CS252917B1 - Method for raw material preparation for triglycine sulphate's monocrystals' cultivation - Google Patents

Abstract

Method of preparing raw material for growing single crystals of triglycine sulphate providing growing perfect single crystals with reproducible habit and properties by the release of triglycine sulfate inorganic ions by recrystallization twice from redistilled water, down purified by paraelectric crystallization phase over Curie Tc = 49 ° C in the presence of ethyl alcohol and / or isopropyl alcohol.

Description

The invention relates to a process for the preparation of a high purity raw material for the cultivation of triglycine sulfate single crystals.

One of the decisive factors in the cultivation of triglycine sulphate raonocrystals is the quality of the use of the growing compound, which is synthesized by the action of sulfuric acid on aminoacetic acid - glycine in an aqueous medium and subsequent recrystallization of the excreted salt (GH ₂ IJH ₂ .C00H)

In many cases, however, the raw material thus prepared is not particularly satisfactory in terms of reproducibility of the cultivation cycles due to the high sensitivity of the triglycine sulfate monocrystals to trace impurities, in particular based on organic compounds. The triglycine sulfate single crystal is limited by a number of natural growth areas, each characterized by a different partition coefficient for each impurity. Absorption of impurities on individual surfaces influences their growth rates or even blocks their growth. This results in changes in crystal habit, which in most cases differ for each cultivation cycle. In addition, pyroelectric properties are not standardized. These random impurities which dope the crystal causing the above complications can be of two kinds. On the one hand, these are inorganic ions, of which only paramagnetic cations strongly influence pyroelectic properties.

These are mainly chromium, ferric, manganese and the like. on the other hand, organic compounds whose influence on pyroelectric properties depends on the size of their own dipolmoment and their content in the material. The partition coefficient for organic compounds in this case is given by steric effects and is related to the structures of dopants.

252 917

A third possibility of influencing the properties of triglycine sulfate single crystals is the combination of the above impurities, which differs substantially from cases where the crystal is doped with only one type of impurities, and this effect cannot be practically estimated. If the concentrations of impurities in the order of 10 ” ² “10“ ““ “% cause observable changes in crystal properties, it is practically impossible to reliably determine the presence of organic impurities and thus less their structure.

As far as inorganic impurities are concerned, it can be assumed, based on neutron activation analysis, that their total content after double recrystallization of the feedstock from redistilled water does not in any case exceed tens of ppm, of which only paramagnetic ions are ppm. Their influence can therefore practically be ruled out.

In the case of organic impurities whose presence cannot be determined analytically precisely and which is manifested in the instability of the habit of the cultivated monocrystals and their properties, they have not been removed by the known methods of purification.

These drawbacks are eliminated by a method of preparing raw material for growing single crystals triglycinsulfátu according to the invention whose principle consists in that Triglycine, free of inorganic impurities twice recrystallized from redistilled blows the water is further purified Recrystallization of paraelectric phase above the Curie temperature T _{R T} = 49 ° C in the presence ethyl alcohol and / or isopropyl alcohol.

From the raw material thus prepared, it is possible to grow quality monocrystals of triglycine sulphate, showing strong growth anisotropy in the polar axis b. basal areas are minor.

Example 1

1300 g of triglycine sulfate crystallized twice from redistilled water was dissolved in 3000 ml of redistilled water at 80 ° C, filtered through a 0.6 µm filter and at 75 ° C added 1200 ml of ethyl alcohol at a time. Temperature

2S2 917 increased spontaneously by the released crystallization heat.

After stirring for 1 h, the temperature dropped to 65 ° C, the product was aspirated, washed with 30% alcohol and then with pure alcohol.

The yield was 1150 g of raw material. The monocrystals grown from this raw material had defined reproducible habitus and reproducible properties. When monocrystals were grown under otherwise identical conditions from a raw material that was treated only twice by recrystallization from redistilled water, they had a diverse habitus, they germinated and their properties were not reproducible.

Example 2

The procedure was analogous to Example 1 except that 1600 g of triglycine sulphate twice crystallized from redistilled water was taken to work and 1200 ml of isopropyl alcohol were further used and cooled to 53 ° C. The yield was 1400 g of raw material and the single crystal results were similar to those of Example 1.

Claims (1)

A method for preparing raw material for growing single crystals triglycinsulfátu, wherein triglycinsulřát freed from inorganic ions by recrystallization twice from doubly distilled water is further purified by crystallization in a paraelectric phase above the Curie temperature T _c «49 ° C in the presence etylalkohblu and / or isopropanol.