Crystallization Behavior and Multiferroic Properties of Bi_3.15Nd_0.85Ti₃O₁₂/CoFe₂O₄ Powders Synthesized by Sol–Gel Method

Bi_3.15Nd_0.85Ti₃O₁₂ (BNdT)/CoFe₂O₄ (CFO) composite ceramic powders with embedded structures were successfully prepared by sol–gel processing. Their crystallization behavior was characterized by XRD, DTA, FT-IR, and HRTEM. The magnetic and ferroelectric phases of these composite ceramic powders segregate during calcination. The CFO phase forms easily at ~300°C, thereafter the BNdT matrix phase nucleates with grain growth at the CFO grain boundaries at temperatures >500°C. The CFO phase acts as a heterogeneous nucleation point for formation of the ferroelectric BNdT phase. Furthermore, the 0.5BNdT–0.5CFO composite ceramic powders go through a ferroelectric–paraelectric phase transition at 259°C, and the magnetic CFO nanoparticles (50–100 nm, under calcination at 600°C) embedded in the ferroelectric matrix, show superior magnetic behavior (M_max = 16.50 emu/g), comparable to pure CFO nanoparticles.