“…They are transformed to other phosphates by hydrolysis and dehydration reactions at high temperatures. [6][7][8] The presence of water molecules influences the intermolecular interactions (affecting the internal energy and enthalpy) as well as the crystalline disorder (entropy) and, hence, influences the free energy, thermodynamic activity, solubility, stability, and electrochemical and catalytic activities. [9][10][11][12] Studies on the thermodynamics, mechanisms, and kinetics of solid-state reactions are a challenging and difficult task with complexity resulting from the great variety of factors with diverse effects such as reconstruction of solid-state crystal lattices, formation and growth of new crystallization nuclei, diffusion of gaseous reagents or reaction products, heat conductance of materials, static or dynamic character of the environment, and physical state of the reagentssdispersity, layer thickness, specific area and porosity, type, amount and distribution of the active centers on solid state surface, etc.…”