Crystallization Kinetics of Sodium Zincogermanate Na2ZnGeO4
Sodium germanates and zincogermanates have recently been synthesized in the Na2O-ZnO-GeO2-H2O system at high temperatures and pressures and converted into the form of crystals with a variety of compositions. Some of these compounds had never been detected before, for example, the crystalline phase of composition Na2ZnGeO4, provisionally named phase D . Crystals of this phase are formed at 200–250°C at pressures corresponding to autoclave occupation factors of 50–80% in sodium hydroxide solutions with concentrations of 5 wt.% or over. In the concentration range 5–15 wt.% NaOH, the phase crystallizes together with certain other crystalline phases; for concentrations of over 15 wt.%, only the crystals of phase D are formed over the whole temperature and pressure range studied. The original charge employed for the synthesis incorporated the chemical reagents zinc oxide (chemically pure and especially pure), and germanium dioxide (especially pure).
KeywordsTemperature Drop Alkali Solution Caustic Soda Interplane Distance Dissolution Zone
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