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The formation of polar nanoregions through solid-solution additions is known to enhance significantly the functional properties of ferroelectric materials. Despite considerable progress in characterizing the microscopic behavior of polar nanoregions (PNR), understanding their real-space atomic structure and dynamics of their formation remains a considerable challenge. Here, using the method of dynamic pair distribution function, we provide direct insights into the role of solid-solution additions towards the stabilization of polar nanoregions in the Pb-free ferroelectric of Ba(Zr,Ti)O_{3}. It is shown that for an optimum level of substitution of Ti by larger Zr ions, the dynamics of atomic displacements for ferroelectric polarization are slowed sufficiently below THz frequencies, which leads to increased local correlation among dipoles within PNRs. The dynamic pair distribution function technique demonstrates a unique capability to obtain insights into locally correlated atomic dynamics in disordered materials, including new Pb-free ferroelectrics, which is necessary to understand and control their functional properties.

Weakly coupled relaxors based on compositions (1‐x) BaTiO3‐xBiMeO3, where Me is a metal ion, have attracted attention as potential candidates for high‐temperature high‐energy density capacitors. However, the necessary Bi content is typically high with x = 0.3‐0.4. In order to reduce problems associated with compatibility for base metal electrodes and due to additional problems due to Bi volatility, it is desirable to lower the Bi content in the overall composition for these materials. Here, we have explored a possible way to reduce BiMeO3 content through additional A‐site substitutions viz. Ca and Sn. The relaxor nature and energy storage properties of Sn‐modified (Ba,Ca)(Ti)O3‐BiScO3 ceramics were determined from their dielectric and ferroelectric behaviors. The material showed attractive properties in terms of a frequency‐independent (200 Hz‐1 MHz) dielectric response from room temperature to 200°C, extremely low loss and high‐energy storage efficiency. The structural phenomena underlying the functional properties of Sn‐modified (Ba,Ca)TiO3‐BiScO3 are characterized from temperature‐dependent X‐ray diffraction and pair distribution function analysis. In broader terms, the study illustrates the potential for tailoring relaxor behavior in Pb‐free ferroelectrics by combining phenomena, such as quantum fluctuations and lone pair stereochemical effect associated with different solid‐solution substitutions.

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