A study by researchers at Tokyo Tech introduces a significant advancement in fuel cell technology, focusing on protonic ceramic fuel cells (PCFCs). The study identifies hexagonal perovskite-related Ba5R2Al2SnO13 oxides as materials with exceptional proton conductivity and thermal stability, essential for the development of next-generation fuel cells. These materials allow for full hydration and high proton diffusion, making them promising candidates as electrolytes for PCFCs that can operate at intermediate temperatures without degradation. The study led by Professor Masatomo Yashima showcases the high proton conductivity of Ba5Er2Al2SnO13 material, attributing it to its unique crystal structure and full hydration in oxygen-deficient environments. The material exhibited a conductivity of 0.01 S cm⁻¹ at 303 °C, showcasing its potential for practical applications. Moreover, the material demonstrated chemical stability under various annealing conditions, highlighting its robustness for continuous operation. The discovery of Ba5R2Al2SnO13 oxides opens new possibilities for the development of efficient and durable fuel cells that can operate at lower temperatures. This breakthrough could pave the way for the commercialization of cleaner energy production through protonic ceramic fuel cells.