Enhanced pyroelectric properties of BNT-xBNN lead-free ferroelectric ceramics for energy harvesting

Pyroelectric energy harvesting has been explored to obtain high room temperature pyroelectric coefficient ( p) along with high depolarization temperature ( T _d) for the practical applications. However, the problem that T _d and p of Bi _0.5Na _0.5TiO ₃-based ceramics cannot be increased simultaneously has not been solved. In this work, (1- x)Bi _0.5Na _0.5TiO ₃- xBaNi _0.5Nb _0.5O ₃ (BNT- xBNN, x = 0, 0.02, 0.03, 0.04 mol) lead-free ceramics were prepared by conventional solid-state reaction method. Introduction of BaNi _0.5Nb _0.5O ₃ can facilitate lattice cell expansion and decrease of the O-B-O bond angles, providing more possibilities for the B-site ion to deviate from the equilibrium position, producing micrometer level grain size (3.25–6.15 µm) with good ferroelectric performance ( P _r = 42 μC/cm ², P _s = 47 μC/cm ²). The permittivity ( ε _r) of pristine samples raises from 439 to 723 when the content of BNN ascends to 0.03 mol. Hence, an enhanced room temperature p of 7.91 × 10 ⁻⁴ C m ⁻² K ⁻¹ with a high T _d of about 150 °C has been attained in BNT- xBNN with x = 0.03 mol, which concomitantly generates the energy density of 22.3 μJ/cm ³ with 90 MΩ load. Our work contributes to the development of pyroelectric properties for practical applications in energy harvesting.