Enhanced Electrical Property and Thermal Stability in Lead-Free BNT–BT–BF Ceramics

The synergistic combination of outstanding electrical properties and exceptional thermal stability holds significant implications for advancing piezoelectric ceramic applications. In this work, lead-free ((1−x)(0.94Bi0.5Na0.5TiO3-0.06BaTiO3)-xBiFeO3 (x = 0.08, 0.10, 0.12)) ceramics were synthesized using a conventional solid-state method, with systematic investigation of phase evolution, microstructural characteristics, and their coupled effects on electromechanical performance and thermal stability. Rietveld refinement analysis revealed a rhombohedral–tetragonal (R–T) phase coexistence, where the tetragonal phase fraction maximized at x = 0.10. This structural optimization enabled the simultaneous enhancement of piezoelectricity and thermal resilience. The x = 0.10 composition achieved recorded values of d33 = 132 pC/N, g33 = 26.11 × 10−3 Vm/N, and a depolarization temperature Td = 105 °C. These findings establish BiFeO3 doping as a dual-functional strategy for developing high-performance lead-free ceramics.