Barium Titanate Tin Oxide as a Versatile Lead‐Free Material for Advanced Energy Applications

In the global pursuit of environmentally benign and high‐performance materials, barium titanate tin oxide (Ba (Ti₁₋ x Sn x ) O₃ or BTS) has emerged as a prominent lead‐free ferroelectric ceramic. Its remarkable dielectric, piezoelectric, and electrocaloric properties, tunable across a wide range via precise compositional modification (i.e., adjusting the Sn substitution level, x, and co‐doping with rare‐earth or transition‐metal ions), position it as a key candidate for a new generation of energy applications. This article provides a structured scientific overview of the significant advancements in the research of BTS. The novelty of this study lies in its timely synthesis of the very latest breakthroughs—including the recent achievement of ultrahigh piezoelectricity surpassing PZT—and its systematic connection of these state‐of‐the‐art findings to the material's fundamental properties. We focus on scalable synthesis routes, the intricate relationship between microstructure‐phase‐composition and functional properties, and BTS's promising role in high‐density energy storage devices, efficient electrocaloric cooling systems, high‐sensitivity piezoelectric sensors, and a growing range of biocompatible biomedical and photocatalytic environmental technologies.