Rashchenko, Sergey V.; Bekker, Tatyana B.; Bakakin, Vladimir V.; Seryotkin, Yurii V.; Kokh, Alexander E.; Gille, Peter; Popov, Arthur I.; Fedorov, Pavel P.
A new mechanism of anionic substitution in fluoride borates.
In: Journal of Applied Crystallography, Vol. 46, No. 4: pp. 1081-1084
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A comprehensive study of the BaF2-Ba3(BO 3)2 phase diagram has revealed a significant difference between the two intermediate phases Ba5(BO3)3F and Ba 7(BO3)4-y F2+3y. The latter exhibited (BO 3)3- ↔ 3F- anionic substitution which, unusually, strongly influences the solidus temperature. A comparison of the Ba5(BO3)3F and Ba7(BO3)4-y F2+3y crystal structures, along with consideration of other compounds demonstrating (BO3)3- ↔ 3F- isomorphism, allows for the disclosure of the mechanism of (BO3)3- ↔ 3F - heterovalent anionic substitution in fluoride borates via [(BO 3)F]4- tetrahedral groups being replaced by four fluoride anions. No exception to this mechanism has been discovered among all known phases with (BO3)3- ↔ 3F- substitution.