Ga₂O₃, which determines the continuous decrease in sintering temperatures. And the addition of Ga₂O₃ is also found to increase the orthorhombic–tetragonal transition temperature (T_O–T) of system to a higher level. Secondly, both the density and the coercive field (E_C) of ceramics increase firstly and then decrease with increasing the Ga₂O₃ content, and the KNN–LT–xGa sample at x = 0.004 shows a pinched P–E hysteresis loop. Finally, the impedance characteristics of KNN–LT–xGa ceramics were investigated at different temperatures, revealing a typical vacancy related conduction mechanism. This work demonstrates that Ga₂O₃ is a good sintering aid for KNN-based ceramics, and the vacancy plays an important role in the sintering and electrical behaviors of ceramics.

Keywords

lead-free piezoceramics / Ga ₂O ₃ / phase structure / piezoelectric properties / sintering behavior

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