Effect of Fe substitution at the B-site on the pyroelectric properties of bismuth titanate ceramics

Abstract

The effect of the B-site substitution with the low-valent Fe ion on the properties of lead-free bismuth titanate (BNT) ferroelectric ceramics is explored. In this work, a series of ceramics with different Fe substitution concentrations are prepared. The Bi_0.5Na_0.5Ti_0.999Fe_0.001O₃ (BNTF-0.1) ceramic has the highest depolarization temperature (T_d ≈ 213°C). The dielectric constant and dielectric loss fluctuate slightly with decreasing frequency. The pyroelectric coefficient p appreciably increases from 2.25 × 10⁻⁴ C·m⁻²·K⁻¹ for BNT to 2.88 × 10⁻⁴ C·m⁻²·K⁻¹ for BNTF-0.1 at room temperature (RT). The figures of merit (FoMs) for BNTF-0.1 component have also been improved at RT, where current figure of merit (F_i) = 1.02 × 10⁻¹⁰ m V⁻¹, voltage figure of merit (F_v) = 3.51 × 10⁻² m² C⁻¹, and detectivity figure of merit (F_D) = 1.66 × 10⁻⁵ Pa^−1/2, which is attributed to its lower dielectric constant (∼330) and dielectric loss (∼0.0131). Between 20°C and 80°C, the values of the FoMs remain stable, with the F_D of BNTF-0.1 varying by only ±6.2%, indicating its superior temperature stability. These results confirm that low-cost Fe substitution is an available strategy for optimizing the performance of BNT-based ceramics. BNTF-x ceramics would be excellent candidates for lead-free pyroelectric infrared detection.