Electrical properties, defect chemistry and local lattice relaxation in Nb2O5 modified 0.94(Na0.5Bi0.5)TiO3-0.06BaTiO3 ferroelectrics

Single crystals of x at.% Nb + 0.94(Na0.5Bi0.5)TiO3-0.06BaTiO3 (x%-Nb:NBT-6BT, x = 0.12, 0.23, and 0.48) show improved ferroelectric and piezoelectric properties. In particular, the large piezoelectric constant (d33 = 532 pC/N) and high field-induced strains (Smax = 0.57%) in 0.23%-Nb:NBT-6BT single crystal demonstrate its promising application potential. The underlying mechanisms were investigated directively by atomistic scale simulations. We found that, Nb5+ cations prefer to substitute Ti4+ cations on B-site and will first fill up the oxygen vacancies generated due to the loss of Bi2O3 and/or Na2O. Higher concentration of Nb2O5, however, will be compensated by Ti and/or Bi vacancies. The ions positions surrounding the defect center(s) were identified.