Fluoride Model Systems: III, The System NaF–BeF2 and the Polymorphism of Na2BeF4 and BeF2
- 2 June 1953
- journal article
- Published by Wiley in Journal of the American Ceramic Society
- Vol. 36 (6) , 185-190
- https://doi.org/10.1111/j.1151-2916.1953.tb12864.x
Abstract
A revised equilibrium diagram is presented for the system NaF–BeF2, a weakened model of the system CaO–SiO2. The compound Na2BeF4 has four structural modifications corresponding to the γ, β, α', and α forms of Ca2SiO4. Inversion temperatures were found to be as follows: α→α’= 320°C., γ→α’= 225°C., α’→β (metastable) = 115°C. The quartz form of BeF2 was found to have a high‐low inversion at 220°C. The high‐quartz form exists in equilibrium with liquid in binary fluoride systems up to the melting temperature of BeF2, as closely as can be determined. The cristobalite form appears to have only a metastable existence, and a tridymite form has not been found. The compound NaBeF3 has a structure similar to β‐CaSiO3 below 343°C., with a different structure (not that of α‐CaSiO3) above this temperature.Keywords
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