Excellent thermal stability and enhanced piezoelectric performance of Bi(Ni2/3Nb1/3)O3‐modified BiFeO3–BaTiO3 ceramics

Abstract

AbstractLead‐free piezoelectric ceramics with excellent piezoelectric performance and temperature stability are vital to “stack up” against PZT in various applications. Thus, xBiFeO3‐(1‐x)BaTiO3(BF‐BT)‐based ceramics with high Curie temperatures have drawn increasing attention. However, BF‐BT based ceramics often show large leakage current due to the valence fluctuation of Fe ion. In this work, it is found that Bi(Ni2/3Nb1/3)O3 (BNN) can suppress the valence fluctuation of Fe ions effectively. The effects of BNN on the crystal structure, morphology, and electrical properties of 0.69BF‐0.31BT ceramics are investigated. For composition near morphotropic phase boundary of rhombohedral and tetragonal phases, the Curie temperature (Tc) is as high as 453°C, and the piezoelectric constant (d33), planar electromechanical coupling factor kp, and electric‐field‐induced strain ΔS can reach up to 191 pC/N, 31% and 0.236% (peak to peak), respectively. Moreover, these ceramics show excellent thermal stability. The d33 of 100 pC/N is still maintained at about 360°C and an ultrahigh strain (ΔS = 0.684%, peak to peak strain) is obtained at 190°C. Our work illustrates that the BF‐BT based ceramics can serve as potential candidates for sensor and actuator applications over a broad temperature range.