Achieving Both Giant d₃₃ and High T_C in Patassium-Sodium Niobate Ternary System

Both giant d33 and high TC have been obtained in a lead-free piezoelectric ternary system (0.995 - x)K0.48Na0.52NbO3-0.005BiScO3-xBi0.5(Na0.7K0.2Li0.1)0.5ZrO3. Thanks to the rhombohedral-tetragonal phase coexistence and the enhanced dielectric and ferroelectric properties, the ceramic with a composition of x = 0.04 shows a giant d33 of ∼366 pC/N together with TC of ∼335 °C, thereby paving the way for achieving both high d33 and high TC in KNN-based materials. In addition, such a ceramic has a good thermal stability of d33 (e.g., d33 > 319 pC/N, T ≤ 300 °C) and an enhanced stability of ferroelectric properties against temperature. The domain-wall energy barrier of ∼0.15 eV is derived from the temperature dependence of the back-switching polarization.