Mechanochemical synthesis of fluorinated perovskites KCuF and KNiF3

A solvent-free mechanochemical synthesis of two fluorinated perovskites, KCuF3 and KNiF3, including the optimization of milling time at constant rotational speed, was studied as a practical and green alternative to the classical solvothermal synthesis. The presence of KCuF3 and KNiF3 in the desired crystalline phase as the main product was observed after 6 h of milling. At higher milling times K2CuF4 and K2NiF4 were detected as additional crystalline phases for the Cu- and Ni- based perovskites, respectively. The fluorinated perovskites were characterized by using X-Ray Powder Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM), confirming the selective formation of the fluorinated perovskites. The mechanochemical route was also compared to a new mild solvothermal method. An evaluation of the environmental impact and the energy efficiency was performed; moreover, the effectiveness of the mechanochemical process was compared to that of the solvothermal method. The promising results obtained from this innovative method opened the door to the use of solvent-free mechanochemical syntheses as a suitable approach in the field of crystal engineering also.