Core–Shell KNbO 3 /BaTiO 3 With Coherent Interfaces: Dielectric Constant >1300 and Low Temperature/E‐Field Sensitivity

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ABSTRACT This study investigates the development of lead‐free dielectric ceramics with enhanced properties by creating a core–shell structure featuring coherent, nanoscale heteroepitaxial interfaces between the BaTiO 3 (BT) core and KNbO 3 (KN) shell. BT nanoparticles were coated with a KN shell using a wet chemical method, and the resulting KN/BT core‐shell particles were processed to circular pellets and then sintered in a reduced atmosphere to form dense nanocomposite ceramics with a relative density of ∼97%. The preservation of the core–shell architecture in the sintered KN/BT ceramics was directly confirmed by STEM and STEM–EDS elemental mapping, which revealed a well‐defined, coherent heteroepitaxial interface between the BT core and the KN shell. The nanocomposite ceramics exhibited a high dielectric constant exceeding 1300, with significantly reduced temperature and electric‐field dependence (X8R‐level stability) compared to pure BT‐core ceramics. This enhanced performance is attributed to the engineered interface between the BT core and KN shell, which creates structural gradient regions and suppresses domain switching. The slim, nearly linear polarization‐electric‐field response, with maximum and remanent polarizations of 14 and 0.93 µC/cm 2 , respectively, at an applied electric field of 100 kV/cm and minimal electric‐field‐induced strain (< 0.03%), further demonstrates the unique properties arising from the core–shell structure. These functional gains are attributed to interface‐driven elastic clamping by coherent KN shells and SGRs rather than heavy elemental doping, offering a promising route to high‐dielectric constant, field‐stable, lead‐free dielectrics for capacitor applications.

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