RU2579390C1 - METHOD OF PRODUCING CADMIUM TETRABORATE CdB4O7 - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to production of polycrystalline borates, which can be used as a solid-state matrices for efficient luminophores. For producing cadmium tetraborate CdB₄O₇ by thermal treatment of initial components used are a mixture of CdO (31.03 wt%), H₃BO₃ (68.97 wt%). Process is carried out on air with stepped lifting temperature from 300-850°C for 250 hours.

EFFECT: invention enables to obtain monophase polycrystalline cadmium tetraborate CdB₄O₇ without pelletisation of sample.

1 cl, 1 dwg, 2 tbl, 1 ex

Description

The invention relates to the field of materials science, in particular, to a method for producing polycrystalline borates, which can find application as solid-state matrices for effective phosphors.

Known methods for producing cadmium tetraborate CdB ₄ O ₇ .

(1. Whitaker A., Channell AD Phase Equilibria in the System CdO - ZnO - B ₂ O ₃ at 850 ° C // J. Materials Science. 1993. Vol. 28., No. 9. P. 2489-2493.

2. Ihara M., Krogh - Moe J. Crystal Structure of Cadmium Diborate CdO · 2B ₂ O ₃ . // Acta Crystallographica. 1966. Vol. 20. P. 132-134.

3. Hart P.B., Steward E.G. Compound Formation in the System Cadmium Oxide - Boric Oxide // J. Inorganic Nuclear Chemistry. 1962. Vol. 24. No. 6. P. 633-634.)

The disadvantage of these methods for producing cadmium tetraborate CdB ₄ O ₇ is the non-uniformity of the resulting product.

Closest to the claimed invention is a method for producing a polycrystalline sample of cadmium tetraborate CdB ₄ O ₇ , synthesized by solid-phase reactions from chemically pure cadmium oxide with a content of the main substance (99.5%) and boric acid (99.8%). The corresponding quantities of the starting materials were mixed, crushed into a fine powder in acetone medium and pressed into tablets with a diameter of 1.25 cm at a pressure of 6000 lbin ^-2 (1 lbin ^-2 = 7.0307 · 10 ² kg / m ^-2 ). The tablets were first annealed at 400 ° C for 30 minutes. Then, the annealing temperature was increased to 750 ° C and held for 160-170 hours, and then raised to 850 ° C. The authors of [1] note that it was not possible to obtain a pure phase of the Cd ₂ B ₄ O ₇ composition; traces of the Cd ₂ B ₂ O ₅ compound were present in the sample. Difficulties in obtaining a sample of CdB ₄ O _{7 were} also reported in other works.

(4. Lonsdale T.D., Whitaker A. Phase Equilibria in the System CdO - B ₂ O ₃ -SiO ₂ at 800 ° C // J. Materials Science. 1978. Vol. 13. No. 7. P. 1503- 1508.

5. Whitaker A., Pike MG Phase Equilibria in the System CdO - B ₂ O ₃ -GeO ₂ // J. Materials Science. 1978. Vol. 13. P. 2321-2327.

6. ICDD PDF-2 Data Base: Cards # 01-071-2169).

A disadvantage of the known synthesis method is the need for tabletting the sample.

The purpose of the invention is the development of a method for producing monophasic polycrystalline cadmium tetraborate CdB ₄ O ₇ .

This goal is achieved in that as the starting reagents in the preparation of CdB ₄ O ₇ , a mixture of CdO: H ₃ BO _{3 is used} , which is subjected to a multi-stage heat treatment in air at a temperature rise of 300 to 850 ° C for 250 hours.

The invention is illustrated by the following example.

Example. A mixture of CdO weighed 1.6669 g (31.03 wt.%) And H ₃ BO _{3 with a} weighed 3.7096 g (68.97 wt.%) Was thoroughly triturated in an agate mortar in ethyl alcohol. The resulting mixture was annealed in a platinum crucible in air at a temperature of 300, then 500, 650, and 850 ° C for 10, 30, 50, and 160 hours, respectively (a comparison of the synthesis modes is presented in Table 1).

The starting materials were: cadmium oxide of the qualification “special grade” and boric acid H ₃ VO _{3 of the} grade “pure grade”. Preliminarily, cadmium oxide CdO was calcined at 600 ° C for 5 hours to constant weight.

The completeness of the reaction was monitored by x-ray diffraction [automatic powder diffractometer D8 Advance Bruker AXS (Cu K _α radiation, graphite monochromator)]. An X-ray diffraction pattern of the obtained CdB ₄ O ₇ compound is shown in the drawing. The unit cell parameters of CdB ₄ O ₇ (space group Pbc) were refined using the least squares method (LSM) using ICDD PDF-2 Data Base card index data [6]. The crystallographic characteristics of cadmium tetraborate are given in table. 2. An X-ray diffraction pattern of the obtained compound CdB ₄ O ₇ was indicated in a rhombic syngony with sp. Gr. Pbca.

Using the proposed method for producing cadmium tetraborate provides the following advantages in comparison with existing methods.

As a result of using a mixture of the starting components of cadmium oxide CdO - 31.03 wt.% And boric acid H ₃ BO ₃ - 68.97 wt.%, A single-phase cadmium tetraborate CdB ₄ O ₇ was obtained, which is synthesized without additional tabletting of the sample.

Using the claimed invention allows to obtain cadmium tetraborate CdB ₄ O ₇ , which can be proposed as a solid-state matrix for effective phosphors.

Brief Description of the Drawings

FIG. - radiographs of CdB ₄ O ₇ : (a) - our data; (b) - data [2].

Claims (1)

A method of producing cadmium tetraborate CdB ₄ O ₇ by heat treatment, characterized in that as the starting components use a mixture of CdO (31.03 wt.%), H ₃ BO ₃ (68.97 wt.%) With a stepwise rise in temperature from 300 to 850 ° C for 250 hours

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