AI 中文总结
该研究通过分子动力学模拟发现无铅固溶体多形相边界处的渗流多重分形极性畴主导压电响应，确立其为巨压电效应的微观机制，提出分形连通性可作为高性能压电材料的设计参数。
AI 中文摘要
铁电体中的巨压电效应通常与相边界不稳定性相关，其中多形相边界（PPB）是典型例子，传统上归因于铁电相的共存。本文采用无铅（K,Na）NbO₃-(Bi,Na)ZrO₃固溶体的大规模分子动力学模拟，发现PPB处存在渗流型多重分形极性畴，其主导介电和压电响应。通过量化该极性网络的整体分形维数和多重分形谱宽度，将分形连通性和多尺度异质性确定为PPB的微结构序参量。当分形畴体积分数接近三维渗流阈值时，可逆压电响应达到最大值，表明近临界极性连通性可实现巨可逆机电耦合。在此机制中，分形主干保留极性记忆并提供可逆性所需的回复力，周围非分形区域则提供大极化旋转和应变所需的极性柔量。这些结果确立了渗流型多重分形极性畴作为PPB增强压电性的微观机制，并提出分形连通性可作为高性能压电材料的设计参数。
英文摘要
Giant piezoelectricity in ferroelectrics is commonly associated with phase-boundary instabilities, among which the polymorphic phase boundary (PPB) is a prominent example conventionally attributed to the coexistence of ferroelectric phases. Here, using large-scale molecular dynamics simulations of the lead-free (K,Na)NbO3-(Bi,Na)ZrO3 solid solutions, we show that the PPB hosts a percolating multifractal polar domain which governs the dielectric and piezoelectric responses. By quantifying the global fractal dimension and multifractal spectrum width of this polar network, we identify fractal connectivity and multiscale heterogeneity as microstructural order parameters for the PPB. The maximum reversible piezoelectric response occurs when the fractal-domain volume fraction approaches the three-dimensional percolation threshold, suggesting that near-critical polar connectivity enables giant reversible electromechanical coupling. In this mechanism, the fractal backbone preserves polar memory and provides the restoring force required for reversibility, while the surrounding nonfractal regions supply the polar compliance needed for large polarization rotation and strain. These results establish percolating multifractal polar domains as a microscopic mechanism for PPB-enhanced piezoelectricity and suggest fractal connectivity as a design parameter for high-performance piezoelectrics.
Comments16 pages, 4 figures
