Electromechanical and ferroelectric properties of (Bi1∕2Na1∕2)TiO3–(Bi1∕2K1∕2)TiO3–BaTiO3 lead-free piezoelectric ceramics

TLDR

Lead‑free piezoelectric ceramics of the (0.95−x)(Bi₁/₂Na₁/₂)TiO₃–x(Bi₁/₂K₁/₂)TiO₃–0.05BaTiO₃ system have been investigated. The study examined how varying the BKT content influences the electrical properties and crystal structure. BNT–BKT–BT5 ceramics show superior piezoelectric performance (d₃₃ = 148 pC N⁻¹, kₚ = 34 %, kₜ = 49.2 %, ε₃₃ᵀ/ε₀ = 700, tan δ = 2 % at 1 kHz), higher remanent polarization, lower coercive field than 0.95BNT–0.05BT, and X‑ray diffraction confirms BKT incorporation forms a solid solution that transforms the crystal symmetry from rhombohedral to tetragonal at higher BKT content.

Abstract

Lead-free piezoelectric ceramics (0.95−x)(Bi1∕2Na1∕2)TiO3–x(Bi1∕2K1∕2)TiO3–0.05BaTiO3 (abbreviated as BNT–BKT–BT100x, with x ranged from 0 to 20mol%) have been studied. Effects of amount of BKT on the electrical properties and crystal structure were examined. BNT–BKT–BT5 ceramics give good performances with piezoelectric constant d33=148pC∕N, electromechanical coupling factor kp=34%, kt=49.2%, free permittivity ε33T∕ε0=700, and dissipation factor tanδ=2% at 1kHz. Accordingly, the sample shows larger remanent polarization and lower coercive field than 0.95BNT–0.05BT ceramics. X-ray diffraction analysis shows that incorporated BKT diffuses into the BNT–BT lattice to form a solid solution during sintering, but changes the crystal structure from rhombohedral to tetragonal symmetry at higher BKT amounts.