Effect of lattice occupation behavior of Li+ cations on microstructure and electrical properties of (Bi1/2Na1/2)TiO3-based lead-free piezoceramics

The multisite occupation of Li+ cations in perovskite structure of (Bi1/2Na1/2)TiO3-based solid solution is investigated, which is rarely reported in previous studies. The multisite occupation in relation to the Li2CO3 doping level has been demonstrated with the aid of the microstructure and temperature-dependent conductivity analysis: As the addition of Li2CO3 is below 0.75 mol. %, the introduced Li+ cations precede to enter the A sites of the perovskite lattice to compensate for the A-site deficiency stemming from the high-temperature sintering process. Once the addition exceeds 0.75 mol. %, the excess Li+ cations will occupy B sites to substitute for Ti4+ and give rise to the generation of oxygen vacancies. The proposed multisite occupation behavior of Li+ cations and its derivative effects, involving the clamping effect or grain size effect, have made the piezo-/ferroelectric performances of the 0.85BNT–0.10BKT–0.05BT ceramics optimized at the Li2CO3 addition of 1.0 mol.%:d33 = 163 pC/N, Pr = 40.9 μC/cm2.