Novel AgNbO3-based lead-free ceramics featuring excellent pyroelectric properties for infrared detecting and energy-harvesting applications via antiferroelectric/ferroelectric phase-boundary design

Abstract

AgNbO₃ is considered as one of the most promising alternatives for lead-containing antiferroelectric (AFE) ceramics, and has been drawing progressively more attention. The AFE/ferroelectric (FE) phase-boundary design based on AgNbO₃ is very attractive and is a promising means to develop lead-free high-performance pyroelectric materials. In the present study, compounds with a high tolerance factor and high average electronegativity difference and LiNbO₃-type composition were proposed as being able to stabilize the FE phase of AgNbO₃. Ceramics with the composition (1 − x)AgNbO₃–xLiTaO₃ (ANLT) (x = 0–0.10) were designed and fabricated using the conventional solid-state method for pyroelectric applications. The effects of the LiTaO₃ content, temperature, and electric field on the phase-transition behavior of the ANLT system were investigated systematically. Based on our results, a composition–temperature phase diagram of the ANLT system was proposed, confirming the existence of the AFE/FE phase boundary. The depolarization and pyroelectric properties of the ANLT system were also studied. It was found that the x = 0.05 composition at the AFE/FE phase boundary had a large room-temperature pyroelectric coefficient (3.68 10⁻⁸ C cm⁻² K⁻¹) and exhibited excellent figures of merit for infrared detectors due to its low relative permittivity (252 at 1 kHz). Moreover, an ultrahigh pyroelectric energy density (1.4 J cm⁻³) was harvested using an Olsen cycle for the x = 0.5 composition, which was several times larger than that of other ceramic systems reported recently. These results suggest the ANLT ceramic would be an attractive multifunctional material for applications in infrared detectors and energy harvesting.