Pyroelectric characteristics of lead-free materials: A systematic review

Pyroelectric materials, that generate electrical polarization in response to temperature fluctuations, are widely used in infrared detection, energy harvesting, and biomedical applications. However, environmental and health concerns associated with traditional lead-based materials, such as PZT and PMN-PT, have opened the new window of exploring sustainable lead-free alternatives. This systematic review comprehensively examines recent advancements in lead-free pyroelectric ceramics, focusing on their structural design, performance optimization, and key challenges. Promising materials, including bismuth sodium titanate (BNT), potassium sodium niobate (KNN), and sodium bismuth titanate (NBT)-based ceramics, exhibit competitive pyroelectric coefficients (up to 2720 µC/m²K) and thermal stability. Key strategies to enhance performance are; doping, phase boundary engineering, and porosity control, which significantly improve pyroelectric figures of merit (FOMs). For instance, La-doped BNT-BNN ceramics achieve a high pyroelectric coefficient (14.3 × 10⁻⁴C/m²K) with a depolarization temperature of 174 °C, while porous BaTiO₃-SnO₂ composites demonstrate a 47 % reduction in dielectric constant, enhancing detectivity. Despite these advancements, challenges such as high dielectric loss, thermal instability, and poling inefficiency also persist with these materials. These issues can be addressed through compositional tuning and microstructure optimization, that can enable lead-free materials to surpass conventional lead-based systems. This review provides a roadmap for lead-free pyroelectric technologies, emphasizing the balance between material properties as well as practical feasibility, further focussing on scalable synthesis, thermal endurance, and integration into functional devices to realize their full commercial potential.