Microwave-Assisted Synthesis of (C ₁₂ H ₂₅ NH ₃ ) ₂ MnCl ₄ Layered Perovskite: A Fast, Reliable, and Scalable Route for Solid–Solid Thermal Energy Storage Applications

Solid-solid Phase Change Materials (PCMs) offer key advantages over solid-liquid systems, including improved thermal conductivity, stability, and safety. Among these, organic-inorganic hybrid perovskite compounds are particularly promising for thermal energy storage applications due to their competitive energy density and tunable phase transitions. However, their synthesis is typically time-consuming and difficult to scale. This study introduces microwave-assisted (MWA) synthesis as a rapid and scalable approach to prepare bis-(dodecylammonium) tetrachloromanganate [(C₁₂H₂₅NH₃)₂MnCl₄], marking its first application to this material class. Compared to conventional solvothermal (ST) synthesis, the MWA method reduced reaction time by 75%, increased phase transition enthalpy by 7.9%, and delayed complete thermal breakdown by 20 °C. Characterization using XRD, FTIR, DSC, and TGA confirmed enhanced crystallinity and thermal performance. Additionally, the material was directly compacted into mechanically stable pellets by pressure sintering (PS), without the need for binders, enabling practical applications such as integration into thermal storage modules. These findings support a sustainable and scalable route for fabricating (C₁₂H₂₅NH₃)₂MnCl₄ as a high-performance solid-solid PCM for thermal energy storage.