RU1820885C - Process for preparing composite fluorides - Google Patents

Abstract

The dry recrystallized nitrate salts of barium, lanthanum, aluminum and sodium are mixed with a 5-fold excess of 40-41% hydrofluoric acid, and the starting aluminum and sodium salts take 10% more of the stoichiometric due to the solubility of the resulting / fluorides in excess of HP. The reaction mass is defended, the precipitate is separated, washed, dried at 80-100 ° C, calcined at 400-450 ° C in the presence of ammonium fluoride in the ratio of the charge: NH ,, The product is obtained with the composition 21BaP2-21 aPz-4A1Pz- 20 # P or 21BaF2-4LaP2-2AIF3-20NaF. 2 s.p. crystals, 4 tab.

Description

The invention relates to the field of producing fluorides of complex composition used to produce fluoride glass in fiber optics.

An object of the invention is to provide a product suitable for the manufacture of fluoride glass.

The goal is achieved by a method of producing fluorides of complex composition 21BaP2-2LaF3-4AIF3-20NaF and 21BaPa-41aPz-2AIF3-20NaF, comprising & contacting the recrystallized dry nitric acid starting salts with 40-41% hydrofluoric acid and calcining the product in the presence of ammonium fluoride in the ratio of the mixture: NH4P g1: 2 at 400-500 ° C for 1.5-2 hours.

The essence of the process is as follows: when coprecipitating complex fluorides with a 5-fold excess of a 40-41% solution of hydrofluoric acid, micro-impurities are purified. By calcining complex fluorides with ammonium fluoride at 400-450 ° C, an anhydrous product is obtained that does not have oxygen-containing impurities.

The choice of the charge composition is related to the structural features of the optical fibers consisting of a 63ZrF4-21BaF2-2LaF3-4AIF3-20NaF sheath and a 63ZrF4-21BaF2-4LaF4-2AIF3-20NaF core. The fluorides of a complex composition obtained by this method are one of the purest materials for the manufacture of fluoride glass and can be recommended for fiber optics.

Example Dry recrystallized barium nitrate salts in an amount of 54.4 g, lanthanum - 8.6 g, aluminum - 16.5 g and sodium - 18.5 g are placed according to stoichiometry in a fluoroplast-4 reactor. Pour a 5-fold excess of the stoichiometric required 40-41% hydrofluoric acid brand OSH in the amount of

ate

with

00

u o

00 00 SP

s

183.8 ml. Excess HF is taken to completely precipitate fluorides of complex composition and to purify them from trace metals. The mixture is mixed with a mechanical stirrer also of PTFE-4 during this time. After settling, the mother liquor is decanted, the precipitate is washed repeatedly with a 3% solution of hydrofluoric acid to remove MoO3 ions and 2 times with ethyl alcohol to speed up the drying time and obtain a free-flowing powder. The product is dried at 80-100 ° C with an infrared lamp. Drying at this temperature allows mainly alcohol and water to be removed. After drying, fluorides of complex composition are calcined at 400-450 ° C in the presence of ammonium fluoride in the ratio iuHxra: NH4F 1: 2. The selected calcination temperature is necessary to completely remove gaseous HF.

Tables 1 and 2 give the main parameters of the proposed method.

Table 3 shows the composition of microimpurities in complex fluorides, which was controlled by a spectral analysis method.

For complete precipitation of complex fluorides, a holding time of 5-6 hours has been selected. If the holding time of the reacting components is less than 5 hours, for example 4 hours, the complex fluorides do not correspond to the indicated compositions. Elemental analysis of complex fluorides (mol.%):

Example 1. (19ВаР2-1.51аРз-3,4А1Рз-18NaF) -3HF

Example 2. (l9BaF2-3.5LaF3-1.6AIF3-18NaF) 3HF

When the exposure time is more than 4 hours, for example 5 hours, the fluoride compositions correspond to the claimed:

Example 1. (21BaF2-2LaF3-4AIF3-20NaF) -2HF

Example 2. (21BaP2-4CaPz-2A1Pz-20NaF) 2HF.

The aging of the reactive components of the batch is necessary to purify the synthesis products from microimpurities of heavy metals, which adversely affect the quality of the fiber. When the exposure time is extended beyond 6 hours, for example 7 hours, the chemical composition of the complex fluorides remains unchanged.

At a selected drying temperature of 80-100 ° C, the product is freed from traces of alcohol and water. If the products are dried at a temperature below 80 ° C, for example 70 ° C, the drying process is extended by 18 hours, therefore, additional fluoride contamination takes place and traces of H.F. remain in the synthesis products.

Elemental analysis of complex fluorides corresponds to the following compositions (mol.%).

Example 1. (21BaP2-21 aPz-4A1Pz-20NaF) 1.5HP.

pt; er p 2. (21BaP2-4 aPz-2A1Pz-20NaF) -1.5HF.

When the drying temperature rises to 120 ° C, the products sinter, lose their flowability and become lumpy.

The selected calcination temperature at 400-450 ° C is necessary to decompose NH4F and completely remove gaseous HP. At temperatures below 400 ° C, for example 350 ° C, the calcination process is extended to 3h.

5 and a small amount of HP remains in the synthesis products. Elemental analysis of fluorides corresponds to the following compositions (mol.%). Example. (21ВаР2-21аРз-4А1Рз-20NaF) 0.5HF.

0 Example 2. (21ВаР2-41 аРз-2А1Рз-20NaF) 0.5HF,

Calcination at a temperature of 400-450 ° C makes it possible to obtain products corresponding to the claimed compositions.

5, when the products of synthesis are calcined above 450 ° C, for example 510 ° C, the decomposition of the main product is accompanied by pyrohydrolysis.

Table 4 shows the predetermined composition of the elements in fluoride suitable for the manufacture of fluoride glass, as well as the composition of the elements in fluoride obtained by this method.

Thus, this method allows to obtain fluorides of complex composition suitable for the manufacture of fluoride glass in fiber optics.

Claims (3)

The claims 0 1. A method of producing fluorides of complex composition, including processing a mixture of salts of the corresponding metals with hydrofluoric acid with stirring, settling the reaction mixture, separation 5 0 sediment from the solution, washing the precipitate first with a solution of hydrofluoric acid, and then with an organic solvent, drying and calcining the product, heating and so that, in order to provide the possibility of obtaining a product suitable for for the manufacture of fluoride glass, dry, pre-crystallized, nitric salts of barium, lanthanum, aluminum and sodium are taken as salts, treatment with 5 salt mixtures is carried out with 40-41% hydrofluoric acid, taken in excess, followed by exposure of the reaction mixture for 5 -6 hours, and calcining is carried out in the presence of ammonium fluoride at a mass ratio of a mixture of salts and ammonium fluoride equal to 1: 2. 2. A method according to claim 1, characterized in that drying is carried out at 80-100 ° C, and calcination is carried out at 400-450 ° C. 3. The method according to claim 1, characterized in that the nitrate salts of aluminum and sodium take 10% more stoichiometrically necessary. The results of a chemical analysis of complex fluorides, May. % Table 1 table 2 Table 3 Table 4