Work

Simultaneous enhancement of piezoelectric coefficient and depolarization temperature in BF-BT-based ceramics via heterogeneous structure design

Year: 2026

Type: article

Abstract: BiFeO 3 –BaTiO 3 (BF-BT) lead-free ceramics are promising candidates for high-temperature piezoelectric applications due to their high Curie temperature ([Formula: see text]), but they typically suffer from a low depolarization temperature ([Formula: see text]) and a trade-off between piezoelectric coefficient ([Formula: see text]) and thermal stability. In this work, a sandwich structured composite 0.67BiFeO 3 –0.33BaTiO 3 –0.1 wt%MnO 2 /0.75BiFeO 3 –0.25BaTiO 3 –0.1 wt%MnO 2 /0.67BiFeO 3 –0.33BaTiO 3 –0.1 wt%MnO 2 (abbreviated as 33/25/33BFBT) ceramics (abbreviated as 33/25/33BFBT) consisting of two high-[Formula: see text] 0.67BiFeO 3 –0.33BaTiO 3 –0.1 wt%MnO 2 layers (abbreviated as BF-33BT) and a high-[Formula: see text] 0.75BiFeO 3 –0.25BaTiO 3 –0.1 wt%MnO 2 layer (abbreviated as BFBT) was designed to overcome this limitation. During high-temperature sintering, Ba[Formula: see text] ions diffused from the outer BF-33BT layers into the middle BFBT layer. This diffusion generated a Ba[Formula: see text] concentration gradient and formed diffuse layers on both sides of the ceramic. As a result, local heterogeneous structures were established within the composite. X-ray diffraction and Rietveld refinement revealed lattice expansion and an increased tetragonal phase fraction (from 31.5% to 44.9%) due to the substitution of smaller Bi[Formula: see text] by larger Ba[Formula: see text]. The heterogeneous structure enhanced relaxor behavior (diffusivity [Formula: see text] increased from 1.297 to 1.507), leading to a higher dielectric constant at [Formula: see text] and broader dielectric peaks. As a result, the 33/25/33BFBT ceramics achieved a [Formula: see text] of 140 pC/N (compared to 104 pC/N for the homogeneous BFBT ceramic) and a significantly increased [Formula: see text] of 420°C (from 300°C). Moreover, an in-situ[Formula: see text] of 365 pC/N was retained at 323°C. The improved performance is attributed to the presence of the diffuse layer, which contains polar nanoregions, reduced domain sizes, and defect-induced internal bias fields that suppress depolarization. This work demonstrates that constructing local heterogeneous structures via A-site ion diffusion is an effective strategy to simultaneously achieve a large [Formula: see text] and high [Formula: see text] in BF-BT-based ceramics, providing new guidance for designing high-temperature lead-free piezoelectrics.

Source: Journal of Advanced Dielectrics

DOI: 10.1142/s2010135x26500207