Heat‐to‐Electricity Conversion Using Barium Strontium Titanate Multilayer Capacitors

ABSTRACT Pyroelectric materials are attractive for converting heat into electricity, yet the best performance is obtained with lead‐containing ceramics, remaining a major environmental concern. Here, we address this problem by developing lead‐free barium strontium titanate multilayer capacitors (Ba 0.65 Sr 0.35 Ti 0.998 Mn 0.002 O 3 MLCs). A maximum energy density of 3.7 J cm −3 is achieved under an applied field of 300 kV cm −1 across a 170 K temperature span in an Olsen electro‐thermodynamic cycle. We conducted Olsen cycles with two approaches: electric displacement‐electric field ( D‐E ) loops and stepwise control of temperatures and voltages, which provide consistent results. In addition, we found that Ba 0.65 Sr 0.35 Ti 0.998 Mn 0.002 O 3 MLCs show a second‐order ferroelectric–to‐paraelectric (FE‐to‐PE) phase transition, which shifts to higher temperatures by the applied electric field. This provides a broad and practical temperature window for low‐grade waste heat recovery. Our study shows that the performance of pyroelectric energy harvesting in barium strontium titanate materials is comparable to their conventional lead‐based counterpart (3.6 J cm −3 in lead scandium tantalate in similar conditions), revealing the promising prospects of sustainable energy recovery applications.