Large strain response in acceptor- and donor-doped Bi0.5Na0.5TiO3-based lead-free ceramics

Effects of Fe and La addition on the dielectric, ferroelectric, and piezoelectric properties of Bi0.5Na0.5 TiO3-Bi0.5Li0.5TiO3-BaTiO3-Mn ceramics were investigated. Similar to the doping effect in lead-based piezoelectric materials, here the Fe-doped ceramic created a hard effect with an improved mechanical quality factor (Q(m)) similar to 160, coercive field (E-c) similar to 2.9 kV/mm, decreased dielectric constant (epsilon(T)(33)/epsilon(0)) similar to 803; and loss (tan delta) similar to 0.024 while the La-doped one indicated a soft feature with improved piezoelectric constant (d(33)) similar to 184 pC/N, epsilon(T)(33)/epsilon(0) similar to 983; tan delta similar to 0.033, and decreased E-c similar to 2.46 kV/mm. In addition, the temperature dependence of the ferroelectric hysteresis loops and strain response under unipolar electric field was also studied. Around the depolarization temperature T-d, large strain value was obtained with the normalized d(33)* up to similar to 1,000 pC/N, which was suggested originated from the development of the short-range order or non-polar phases in the ferroelectric matrix. All these would provide a new way to realize high piezoelectric response for practical application in different temperature scale.