Emerging new phase boundary in potassium sodium-niobate based ceramics

Abstract

A review of the newly emerging “new phase boundary” in potassium sodium niobate-based ceramics with high performance.

Reduced degree of phase coexistence in KNN-Based ceramics by competing additives

“…In addition, the atomic percentage also demonstrates the increased content of Ba element ( Figures 6(a3, b3, c3)). As is well known, electrical properties will be enhanced in the multi-phase coexistence region [1,5].…”

“…Actually, this work not only compares the controlling ability of Ba2+ and (Bi0.5Ag0.5)2+ to TO-T but also significantly reveals which and how elements cause the reduced TO-T, further promoting the understanding of the role of additives on the phase structure. Particularly, previous investigations only revealed the role empirically from ɛr-T curves without further analyzing the underlying physical origin [1,2]. However, there is still a long way to completely understand the effects of additives on the phase structure of KNN-based ceramics, which needs more efforts in the future.…”

“…Driven by the increasing demand for sustainable development, environmentally friendly lead-free piezoceramics are developed to hopefully replace the lead-based counterparts [1][2][3][4][5]. Particularly, the milestone reported by Saito et al accelerated the development of potassium sodium niobate {(K, Na)NbO3, KNN} based ceramics due to the promising piezoelectricity and temperature stability [6].…”

“…Inspired by this, Wu et al proposed a new way to construct the multi-phase coexistence by simultaneously adjusting TO-T and rhombohedral-orthorhombic phase transition temperature (TR-O) to the room temperature after ten years, resulting in the continuous increase in piezoelectric coefficient d33 [1,[7][8][9][10][11][12]. Currently, d33 values of state-of-the-art non-textured KNN-based ceramics are as high as 400-650 pC/N, comparable to those of commercial soft PZT-based ceramics [1,7,11,12].…”

“…Thus, the current consideration or choice for additives still remains in the exploratory stage, which hinders the further development of KNN-based ceramics. When surveying the reported additives, ion substitutions (e.g., Li+, Ag+, Sb5+, and Ta5+) and/or ABO3-type additives were found to effectively construct the phase boundary and obtain high d33 values [1,2,13]. Particularly, A2+B4+O3-type additives, represented by (Bi0.5M0.5)NO3 (M=Na/Ag/K, N=Zr/Hf), were widely utilized 3 to reduce TO-T [14][15][16].…”