In situ formation of Yb2Ti2O7 secondary phase at grain boundaries for synergistically enhanced resistance against reduction and dielectric stability in BaTiO3 ceramics

This study proposes a novel grain-boundary engineering strategy that synergistically enhances both resistance against reduction and dielectric stability in BaTiO₃-based ceramics sintered under reducing atmosphere. By constructing uniform 2–3 nm Yb₂O₃ coatings on 100 nm BaTiO₃ particles via chemical co-precipitation, we achieve in situ formation of Yb₂Ti₂O₇ pyrochlore phases at grain boundaries during sintering. Unlike conventional solid-state processed counterparts, the grain-boundary-confined Yb₂Ti₂O₇ phases exhibit dual functional mechanisms: Zener pinning-induced ultrafine grain refinement, and lattice mismatch-generated compressive stress that stabilizes the pseudocubic phase. These coupled effects synergistically elevate carrier migration activation energies, enabling ultrahigh resistivity (7.91 ×10¹⁰ Ω·cm) and exceptional resistance against reduction. Simultaneously, the synergy between stress and the grain structure refines ferroelectric domains to the nanoscale, thereby activating strong relaxor behavior that enhances dielectric stability. Consequently, the engineered ceramic simultaneously delivers X7R-compliant thermal stability (ε_25℃=1623, tanδ =0.76 %) and minimal DC bias dependence (∆εᵣ/ε₀ = 4.2 % at 0–2 V/µm).