Molten salt route to Ruddlesden-Popper calcium manganites

The selective synthesis of crystalline phases with a particular chemical composition is a challenging task. Calcium manganites (CaO(CaMnO₃)_m) are a sub-family of Ruddlesden-Popper perovskites, where m represents the number of perovskite-like layers separated by rock salt-like CaO layers. In this work, we demonstrate the applicability of molten salt synthesis for the preparation of various Ruddlesden-Popper calcium manganite phases. Using a mixture of NaCl and KCl as a flux and varying synthesis temperature, phase-pure Ca₂MnO₄ was obtained at a remarkably low temperature of 700 °C. At the same time, CaMnO₃, Ca₃Mn₂O_7, and Ca₄Mn₃O₁₀ required higher temperatures and contained varying levels of impurities. The prepared samples demonstrated a distinctive particle shape with a size in the micrometer range. Magnetic measurements revealed that all calcium manganites exhibit low-temperature antiferromagnetic properties, with a ferromagnetic component in the cases of CaMnO₃ and Ca₄Mn₃O₁₀.