The complex interplay of local disorder with the structure and dynamics and their role in enhancing the electromechanical response makes relaxor ferroelectric materials fascinating both from the scientific and technological standpoints. It is generally believed that in chemically disordered ferroelectric solid solutions, the normal ferroelectric state gradually yields to a relaxor ground state on increasing the concentration of localized (point-defect-like) random-field centers. That a different kind of process can spontaneously stabilize a relaxor ground state is less known, especially in the family of ferroelectric perovskites. We demonstrate the occurrence of this less-known phenomenon in $(1-x){\mathrm{K}}_{0.5}{\mathrm{Bi}}_{0.5}\mathrm{Ti}{\mathrm{O}}_3\text{−}\left(x\right){\mathrm{Na}}_{0.5}{\mathrm{Bi}}_{0.5}\mathrm{Ti}{\mathrm{O}}_3[(1-x)\mathrm{KBT}-\left(x\right)\mathrm{NBT}]$. Unlike the gradual evolution common to most ferroelectric solid solutions, KBT-xNBT exhibits an abrupt crossover from a normal ferroelectric ground state to a full-blown relaxor ground state for $x>0.58$. We show that this abrupt crossover to the relaxor state is caused by stabilization of an incommensurate-like/highly disordered $M$-point ferroelastic distortion in the ergodic/paraelectric temperature regime. The abrupt crossover manifests as composition driven anomalous changes in several important properties such as dielectric response, electromechanical properties, tetragonality, and coercive field, electrostrain, and mimics a scenario often encountered in composition driven interferroelectric transformations.

中文翻译：

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在K0.5Bi0.5TiO3-Na0.5Bi0.5TiO3中由铁弹性不稳定性强迫的弛豫基态

局部无序与结构和动力学的复杂相互作用以及它们在增强机电响应中的作用使弛豫铁电材料从科学和技术的角度着迷。通常认为，在化学无序的铁电固溶体中，正常的铁电态随着增加局部（点缺陷）随机场中心的浓度而逐渐屈服为弛豫基态。很少有人知道另一种方法可以自发地稳定弛豫器的基态，尤其是在铁电钙钛矿中。我们展示了这种鲜为人知的现象的发生$（\mathrm{1个}-X）{\mathrm{ķ}}_{0.5}{双}_{0.5}钛{\mathrm{Ø}}_3\text{-}（X）{娜}_{0.5}{双}_{0.5}钛{\mathrm{Ø}}_3[（\mathrm{1个}-X）\mathrm{KBT}-（X）\mathrm{NBT}]$。与大多数铁电固溶体共同的逐渐演化不同，KBT-xNBT表现出从正常铁电基态到成熟的弛豫基态的突然跃迁。$X>0.58$。我们表明，这种突然过渡到弛豫态是由不相称的/高度无序的稳定引起的$\mathrm{中号}$遍历/顺电温度状态下的单点铁弹性变形。突然的交叉表现为由组分驱动的一些重要特性的异常变化，例如介电响应，机电特性，四方性和矫顽场，电应变，并模仿了组分驱动的铁电转换中经常遇到的情况。