The Role Played By Me2+ in Hydrothermal Crystallization of Germanates of Divalent Metals

Chemical reactions between oxides of divalent metals and germanium in high-temperature alkaline solutions produce a large number of germanates differing in their composition and crystal structure. The specific compounds formed are determined by the physical- chemical conditions of synthesis (temperature, pH of the crystallization medium, solvent concentration, etc.) and by crystal-chemical factors which are most clearly revealed by the effects of the metals in the reactant oxides on the processes of the crystallization of germanates. This aspect is discussed in the present paper. The analysis of the phase diagrams given below takes into account structural crystal-chemical characteristics of individual components and makes it possible to formulate basic relationships for the formation of germanates of divalent metals, to find the roles played by mono- and divalent cations in the formation of final products of crystallization, and to reveal the general features characteristic of germanate systems.