Process for preparing essentially pure barium fluoride crystals

Details Process for preparing essentially pure barium fluoride crystals Process for preparing essentially pure barium fluoride crystals

1976-05-17

1977-10-11

Stern, Edward

Chemistry of inorganic compounds

Halogen or compound thereof

Binary fluorine containing compound

423430, 423395, C01F 1122, C01F 1136, C01F 1118, C01F 1138

Patent

active

040535720

ABSTRACT:
A malleable or press-forgeable ingot of barium fluoride, for use as an optical body, may be grown from an ultra-pure precipitate of barium fluoride which contains less than 10 parts per million (ppm) of strontium or calcium. A process is disclosed for crystallizing barium nitrate crystals in the presence of nitric acid, reacting barium nitrate with ammonium carbonate to form barium carbonate, recovering barium carbonate crystals, suspending the barium carbonate crystals in water and precipitating barium fluoride with hydrofluoric acid. The barium fluoride crystals are recovered, dried and then calcined in the presence of ammonium fluoride or bifluoride. Barium fluoride (BaF.sub.2) crystals obtained by the process of this invention contain less than 10 ppm of each strontium and calcium.
Crystals of an alkaline earth metal fluoride which have been calcined in the presence of a fluoride of ammonium are unexpectedly densified, and are particularly suited for melt-growth of an ingot in a known manner. A maximum concentration of 10 ppm of strontium and calcium in a BaF.sub.2 ingot has been found to be the critical demarcation between a frangible prior art BaF.sub.2 ingot and an ingot of BaF.sub.2 which does not unpredictably shatter when cut, and, which may be reliably press-forged into an optical body.

REFERENCES:
patent: 2703790 (1955-03-01), Anderson
patent: 3947553 (1976-03-01), Moss et al.
J. W. Mellor's, "A Comp. Treatise on Inorg. and Theo. Chem.", vol. 3, p. 688, Longmans, Green & Co.

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