SU1728150A1 - Material for optical coating - Google Patents

Abstract

This invention relates to high quality optical coating materials. In order to improve the quality of coatings by increasing heat resistance, expanding the transparency range, reducing absorption coefficients and light scattering, the material contains, mol%: tantalum pentaoxide 80-90, hafnium dioxide 10-20. The material was synthesized from hydrochloric acid solutions of tantalum and hafnium salts by the method of co-precipitating hydroxides with further drying and calcining of solid solutions in air. When exposed to temperatures of 420-450 ° C for 3-4 hours, the coating is not destroyed, the transparency range is 0.32 to 12.1 µm; absorption coefficient (1-3). 10%, light scattering coefficient (0.04-0.07)%. 1 tab.

Description

The invention relates to optical materials with low light loss, high thermal stability in vacuum and can be used in the development of structures with internal mirrors.

A known optical material based on tantalum pentoxide, which is the prototype of the claimed invention. Optical coatings of tantalum pentoxide have a sufficiently high refractive index (n 2.05-2.10) in the visible spectral range, high climatic and mechanical strength (group 1) and are used in the design of optical products operating under normal climatic conditions ( t 25-30 ° C, humidity 80%), as well as in a vacuum. However, this material has the following disadvantages: a dispersion of the refractive index is observed; high absorption coefficient (8 -), as a result of which significant light loss occurs in

films made from tantalum pentoxide; limited transparency area (up to 8 microns); low temperature resistant coating (4 250 ° C); a limited range of optical transparency (up to 9 microns), which does not allow it to be used to create mirrors that work in a 10.6 micron laser system; high absorption coefficient (1.6); low thermal resistance of the material (the coating is destroyed at a temperature of 250 ° C); high light scattering (0.5–0.8%). The essential differences of the proposed material are as follows. The use of hafnium dioxide as an additive to a known material (tantalum pentoxide) leads to the formation of evaporating solid solutions in the tantalum pentaoxide – hafnium dioxide system, which leads to an increase in the transparency region, a decrease in the absorption coefficients and light scattering, and an increase in the thermal stability of the coatings.

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The percent ratios of the components are determined experimentally and are limited by the region of existence of azeotropic solid solutions of hexagonal structure. Outside of the claimed concentrations, solid solutions having the above properties do not exist. Solid solutions of the proposed material are synthesized from hydrochloric acid solutions of tantalum and hafnium salts by the method of co-precipitating hydroxides with further drying and calcining the obtained solid solutions on air at 1350–1400 ° C.

P . To obtain 100 g of film-forming material with a content of 90 mol.% TaaOs and 10 mol.% HN2, 47 ml of a 100 g / l solution of hafnium oxychloride are added to 475 ml of an alcohol solution of 200 g / l tantalum pentachloride on hafnium dioxide, the solution is diluted with distilled water at a volume ratio of 1: 4 and, with stirring, tantalum hydroxides and hafnium hydroxides are co-precipitated with a dilute ammonia solution (1: 1) to a pH of 8.5-9.0. The suspension is filtered, the hydroxide precipitate is washed from the mother liquor with distilled water and dried at 100-150 ° C for 24 hours. The dried precipitate is ground and calcined at 1000-1100 ° C for 4 hours. Under these conditions, water is completely removed and a solid solution of tantalum pentoxide with hafnium dioxide of the desired solution is formed. To make a compact material, it is pressed under a pressure of 3-4 kgf / s in the form of tablets with a diameter of 20-40 mm and a height of 5-10 mm at 1350-1400 ° C for 4-6 hours.

PRI mme r.2. To obtain 100 g of film-forming material with a content of 85 mol.% Ta20bi 15 mol.% HUa, 78 ml of a solution of hafnium oxychloride with a concentration of 100 g / l of hafnium dioxide was added to a molten alcohol solution of tantalum with a concentration of 200 g / l for tantalum pentoxide. Further work is carried out analogously to example 1.

Trickly, To obtain 100 g of film-forming material with a content of 80 mol% TaaOsM 20 mol% HN2, a solution of tantalum pentoxide with a concentration of 200 g / l was added to a 447 ml alcohol solution of tantalum pentachloride with a concentration of 200 g / l.

hafnium oxychloride with a concentration of 100 g / l for hafnium dioxide. Further work is carried out, similarly to example 1.

Optical coatings sold from

of the proposed materials, applied by the method of electron beam evaporation at the URM 3.279060 installation at the sputtering rate of the material 4–7 A ° / s, the residual pressure in the chamber 1 mm Hg. Art. Coatings are applied on substrates of quartz, K-8, KU-1 glass and metallic germanium at a substrate temperature of 160-180 ° C. The resulting layers are tested for heat resistance, which is determined by the visual method.

(cracking, delamination of coatings). The light loss (absorption and light scattering coefficients) is determined by an opto-acoustic method. The spectral characteristics of the optical coatings of the proposed materials are measured on an SF-8 spectrophotometer. The chemical composition of the proposed materials and the comparative characteristics of optical coatings of the proposed material and the known are presented in the table. The proposed material as compared with the known one has the following advantages: a wider range of optical transparency (up to 12 µm), which makes it possible to use the material in a system with a laser,

operating at a wavelength of 10.6 microns; low absorption coefficient (up to 1); low light scattering coefficient (0.04-0.08); high temperature resistance (450 ° C) in vacuum.

The economic effect of using the invention is expected by improving the quality of optical coatings, which is achieved by increasing the transparency range, reducing light losses,

increase thermal resistance of the material.

Claims (1)

Claims of the invention The material for optical coatings, including tantalum pentaoxide, characterized in that in order to improve the quality of coatings by increasing heat resistance, expanding the range of transparency, reducing absorption coefficients and light scattering, it additionally contains hafnium dioxide in the following ratio of mol%: Tantalum pentaoxide80-90 Hafnium dioxide 10-20.