Phase transformations in perovskites La$_{0.6}$Ca$_{0.4}$Mn$_{1-y}$Co$_y$O$_{3\pm\delta}$ under the action of hydrogen

The structural and phase transformations of La$_{0.6}$Ca$_{0.4}$Mn$_{1-y}$Co$_y$O$_{3\pm\delta}$ ($y$ = 0.2 – 0.6) solid solutions in a reducing atmosphere were studied using in situ XRD and HRTEM methods. Experiments have shown that heat treatment in a reducing atmosphere of H$_2$ leads to the partial decomposition of solid solutions, the nature of which differs from decomposition in an inert atmosphere. In the case of a system with a hydrogen-containing atmosphere, the heterogeneous reduction of the structure leads to the formation of an orthorhombic phase of LaMnO$_3$-based perovskite with disordered vacancies, an additional phase of ordered Rudlesden–Poppertype perovskite based on La$_2$CoO$_4$ and Co and Ca$_2$MnO$_4$ nanoparticles on the surface of perovskite. In an environment with excessive partial oxygen pressure for the reduced sample, the reverse phase transition of the Rudlesden–Popper phase into the perovskite phase occurs.