The mechanism for the enhanced piezoelectricity in multi-elements doped (K,Na)NbO3 ceramics

Xiaoyi Gao,Shujun Zhang,Lianmeng Zhang,Zibin Chen,Zhenxiang Cheng,Wen Chen,Bei Li,Qiang Shen,Qi Guo ,Hua Hao,Xiaozhou Liao,Xu Zhang,Qinfen Gu,Jinsong Wu,Xiangyu Meng,Hanxing Liu,Huajun Sun,Simon P Ringer,Fĕi Li ,Jianli Wang,Yao Liu

doi:10.1038/s41467-021-21202-7

Abstract

(K,Na)NbO3 based ceramics are considered to be one of the most promising lead-free ferroelectrics replacing Pb(Zr,Ti)O3. Despite extensive studies over the last two decades, the mechanism for the enhanced piezoelectricity in multi-elements doped (K,Na)NbO3 ceramics has not been fully understood. Here, we combine temperature-dependent synchrotron x-ray diffraction and property measurements, atomic-scale scanning transmission electron microscopy, and first-principle and phase-field calculations to establish the dopant–structure–property relationship for multi-elements doped (K,Na)NbO3 ceramics. Our results indicate that the dopants induced tetragonal phase and the accompanying high-density nanoscale heterostructures with low-angle polar vectors are responsible for the high dielectric and piezoelectric properties. This work explains the mechanism of the high piezoelectricity recently achieved in (K,Na)NbO3 ceramics and provides guidance for the design of high-performance ferroelectric ceramics, which is expected to benefit numerous functional materials.

Highlights

(K,Na)NbO3 based ceramics are considered to be one of the most promising lead-free ferroelectrics replacing Pb(Zr,Ti)O3
The enhanced piezoelectric activity in KNN ceramics has been attributed to the polymorphic phase transition (PPT) shifting downward to room temperature, achieved by doping various elements, such as Li+, Sb5+, Ta5+, etc[6,7,8,9,10,11,12]
The major properties and field-emission scanning electron microscopic (FE-SEM) images of the KNN-Bi,Sb,Zr sample are given in Supplementary Table 1 and Supplementary Fig. 1 respectively, which are compared with those of the single element doped KNNs

Summary

Introduction

(K,Na)NbO3 based ceramics are considered to be one of the most promising lead-free ferroelectrics replacing Pb(Zr,Ti)O3. Among the known piezoelectric materials, perovskite ferroelectric materials, such as Pb(Zr,Ti)O3 (PZT) and relaxorPbTiO3 based solid solutions, have exhibited the highest piezoelectric coefficient and electromechanical coupling factors due to the existence of morphotropic phase boundary (MPB) and the ability to tailor properties between “soft” and “hard” piezoelectric responses[1,2,3,4]. As a result, they have been the mainstay piezoelectric materials and have occupied the largest share of the piezoelectric ceramics market. We demonstrate the connections between composition fluctuation, microstructure heterogeneity and macroscopic properties, and provide inspiration for the design of lead-free ferroelectrics with high piezoelectricity and thermal stability

Methods

Results

Conclusion