$\left(\mathrm{N}{\mathrm{a}}_{1/2}\mathrm{B}{\mathrm{i}}_{1/2}\right)\mathrm{Ti}{\mathrm{O}}_3\text{−}x\mathrm{BaTi}{\mathrm{O}}_3\left(\mathrm{NBT}\text{−}x\mathrm{BT}\right)$ single crystal, as one of the most promising candidates to replace lead-based ferroelectrics, is a typical and unique lead-free system with morphotropic phase boundary (MPB) by far. In this paper, the phase transition process of NBT-0.06BT crystal in a wide temperature range of $20\sim 550{}^{\circ }\mathrm{C}$ was analyzed at atomic scale by theoretical fitting to the measured synchrotron radiation x-ray absorption fine structure spectra quantitatively. Detailed analysis revealed a gradually transition of local structure at the point of phase transition from rhombohedral to tetragonal phase in NBT-0.06BT crystal on the bond lengths of Bi-O and Bi-Ti. The continuous evolution of local structure with no obvious barrier to overcome is one of the intrinsic characteristics of MPB at atomic scale and is responsible for the high piezoelectric properties. These results could promote the understanding of the origin of the high piezoelectric performance around the MPB and meanwhile guide new lead-free material designs.

中文翻译：

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同步加速器X射线吸收精细结构光谱研究（Na1 / 2Bi1 / 2）TiO3-0.06BaTiO3无铅单晶中的相变局部结构证据

$（\mathrm{ñ}{\mathrm{一种}}_{\mathrm{1个}/2}\mathrm{乙}{\mathrm{一世}}_{\mathrm{1个}/2}）钛{\mathrm{Ø}}_3\text{-}X\mathrm{钡钛}{\mathrm{Ø}}_3（\mathrm{NBT}\text{-}X\mathrm{英国电信}）$作为替代铅基铁电体的最有希望的候选材料之一，单晶是一种典型且独特的无铅系统，目前为止具有形态相边界（MPB）。本文研究了NBT-0.06BT晶体在宽温度范围内的相变过程$20〜550{}^{\circ }\mathrm{C}$通过理论拟合来定量分析所测量的同步辐射X射线吸收精细结构光谱，从而在原子尺度上进行分析。详细的分析显示，在Bi-O和Bi-Ti的键长上，NBT-0.06BT晶体中从菱面体到四方相的相变点，局部结构逐渐过渡。局部结构的连续演变没有明显的障碍可以克服，这是MPB在原子尺度上的固有特征之一，并具有高压电性能。这些结果可以促进对MPB周围高压电性能起源的理解，同时指导新的无铅材料设计。