RU2786691C1 - Terahertz crystalline ceramics of the tlbr0.46i0.54 -agi system - Google Patents

Abstract

FIELD: new terahertz elements.

SUBSTANCE: invention relates to a new terahertz (THz) element base for the range of 0.1-10.0 THz based on optical halide crystalline materials, which can be used for the manufacture by extrusion of a new class of flexible nanocrystalline light guides resistant to UV and radiation and intended for as a transmission channel not only for terahertz radiation, but also for infrared, as well as for the production of optical products by hot pressing - windows, lenses, prisms, films intended, along with light guides, for use in THz optics and photonics, laser and IR technology, in space and nuclear technologies. According to the invention, a terahertz crystalline ceramic of the TlBr_0.46I_0.54 - AgI system is proposed, including a solid solution of monovalent thallium bromide-iodide of the composition TlBr_0.46I_0.54 and a silver halide, characterized in that the terahertz crystalline ceramic is made on the basis of a solid solution of TlBr_0.46I_0.54 and contains silver iodide (AgI) as silver halide in the following ratio of components, mol.%: TlBr_0.46I_0.54 solid solution - 57÷82 and silver iodide - 43÷18.

EFFECT: invention provides formation of plastic and non-hygroscopic THz ceramics of micro- and nanocrystalline structure resistant to ultraviolet (UV), apparently, and ionizing radiation.

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Description

The invention relates to terahertz (THz) materials, namely, to a new halide class of micro-nanocrystalline optical ceramics and single crystals based on silver halides and monovalent thallium highly transparent in the terahertz (THz) range from 0.1 to 10.0 THz, which corresponds to the optical range from 3000.0 to 30.0 μm [Terahertz crystals, Patents of the Russian Federation No. 2 756 582 of 01.10.2021, Patents of the Russian Federation No. 2 756 581 of 01.10.2021, Patents of the Russian Federation No. 2 756 580 of 01.10.2021, Patents of the Russian Federation No. 2 756 068 from 09/27/2021; RF patent 2762966 dated December 24, 2021 Method for producing highly transparent crystalline ceramics based on two solid solutions of the AgBr-TlI system (variants); RF patent 2758552 dated 10/29/2021 Method for producing highly transparent crystalline ceramics based on two solid solutions of the AgBr-TlBr _0.46 I _0.54 system (options)].

To create promising halide terahertz and infrared optical materials, it is extremely important to study thermodynamically new phase diagrams of melting of multicomponent systems. Establishing the existence of homogeneous regions at 298 K and determining the concentration ranges ensures the production of optical ceramics with a micronanocrystalline structure, as well as the growth of single crystals.

A terahertz crystal based on silver chloride and bromide is known, in which a solid solution of univalent thallium halides TlBr _0.46 I _0.54 is additionally introduced [Terahertz crystals, Patents of the Russian Federation No. long-term, as well as with a low yield into optical products (from 20 to 40%) compared to obtaining ceramics with a yield of up to 90%. The crystals are passed into the far IR region up to 50 μm (6 THz). It should be noted that a more extended terahertz range from 4.6 to 10.0 THz is important for practical development, which corresponds to the far infrared range from 65.0 to 30.0 μm.

The closest technical solution is the "Method for obtaining highly transparent crystalline ceramics based on two solid solutions of the AgBr-TlBr _0.46 I _0.54 system (options)" [RF Patent 2758552 dated 10/29/2021].

Ceramics was obtained on the basis of the studied new phase diagram of the AgBr-TlBr _0.46 I _0.54 system. A method has also been developed for obtaining highly transparent crystalline ceramics of a certain composition in accordance with the regions of existence of solid solutions at room temperature (298 K) in the left and right parts of the diagram [“Promising terahertz materials: crystals and ceramics”, L.V. Zhukova, D.D. Salimgareev, A. S. Korsakov, A. E. Lvov, textbook, 2020. - 308 p. ISBN 978-5-8295-0742-8]. Ceramics are transparent in the IR range, depending on the chemical composition from 1.0 to 40-50.0 μm, but for widespread use in THz optics and photonics, laser and IR technology, ceramics are needed that are transparent not only in the terahertz, but also in the visible region .

There is a problem in developing terahertz crystalline ceramics that are transparent in the THz range from 0.1 to 10.0 THz, as well as highly transparent without absorption windows in the visible (0.5 - 0.8 μm), near (0.8 - 2.5 micron), medium (2.5 - 25.0 micron) and far (25.0 - 65.0 micron) infrared regions, plastic, non-hygroscopic, radiation resistant, which is important for obtaining THz optical products and flexible , time-stable terahertz fibers by extrusion.

The solution to the problem is achieved by developing terahertz crystalline ceramics of the system TlBr _0.46 I _0.54 - AgI, including a solid solution of bromide - iodide of monovalent thallium composition TlBr _0.46 I _0.54 and silver halide, characterized in that terahertz crystalline ceramics made on the basis of a solid solution of TlBr _0.46 I _0.54 and contains silver iodide - AgI as a silver halide, in the following ratio, mol. %:

solid solution TlBr _0.46 I _0.54 - 57÷82;

silver iodide - 43÷18.

The essence of the invention lies in the fact that on the basis of the new phase diagram of the system TlBr _0.46 I _0.54 - AgI, presented in figure 1 (Fig. 1, Phase diagram of the system TlBr _0.46 I _0.54 - AgI), get for THz range (0.1 - 10.0 THz) new optical ceramics. To increase plasticity, expand the transmission range to the far IR region (30 - 65 μm), which corresponds to the high-frequency THz range (10.0 - 4.6 THz), into the crystal cubic lattice of the TlBr _0.46 I _0.54 solid solution (crystals KRS-5) introduced silver iodide in the following ratio of components, they say. %:

solid solution TlBr _0.46 I _0.54 - 57÷82;

silver iodide - 43÷18.

It should be noted that from KRS-5 single crystals (solid solutions of the composition TlBr _0.46 I _0.54 ) polycrystalline IR fibers are obtained by extrusion, which are destroyed due to recrystallization, which sharply limits their application. The introduction of silver iodide into KRS-5 crystals suppresses the recrystallization process and ensures the production of flexible, time-stable IR light guides.

Ceramics is non-hygroscopic (silver and monovalent thallium halides are insoluble in water), photoresistant (resistant to ultraviolet radiation at a wavelength of 260-370 nm), radiation-resistant to β- and γ-irradiation with doses from 500 to 1000 kGy and more (consists of radiation-resistant KRS-5 crystals), transparent up to 70% without absorption windows in the visible, near, middle and far infrared ranges from 0.5 to 65.0 μm (Fig. 2, Transmission spectra of ceramics based on the TlBr _0.46 I _{0 system, 54} - AgI) compared with the prototype from 1.0 to 40-50.0 μm.

Example 1

A high-purity charge (99.9999 wt %) was obtained for the synthesis of terahertz optical ceramics based on the components of the composition, in mol. %:

solid solution TlBr _0.46 I _0.54 - 57;

silver iodide - 43.

Staged drying of the mixture was carried out at a temperature of 120-180 °C, followed by remelting by the method of directional crystallization to obtain ceramics of a micro-nanocrystalline structure (Fig. 3, Structure of micro-nanocrystalline ceramics of the TlBr _0.46 I _0.54 - AgI system according to the results of scanning electron microscopy ). Samples were made by hot pressing to study the physicochemical properties, which confirms the plasticity of ceramics. By the same method, that is, by pressing at a temperature of 180-200 ° C and high pressures, optical products are obtained in special molds with an optical polished surface.

Transmission spectra were taken on a Shimadzu UV-1800 spectrophotometer (190 - 1100 nm); IR Fourier spectrometer IRPrestige-21, Shimadzu (1.28 - 41.7 µm); IR-Fourier spectrometer Vertex 80, Bruker. Ceramics is highly transparent without absorption windows in the visible region (0.5-0.8 µm), in the near (0.8-2.5 µm), middle (2.5-25.0 µm) and far (25.0- 65.0 µm) infrared regions (Fig. 2). In the terahertz range, ceramics are also highly transparent without absorption windows from 10.0 to 4.6 THz, since this range corresponds to the optical range from 30.0 to 65.0 µm.

The study of the radiation resistance of ceramics to β-irradiation with a gradual increase in dose from 50 to 400 kGy and more was carried out on a linear electron accelerator UELR-10-10S. Ceramics is resistant not only to β-radiation, but also to γ-irradiation with a dose of up to 1000 kGy, as well as to ultraviolet radiation at a wavelength of 260-370 nm.

Example 2

Terahertz ceramics of micro-nanocrystalline structure, ductile, non-hygroscopic, photo- and radiation-resistant, based on the TlBr _0.46 I _0.54 - AgI system, the composition of components in mol. %:

solid solution TlBr _0.46 I _0.54 - 82;

silver iodide - 18

received as in example 1.

The ceramic is highly transparent without absorption windows in a wide spectral range from 0.5 to 60.0 µm (Fig. 2). The terahertz range from 10.0 to 5.0 THz corresponds to the far infrared range from 30.0 to 60.0 µm.

Ceramics is resistant to ultraviolet, β- and γ-irradiation. The study was carried out as in example 1.

Example 3

Received terahertz ceramics, as in example 1, the composition of the components in mol. %:

solid solution TlBr _0.46 I _0.54 - 70;

silver iodide - 30.

It is plastic, non-hygroscopic, photo- and radiation-resistant, transparent without absorption windows in the terahertz range from 10.0 to 4.8 THz and in the optical range from 0.5 to 63.0 μm (Fig. 2).

It should be noted that according to the studied new phase diagram of the TlBr _0.46 I _0.54 - AgI system (Fig. 1), in which there is one phase based on a TlBr _0.46 I _0.54 solid solution doped in an amount from 0 to 18 mol. % silver iodide. Single crystals are grown in this range. The second rhombic phase based on Tl ₂ AgI ₃ begins to form upon the introduction of silver iodide from 18 to 43 mol. % into the crystal cubic lattice TlBr _0.46 I _0.54 . As a result, a micronanocrystalline ceramic structure is formed at low temperatures of 298 K (Fig. 3). With a further increase in AgI in the TlBr _0.46 I _0.54 solid solution, ceramics are not formed due to polymorphic transformations.

Technical result

A new terahertz micronanocrystalline ceramic of the TlBr _0.46 I _0.54 - AgI system has been developed, which belongs to a new halide class of terahertz materials and is intended not only for the manufacture of optical products (windows, lenses, films, etc.) by hot pressing. but also to obtain more flexible and time-resistant IR fibers by extrusion, in comparison with fibers from KRS-5 crystals. Ceramics has the following set of essential features:

- highly transparent in the terahertz, infrared and visible ranges,

- photo and radiation resistant,

- designed for the manufacture of optical products by the method of hot pressing, and by the method of extrusion of more flexible and time-resistant IR light guides,

which contributes to its wide application in terahertz optics and photonics, as well as in the creation of a new generation of laser fiber-optic systems in the infrared and terahertz range. The photo- and radiation stability of optical products and ceramic fibers ensure its application in space and nuclear technologies.

Claims (2)

Terahertz crystalline ceramics of the TlBr _0.46 I _0.54 - AgI system, including a solid solution of monovalent thallium bromide-iodide of the composition TlBr _0.46 I _0.54 and silver halide, characterized in that the terahertz crystalline ceramics is made on the basis of a solid solution of TlBr _{0 ,46} I _0.54 and contains silver iodide - AgI as silver halide in the following ratio of components, mol.%: solid solution TlBr _0.46 I _0.54 57÷82 silver iodide 43÷18

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