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 0.5 Na 0.5 TiO 3 -based ceramics cannot be increased simultaneously has not been solved. In this work, (1- x )Bi 0.5 Na 0.5 TiO 3 - x BaNi 0.5 Nb 0.5 O 3 (BNT- x BNN, x  = 0, 0.02, 0.03, 0.04 mol) lead-free ceramics were prepared by conventional solid-state reaction method. Introduction of BaNi 0.5 Nb 0.5 O 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- x BNN 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.