1：Experimental Design and Method Selection:

The study used sol-gel chemistry to prepare the core-shell composite, involving the synthesis of precursor sols for BNT-BT

2：08 and CoFe2O4, followed by coating, calcination, and sintering. Sample Selection and Data Sources:

Samples were prepared from chemical reagents provided by Sigma-Aldrich, with no external datasets used.

3：List of Experimental Equipment and Materials:

Equipment included a PANalytical Empyrean diffractometer, FEI QUANTA INSPECT F SEM, TecnaiTM G2 F30 S-TWIN TEM, Quantum Design MPMS-5S SQUID magnetometer, 4194A Impedance/Gain-phase Analyzer, and Agilent Technology AFM/PFM Model

4：Materials included bismuth(III) acetate, sodium acetate, barium acetate, titanium(IV) isopropoxide, cobalt acetate, iron nitrate, citric acid, and solvents like acetic acid and ethanol. Experimental Procedures and Operational Workflow:

54 BNT-BT

5：08 precursor sol was prepared by dissolving acetates in acetic acid and adding titanium isopropoxide stabilized with acetylacetone. CoFe2O4 sol was prepared from iron nitrate and cobalt acetate with citric acid. BNT-BT08 powder was calcined at 650°C, coated with CoFe2O4 sol, centrifuged, dried, and calcined at 700°C. Pellets were sintered at 1100°C. Characterization involved XRD, SEM, TEM, magnetic hysteresis measurements, dielectric property measurements, and PFM. Data Analysis Methods:

XRD data were analyzed using Rietveld refinement. Dielectric properties were measured with an impedance analyzer, and magnetic properties with a SQUID magnetometer. Data analysis included fitting patterns and interpreting hysteresis loops.