Large strain response in acceptor- and donor-doped Bi_(0.5)Na _(0.5)TiO_3-based lead-free ceramics

摘要

Effects of Fe and La addition on the dielectric, ferroelectric, and piezoelectric properties of Bi_(0.5)Na_(0.5)TiO _3-Bi_(0.5)Li_(0.5)TiO_3-BaTiO _3-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) ~ 160, coercive field (E _c) ~ 2.9 kV/mm, decreased dielectric constant (ε_(33){~(T/ε)_0)～ 803, and loss (tanδ) ~ 0.024 while the La-doped one indicated a soft feature with improved piezoelectric constant (d _(33)) ~ 184 pC/N, ε_(33)~(T/ε)_0 ～ 983, tanδ ~ 0.033, and decreased E _c ~ 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 ~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.