Low temperature sintering of iron-barium co-doping bismuth sodium titanate lead free piezoelectric

This work reports a detailed study of the crystal structure and electrical properties of a potential lead-free piezoelectric Bi0.5Na0.5TiO3 co-doped with Ba2+ and Fe3+ sintered at relatively low temperature (900 °C). The effect that co-dopants have over the electric properties in (Bi0.5Na0.5)1-xBaxTi1-yFeyO3-0.5y, varying x from 0 to 0.075, x=0.025, and y from 0 to 0.075, y=0.025, was evaluated. XRD analysis showed a successful synthesis of co-doped BNT ceramics with a rhombohedral structure for samples with x < 0.075. In contrast, the sample with x = 0.075 exhibited the coexistence of the rhombohedral and tetragonal structures, confirmed by Rietveld refinement. The co-doping promotes the grain size growth and increase the pellets’ density from 93% to 98%. Dielectric spectroscopy analysis, conducted in the range from 25 to 500 °C, showed an increase in the relative permittivity with the dopant concentration, specifically at high temperatures. Electric analysis validate the piezoelectric behavior and the electric polarization of the co-doped BNT ceramics, unveiling a maximum remnant polarization (Pr) of 25.6 µC/cm2 and, a maximum piezoelectricity coefficient of 53 pC/N, which varied depending on the composition. The obtained results demonstrate that co-doping BNT ceramics with Ba2+ and Fe3+ cations lower the sintering temperature typically used in the solid-state reaction to obtain pure BNT, showing similar properties compared to those of the same material sintered at higher temperatures and longer times.本研究针对在相对低温（900℃）下烧结的、经Ba²+与Fe³+共掺杂的潜在无铅压电材料钛酸铋钠（Bi₀.₅Na₀.₅TiO3，简称BNT）的晶体结构与电学性能展开了详细研究。本研究评估了共掺杂剂对(Bi₀.₅Na₀.₅)₁₋ₓBaₓTi₁₋ᵧFeᵧO₃₋0.5ᵧ体系电学性能的影响，其中x取值范围为0至0.075，步长Δx=0.025，y取值范围为0至0.075，步长Δy=0.025。X射线衍射（X-ray Diffraction，XRD）分析结果显示，当x<0.075时，成功合成了具有菱方结构的共掺杂BNT陶瓷。与之相反，当x=0.075时，样品呈现菱方与四方结构共存的特征，该结果通过里特维尔德（Rietveld）精修得到验证。共掺杂可促进晶粒生长，并将陶瓷坯体的致密度从93%提升至98%。在25℃至500℃范围内开展的介电频谱分析结果表明，随着掺杂剂浓度提升，材料的相对介电常数呈上升趋势，该现象在高温区间尤为显著。电学性能分析验证了共掺杂BNT陶瓷的压电行为与电极化特性，结果显示其最大剩余极化强度（remnant polarization, Pr）可达25.6 µC/cm²，最大压电系数为53 pC/N，二者均随组分变化而改变。本研究所得结果证实，采用Ba²+与Fe³+阳离子共掺杂BNT陶瓷，可降低固相反应法制备纯相BNT陶瓷通常所需的烧结温度，且所得材料的性能与在更高温度、更长保温时间下烧结的纯相BNT陶瓷相当。