Structural disorder and oxygen octahedron evolution via defect engineering for properties enhancement in BF–BT ceramics

Abstract

The electrostrain properties of bismuth ferrite–barium titanate (BF–BT)‐based ceramics can be well regulated; however, this often occurs at the cost of piezoelectricity, and their electrostrain‐temperature stability is poor. To address these problems, defect engineering has been utilized to enhance the comprehensive properties via the unequal substitution of Na+. In this study, 0.69BiFeO3–0.3BaTiO3–0.01NaxNbO3 (BF–BT–NxN) (x = 0.8, 0.9, 1, 1.1, and 1.2) ceramics with different defect concentrations were prepared. Enhanced piezoelectricity and electrostrain (d33 = 165 pC/N and S = ∼0.22%, respectively) were obtained for the BF–BT–N0.9N ceramic. In particular, excellent temperature stability with a strain variation of only 12% from room temperature to 180°C was achieved. The introduction of NaxNbO3 reduced the degree of distortion of the oxygen octahedron, and the defects altered the local structure and heightened its disorder, leading to an enhancement in both the electrostrain and piezoelectric properties. In addition, the temperature‐dependent evolution of the oxygen octahedron structure was altered by defect engineering. A mutual compensation mechanism for the contribution of structural evolution and domain wall motion to electrostrain has been proposed to explain the excellent temperature stability.