RU2606229C1 - Complex lithium-lanthanum hafnate as luminescent material for conversion of monochromatic laser radiation and method for production thereof - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to novel compounds of sensitised phosphors based on inorganic crystalline compounds, specifically to complex lithium-lanthanum hafnate composition Li₇La_3-x-y-z-nNd_xHo_yEr_zDy_nHf₂O₁₂, where x=2.5⋅10^-2-1⋅10^-1, y=1.6⋅10^-7-4.7⋅10^-7, z=1.5⋅10^-6, n=1.2⋅10^-6-4.7⋅10^-6. Also disclosed is a method for production thereof.

EFFECT: obtained composition is used as luminescent material for conversion of monochromatic laser radiation at wave length 808 nm into a series of emission lines 2–2,3 mcm, 2,5–2,9 mcm, 3,1–3,35 mcm.

2 cl, 3 dwg, 3 ex

Description

The invention relates to new compounds of the class of sensitized phosphors based on inorganic crystalline compounds, specifically to complex REE activated hafnates of lithium-hafnium, and can be used to convert exciting monochromatic laser radiation with a wavelength of 808 nm into a series of emission lines of 2-2.3 μm, 2.5 -2.9 μm, 3.1-3.35 μm short-wave (1-3 μm) IR range.

Tellurite glasses doped with erbium, holmium and neodymium ions of the composition 70ТеО ₂ -20ZnO-9.0СаО-0.6Er ₂ O ₃ -0.1Ho ₂ O ₃ -0.3Nb ₂ O _{3 are} known as luminescent material with radiation in the near and middle IR range (Y. Zhang, L. Sun, Y. Chang, W. Li, C. Jiang. "Multiband infrared luminescence of Er ³⁺ -Ho ³⁺ -Nd ³⁺ / Tm ³⁺ - codoped telluride glasses", Front. Optoelectron . 2014, 7 (1): 74-76). The material is intensively excited in the IR region with a wavelength of 808 nm and generates simultaneous radiation with wavelengths of 1.53, 1.80, 2.10, 2.70 and 3.00 μm. Known luminescent material can be obtained by melting the starting components in an alundum crucible at 800-900 ° C in an electric resistance furnace with silicon carbide heaters, holding the molten material for 3 hours at 100 ° C and cooling.

A disadvantage of the known material is the use of tellurium oxide, which is a toxic compound (maximum concentration in the air, ~ 0.0070.01 mg / m ³ ) as the main component in the synthesis.

A known luminescent material based on a crystal with a garnet structure, the composition of which is expressed by the formula (A, But) ₃ B ₂ C ₃ O ₁₂ , where A is at least one of the elements of the group Y, La, Ce, Gb, Lu, Sc, Tb Eu; B is one of the elements of the group Sc, Ga, In, Lu, Al, Gb, Yb, Y, Cr, Tb, Eu; C - Ga or a mixture of Ga and Al, moreover, the amount of Al is not more than half of the mixture, while the Ho content is from 0.025 f. up to 2.95 fu, and additionally the material contains at least one of the elements of the group Li, Be, B, Na, Ca, Mg, Si, K, Ti, V, Μn, Fe, Co, Ni, Cu, Zn, Ge, Rb, Sr, Zr, Nb, Mo, W, Ta, Hf, Bi (patent RU 2095900, IPC H01S 3/16, 1996). The laser generates at several Stark sublevels of the ⁵ I ₆ → ⁵ I ₇ transition (transitions of the Ho ³⁺ ion). The generation wavelengths are: 2.842; 2.888; 2.926; 2.973; 2.973; 3.057 microns.

The material can be obtained by annealing the mixture of components in a platinum crucible for 10 hours at 1200 ° C and melt the tablets in an iridium crucible in a sealed chamber in an atmosphere of 98 vol. N ₂ + 2 about. O ₂ followed by drawing the crystal from the melt with a volume of 300 cm ³ at a speed of 4 mm / h. and a crystal rotation frequency of 40 rpm, and after the growth of the grown crystal from the melt, the crystal was gradually cooled to room temperature over 40 hours.

A disadvantage of the known luminescent material is that stimulated emission was obtained only in the range of 2.80-3.1 μm. The synthesis of the known material is time-consuming and based on the method of drawing from the melt, which requires long-term high-temperature annealing and long-term cooling.

Known as a laser material with radiation in the mid-IR range is a material based on a mixture of various components with molar percentages: (55-x)% GeO ₂ -20% Al ₂ O ₃ -20% BaF ₂ -4% Na ₂ O-1 % ErF ₃ -x% NdF ₃ at x = 0.5% (G. Bai, L. Tao, K. Li, L. Hu, Y. Hong Tsang. “Enhanced light emission near 2.7 um from Er-Nd co-doped germanate glass ", Optical Materials 35 (2013) 1247-1250). The material has a luminescence range in the wavelength range 2.5–2.9 μm with a peak at 2.7 μm (transition ⁴ I _11/2 → ⁴ I _13/2 of the Er ³⁺ ion) excited by a 808 nm diode laser. Known material can be obtained by melt the mixture of the starting components in a crucible of Pt-Au alloy at 1300 ° C for 30 minutes, followed by exposure of the molten material at 500 ° C for 2 hours

A disadvantage of the known laser material is the production of stimulated radiation at only one wavelength of 2.7 μm. Another disadvantage is the high temperature synthesis of the material.

Thus, the authors were faced with the task of developing the composition of the luminescent material, which allows expanding the range of conversion of monochromatic radiation from a near-infrared laser to short-wave infrared radiation.

The problem is solved by using a new chemical compound of complex lithium-lanthanum hafnate with a garnet structure of tetragonal modification of the composition Li ₇ La _3-xyzn Nd _x Ho _y Er _z Dy _n Hf ₂ O ₁₂ , where x = 2.5⋅10 ^-2 -1⋅10 ^-1 , y = 1.6⋅10 ^-7 -4.7⋅10 ^-7 , z = 1.5⋅10 ^-6 , n = 1.2⋅10 ^-6 -4.7⋅10 ^-6 as a luminescent material for converting monochromatic laser radiation with a wavelength 808 nm in a series of emission lines 2-2.3 microns, 2.5-2.9 microns, 3.1-3.35 microns.

The problem is also solved in a method for producing a luminescent material of the composition Li ₇ La _3-xyzn Nd _x Ho _y Er _z Dy _n Hf ₂ O ₁₂ , where x = 2.5⋅10 ^-2 -1⋅10 ^-1 , y = 1.6⋅10 ^{- 7} -4.7⋅10 ^-7 , z = 1.5⋅10 ^-6 , n = 1.2⋅10 ^-6 -4.7⋅10 ^-6 , which includes obtaining the initial mixture of stoichiometric amounts of oxides of the corresponding metals, previously calcined at a temperature of 900-910 ° С, and lithium carbonate taken in excess of 7-10%, its intensive mixing and abrasion with the addition of ethyl alcohol, pressing, heating to a temperature of 900-910 ° C with a heating rate of 30-35 deg / min and holding at that temperature for 5-5.2 hours, after which the resulting product is quickly removed and placed in liquid nitrogen with a holding time of 1-2 minutes, then kept in a dry atmosphere under normal conditions, after which the product is re-knitted, pressed, heated to a temperature of 960-980 ° С with a heating rate of 30-35 deg / min, incubated at this temperature for 5-5.2 hours and again placed in liquid nitrogen with an exposure of 1-2 minutes.

Currently, luminescent material of the proposed composition with a sensitizer from Nd ³⁺ and activators from Ho ³⁺ , Er ³⁺ , Dy ^{3+ is} not known from the patent and scientific literature, which allows the conversion of monochromatic radiation with a wavelength of 808 nm into a series of emission lines 2-2.3 microns, 2.5-2.9 microns, 3.1-3.35 microns, as well as the method for its preparation.

One of the traditional methods for converting near-infrared radiation to short-wavelength infrared radiation is based on the use of excitation and deexcitation effects of an activator located in an optical matrix. Upon excitation, the activator changes from the ground state to the excited state, followed by non-radiative relaxation from the excited state to the metastable state and, finally, the radiative transition from the metastable state to the ground state with short-wave infrared radiation. One of the effective activators in such processes is Ho ³⁺ , Er ³⁺ , Dy ⁺³ . However, in this case, to generate radiation, for example, at a wavelength of 2.7 μm (transition ⁴ I _11/2 → ⁴ I _13/2 of the Er ³⁺ ion), it is necessary to increase the lifetime at the upper level 4I _11/2 , which is achieved by increasing Er concentration up to 30 at. % In laser active media having several metastable levels, generation on several laser channels is possible. In particular, a situation is possible when the final level of one channel is the initial level of another or these levels are associated with non-radiative relaxation. Such a generation scheme is called cascade.

The authors of the proposed technical solution during experimental studies of the properties of a new chemical compound of complex lithium-lanthanum hafnate with a garnet structure of Li ₇ La _3-xyzn Nd _x Ho _y Er _z Dy _n Hf ₂ O ₁₂ found that Nd effectively absorbs laser radiation in this the optical matrix acts as a sensitizer of rare-earth ions Ho, Er, Dy (see Fig. 1). For Nd ^{3+, it is} most efficient to carry out excitation into the ⁴ F _5/2 absorption band by radiation with a wavelength of about 808 nm. The transition from the excited ⁴ F _5/2 level to the metastable ⁴ F _3/2 level is non-radiative, and the transition from the ⁴ F _3/2 level to the ⁴ I _15/2 , ⁴ I _13/2 , ⁴ I _11/2 levels is accompanied by the appearance of a series of lines in the IR range with maxima in the wavelength region of 1.7-1.9 μm, 1.25-1.45 μm, 1.00-1.13 μm, respectively. The transition from the ⁴ F _3/2 level to the ⁴ I _9/2 level with a peak radiation value at ~ 0.9 μm is not in the range of measured wavelengths.

At the same time, due to the small difference in energy between the Nd ³⁺ ( ⁴ F _3/2 ) and Er ³⁺ ( ⁴ I _9/2 ) levels, energy from the excited Nd ³⁺ ( ⁴ F _3/2 ) level is transferred to the Er ³ level ⁺ ( ⁴ I _9/2 ) (ΕΤ1, see Fig. 1). The transition from the excited Er ³⁺ ( ⁴ I _9/2 ) level to the metastable Er ³⁺ ( ⁴ I _11/2 ) level is nonradiative, and the transition from the Er ^{3+ 4} I _11/2 ion level to the ⁴ Ι _13/2 level is accompanied by the appearance of a line in the short-wave infrared range with a maximum in the wavelength range of 2.5–2.9 μm. Due to the small difference in energies between the Er ³⁺ ( ⁴ I _13/2 ), Ho ³⁺ ( ⁵ I ₇ ) and Dy ³⁺ ( ⁶ Н _11/2 ) levels, the energy from the Er ³⁺ ( ⁴ I _{13 / 2} ) is transferred to the levels of Ho ³⁺ ( ⁵ I ₇ ) and Dy ³⁺ ( ⁶ Н _11/2 ) (ET2 and ET3, see Fig. 1). The transition from the excited Dy ³⁺ ( ⁶ Н _11/2 ) level to the metastable level of Dy ³⁺ ( ⁶ Н _13/2 ) is non-radiative, and the transitions from the excited Ho ³⁺ (5Ι ₇ ) and Dy ³⁺ ( ⁶ Н ₁₃ ) levels _{/ 2} ) to the Ho ³⁺ (5I ₈ ) and Dy ³⁺ ( ⁶ Н _15/2 ) levels, respectively, are accompanied by the appearance of a series of lines in the short-wave and mid-IR range with maxima in the wavelength range of 2-2.3 μm and 3.1-3.35 μm .

The authors first obtained a new chemical compound - a solid solution of the composition Li ₇ La _3-xyzn Nd _x Ho _y Er _z Dy _n Hf ₂ O ₁₂ , where x = 2.5⋅10 ^-2 -1⋅10 ^-1 , y = 1.6⋅10 ^-7 -4.7⋅10 ^-7 , z = 1.5⋅10 ^-6 , n = 1.2⋅10 ^-6 -4.7⋅10 ^-6 .

The studies conducted by the authors led to the conclusion that the solid solution composition Li ₇ La _3-xyzn Nd _x Ho _y Er _z Dy _n Hf ₂ O ₁₂ , where x = 2.5 =10 ^-2 -1⋅10 ^-1 , y = 1.6⋅10 ^-7 -4.7⋅10 ^-7 , z = 1.5⋅10 ^-6 , n = 1.2⋅10 ^-6 -4.7⋅10 ^-6 , has the best luminescent properties that allow it to be used as a luminescent material for conversion monochromatic radiation with a wavelength of 808 nm in a series of emission lines 2-2.3 μm, 2.5-2.9 μm, 3.1-3.35 μm (see Fig. 2, which shows the concentration dependences of emission in Li ₇ La _3-xyzn Nd _x Ho _y solid solutions Er _z Dy _n Hf ₂ O ₁₂ when excited and radiation with λ _ex = 808 nm). The concentration dependences of the luminescence intensity of Li ₇ La _3-xyzn Nd _x Ho _y Er _z Dy _n Hf ₂ O ₁₂ solid solutions have a maximum in the region x = 2.5⋅10 ^-2 -1⋅10 ¹ (see Fig. 3, where concentration dependences of the luminescence intensity of Li ₇ La _3-xyzn Nd _x Ho _y Er _z Dy _n Hf ₂ O ₁₂ solid solutions at a - 1.043 μm (transition ⁴ F _3/2 → ⁴ I _11/2 of the Nd ³⁺ ion), b - 1.318 μm (transition ⁴ F _3/2 → ⁴ I _13/2 of the Nd ³⁺ ion), c - 1.846 μm (transition ⁴ F _3/2 → ⁴ I _15/2 of the Nd ³⁺ ion), g - 2.106 μm (transition ⁵ I ₇ → ⁵ I ₈ of the Ho ³⁺ ion), d - 2.658 μm (transition ⁴ I _11/2 → ⁴ I _13/2 of the Er ³⁺ ion), е - 3.168 μm (transition ⁶ Η _13/2 → ⁶ H _{15 / 2} Dy ions ³⁺ )). At x <2.5⋅10 ⁻² , luminescence “flares up”; at x> 1⋅10 ⁻¹ , concentration quenching occurs.

As the studies conducted by the authors showed, heating the mixture of the starting reagents to 900–910 ° С and holding at this temperature for 5–5.2 hours lead to the beginning of the formation of Li ₇ La _3-xyzn Nd _x Ho _y Er _z Dy _n Hf ₂ O phases ₁₂ tetragonal modification of lanthanum oxide (La ₂ O ₃ ) and lanthanum hafnate (La ₂ Hf ₂ O ₇ ). Further heating at a higher temperature (960–980 ° C) with a short-term treatment of samples removed from the furnace in liquid nitrogen leads to the complete formation of compounds of the composition: Li ₇ La _3-xyzn Nd _x Ho _y Er _z Dy _n Hf ₂ O ₁₂ tetragonal modification without impurities of lanthanum oxide (La ₂ O ₃ ), lithium hafnate (Li ₂ HfO ₃ ) and lanthanum hafnate (La ₂ Hf ₂ O ₇ ). Heating to temperatures below 900 ° C and holding for less than 5 hours are insufficient to start the formation of the Li ₇ La _3-xyzn Nd _x Ho _y Er _z Dy _n Hf ₂ O ₁₂ phase and lead to the formation of a mixture of lanthanum hafnate (La ₂ Hf ₂ O ₇ ) lanthanum oxide (La ₂ O ₃ ) and lithium carbonate (Li ₂ CO ₃ ). Heating to temperatures above 980 ° C and holding for more than 5.2 hours lead to the formation of impurities of lithium hafnate (Li ₂ HfO ₃ ) and lanthanum hafnate (La ₂ Hf ₂ O ₇ ). Lithium carbonate (Li ₂ CO ₃ ) was taken with an excess of 7-10%, taking into account the volatility of Li when heated, taking an excess of less than 7% leads to the formation of impurities of lithium hafnate (Li ₂ HfO ₃ ) and lanthanum hafnate (La ₂ Hf ₂ O ₇ ) taking an excess of more than 10% leads to an unreasonable overspending of lithium carbonate. Preliminary pressing and holding in liquid nitrogen for 1-2 min of heat-treated tablet samples taken out of the furnace prevent the formation of these impurities, which are easily formed by slow cooling of the powder mixture. In order to obtain clean samples, namely, to prevent the possibility of aluminum entering the compound when the walls of the alundum crucible come into contact with the sample and the formation of La ₂ Hf ₂ O ₇ and Li ₂ HfO ₃ impurities on the tablet surface, we made additional thin tablets 10 mm in diameter and a thickness of 2-2.5 mm on the bottom of the alundum crucible and on top of the main tableted sample.

Thus, the authors propose a new chemical compound of the composition Li ₇ La _3-xyzn Nd _x Ho _y Er _z Dy _n Hf ₂ O ₁₂ , where x = 2.5⋅10 ^-2 -1⋅10 ^-1 , y = 1.6⋅10 ^-7 -4.7⋅10 ^-7 , z = 1.5⋅10 ^-6 , n = 1.2⋅10 ^-6 -4.7⋅10 ^-6 , as a luminescent material, which makes it possible to convert monochromatic radiation with a wavelength of 808 nm into a series of emission lines 2-2.3 microns, 2.5-2.9 microns, 3.1-3.35 microns, and a method for its preparation.

The proposed complex hafnate of lithium-lanthanum with the structure of a tetragonal garnet of the composition Li ₇ La _3-xyzn Nd _x Ho _y Er _z Dy _n Hf ₂ O ₁₂ , where x = 2.5⋅10 ^-2 -1⋅10 ^-1 , y = 1.6⋅10 ^-7 -4.7⋅10 ^-7 , z = 1.5⋅10 ^-6 , n = 1.2⋅10 ^-6 -4.7⋅10 ^-6 , can be obtained as follows. As starting compounds for the synthesis, oxides of lanthanum (La ₂ O ₃ ), neodymium (Nd ₂ O ₃ ) of qualification (chemically pure) calcined at 850-900 ° C for 4-5 hours, in which they are present as impurities, are used But ³⁺ , Er ³⁺ , Dy ³⁺ in an amount of 1⋅10 ^-6 -4.5⋅10 ^-3 mass. %, hafnium oxide (Hf ₂ O ₃ ) (analytical grade), lithium carbonate (Li ₂ CO ₃ ) (analytical grade). Weighed portions of hafnium oxide, weighed in stoichiometric amounts, are mixed with calcined oxides of lanthanum, neodymium and lithium carbonate taken in excess of 7-10%, taking into account the volatility of Li upon heating. The mixture of reagents is thoroughly abraded in an agate mortar with the addition of a few drops of ethyl alcohol and pressed. Tablets of the main substance are prepared with a diameter of 10 mm and a height of 5-10 mm, and additionally thin tablets are prepared from the same mixture for laying on the bottom of the alundum crucible and on top of the main tabletted sample also with a diameter of 10 mm and a height of 2-2.5 mm. Next, the pressed samples are placed in alundum crucibles with a height of 35 mm and an inner diameter of 27 mm, then heated at 900-910 ° C and kept at this temperature for 5-5.2 hours. The heating rate is 30-35 deg / min. The samples obtained after heating are quickly removed from the oven, immersed in a vessel with liquid nitrogen and kept for 1-2 minutes until cooling, then transferred to glass containers with a lid and stored in a dry, closed desiccator, that is, in a dry atmosphere under normal conditions. After remixing, the samples are pressed again, heated to 960–980 ° C with a heating rate of 30–35 deg / min, kept in an oven for 5–5.2 hours, and the cooling procedure is repeated similarly to the previously indicated. After batching, powder samples are subjected to x-ray phase and structural analyzes, and their physicochemical properties are examined. The obtained products according to x-ray phase, structural and chemical analyzes are single-phase compositions that correspond to the formula Li ₇ La _3-xyzn Nd _x HO _y Er _z Dy _n Hf ₂ O ₁₂ , where x = 2.5⋅10 ^-2 -1⋅10 ^-1 , y = 1.6⋅10 ^-7 -4.7⋅10 ^-7 , z = 1.5⋅10 ^-6 , n = 1.2⋅10 ^-6 -4.7⋅10 ^-6 , and have a garnet structure of tetragonal modification. The average crystallite size according to scanning electron microscopy is ~ 2.4-3.2 μm.

The proposed method is illustrated by the following examples.

Example 1

As starting reagents take: 3.0406 g HfO ₂ (analytical grade); 3.4710 g La ₂ O ₃ (chemically pure) (mixed with Nd ³⁺ , But ³⁺ , Er ³⁺ , Dy ³⁺ in the amount of 1.2⋅10 ^-3 , 2⋅10 ^-6 , 5⋅10 ^-5 , 1⋅10 ^-6 mass%) and 0.06076 g (Nd ₂ O ₃ ) (chemically pure) (mixed with La ³⁺ , But ³⁺ , Er ³⁺ , Dy ³⁺ in an amount of 8⋅10 ^-3 , 4⋅10 ^-4 , 5⋅10 ^-5 , 4.5⋅10 ^-3 wt.%), Preliminarily calcined at 900 ° С for 4 h, 2.0580 g of Li ₂ CO ₃ (chemically pure) with an excess of lithium 10 % Next, the samples are intensively mixed, abraded in an agate mortar with the addition of a few drops of ethyl alcohol, and subjected to pressing under a pressure of 3000 kg / cm ² . As a result, 2 large tablets are prepared with a height of 5 mm and a diameter of 10 mm and two thin tablets with a height of 2-2.3 mm, which are necessary for laying on the bottom of the alundum crucible and on top of the main tableted sample. Next, the pressed sample is placed in an alundum crucible with a height of 35 mm and an inner diameter of 27 mm and then placed in the SNOL-E5CC furnace, heated to 910 ° C and held for 5 hours. The heating rate is 30 deg / min. The tablet sample obtained after heat treatment is quickly removed from the furnace and from the crucible, lowered into a vessel with liquid nitrogen, and kept for 1 min until cooling. Then transferred to a glass bottle with a lid and put in a dry, closed desiccator. After remixing, the samples are pressed, heated to 980 ° C and incubated for 5 hours using thin tablets, and then incubated in liquid nitrogen for 1 min. After batching, the prepared powder sample is examined by physicochemical methods. According to x-ray phase, structural and chemical analyzes, the product is a complex lithium-lanthanum hafnate of the composition Li ₇ La _2.949996 Nd _0.05 Ho _0.00000026 Er _0.0000015 Dy _0.0000024 Hf ₂ O ₁₂ and has a tetragonal modification of the garnet structure with lattice parameters a = 13.0984 Å, c = 12.6292 Å , A = 2166.77 Å ³ . The average crystallite size according to scanning electron microscopy is ~ 2.4-3.2 μm. The radiation intensity when it is used as a luminescent material for converting exciting monochromatic laser radiation with a wavelength of 808 nm into a series of emission lines 2-2.3 μm, 2.5-2.9 μm, 3.1-3.35 μm short-wave (1-3 μm) IR range is shown in FIG. 2 (x = 0.05).

Example 2

As starting reagents take: 2.8164 g of HfO ₂ (analytical grade); 3.1605 g La ₂ O ₃ (chemically pure) (mixed with Nd ³⁺ , But ³⁺ , Er ³⁺ , Dy ³⁺ in an amount of 1.2⋅10 ^-3 , 2⋅10 ^-6 , 5⋅10 ^-5 , 1⋅10 ^-6 mass%) and 0.1126 g (Nd ₂ O ₃ ) (chemically pure) (mixed with La ³⁺ , But ³⁺ , Er ³⁺ , Dy ³⁺ in an amount of 8⋅10 ^-3 , 4⋅10 ^-4 , 5⋅10 ^-5 , 4.5⋅10 ^-3 wt.%), Preliminarily calcined at 850 ° С for 5 h, 1.9062 g Li ₂ CO ₃ (chemically pure) with an excess of lithium 7 % Next, the samples are intensively mixed, abraded in an agate mortar with the addition of a few drops of ethyl alcohol, and subjected to pressing under a pressure of 3000 kg / cm ² . As a result, 2 large tablets are prepared with a height of 10 mm and a diameter of 10 mm and two thin tablets with a height of 2.2-2.5 mm, which are necessary for laying on the bottom of the alundum crucible and on top of the main tableted sample. Next, the pressed sample is placed in an alundum crucible with a height of 35 mm and an inner diameter of 27 mm and then placed in the SNOL-E5SS furnace, heated to 900 ° C and held for 5.2 hours. The heating rate in this case is 35 deg / min. The tablet sample obtained after heat treatment is quickly removed from the furnace and from the crucible, lowered into a vessel with liquid nitrogen, kept for 2 minutes until cooling. Then transferred to a glass bottle with a lid and put in a dry, closed desiccator. After remixing, the samples are pressed, heated to 960 ° C and incubated for 5.2 hours using thin tablets and, in the same manner as described above, incubated in liquid nitrogen for 2 minutes. After batching, the prepared powder sample was examined by physicochemical methods.

According to X-ray phase, structural, and chemical analyzes, the product is a complex lithium-lanthanum hafnate of the composition Li ₇ La _2.899993 Nd _0.1 Ho _0.00000047 Er _0.0000015 Dy _0.0000047 Hf ₂ O ₁₂ and has a tetragonal modification of the garnet structure with lattice parameters a = 13.0966 Å, c = 12.6287 Å , A = 2166.09 Å ³ . The average crystallite size according to scanning electron microscopy is ~ 2.4-3.2 μm. The radiation intensity when it is used as a luminescent material for converting exciting monochromatic laser radiation with a wavelength of 808 nm into a series of emission lines of 2-2.3 μm, 2.5-2.9 μm, 3.1-3.35 μm of the short-wave (1-3 μm) IR range is shown in FIG. 2 (x = 0.1)

Example 3

As starting reagents take: 2.4091 g HfO ₂ (.h.p.a); 2.7734 g La ₂ O ₃ (chemically pure) (with an admixture of Nd ³⁺ , Ho ³⁺ , Er ³⁺ , Dy ³⁺ in an amount of 1.2310 ^-3 , 2⋅10 ^-6 , 5⋅10 ^-5 , 1⋅10 ^-6 mass%) and 0.02407 g (Nd ₂ O ₃ ) (chemically pure) (mixed with La ³⁺ , But ³⁺ , Er ³⁺ , Dy ³⁺ in an amount of 8⋅10 ^-3 , 4⋅10 ^-4 , 5⋅10 ^-5 , 4.5⋅10 ^-3 wt.%), Preliminarily calcined at 900 ° С for 4 h, 1.6306 g Li ₂ CO ₃ (chemically pure) with an excess of lithium 10 % Next, the samples are intensively mixed, abraded in an agate mortar with the addition of a few drops of ethyl alcohol, and subjected to pressing under a pressure of 3000 kg / cm ² . As a result, 2 large tablets are prepared with a height of 5 mm and a diameter of 10 mm and two thin tablets with a height of 2-2.3 mm, which are necessary for laying on the bottom of the alundum crucible and on top of the main tableted sample. Next, the pressed sample is placed in an alundum crucible with a height of 35 mm and an inner diameter of 27 mm and then placed in the SNOL-E5CC furnace, heated to 910 ° C and held for 5 hours. The heating rate is 30 deg / min. The tablet sample obtained after heat treatment is quickly removed from the furnace and from the crucible, lowered into a vessel with liquid nitrogen, and kept for 1 min until cooling. Then transferred to a glass bottle with a lid and put in a dry, closed desiccator. After remounting, the samples are pressed, heated to 980 ° C with a heating rate of 35 deg / min and incubated for 5 hours using thin tablets and, in the same manner as described above, incubated in liquid nitrogen for 1 min. After batching, the prepared powder sample was examined by physicochemical methods. According to x-ray phase, structural, and chemical analyzes, the product was a complex lithium-lanthanum hafnate of the composition Li ₇ La _2.974997 Nd _0.025 Ho _0.00000016 Er _0.0000015 Dy _0.0000012 Hf ₂ O ₁₂ and has a tetragonal modification of the garnet structure with lattice parameters a = 13.0992 Å, s = 12.6285 Å. , A = 2166.91 Å ³ . The average crystallite size according to scanning electron microscopy is ~ 2.4-3.2 μm. The radiation intensity when it is used as a luminescent material for converting exciting monochromatic laser radiation with a wavelength of 808 nm into a series of emission lines of 2-2.3 μm, 2.5-2.9 μm, 3.1-3.35 μm short-wave (1-3 μm) IR range is shown in FIG. 2 (x = 0.025)

Thus, the authors propose a new chemical compound, complex lithium-lanthanum hafnate with a garnet structure of a tetragonal modification of the composition Li ₇ La _3-xyzn Nd _x Ho _y Er _z Dy _n Hf ₂ O ₁₂ , where x = 2.5⋅10 ^-2 -1⋅10 ^-1 , y = 1.6⋅10 ^-7 -4.7⋅10 ^-7 , z = 1.5⋅10 ^-6 , n = 1.2⋅10 ^-6 -4.7⋅10 ^-6 , as a luminescent material for converting monochromatic laser radiation with a length 808 nm waves in a series of emission lines 2-2.3 microns, 2.5-2.9 microns, 3.1-3.35 microns, which can significantly expand the range of convertible radiation.

Claims (2)

1. Complex hafnate of lithium-lanthanum with the composition Li ₇ La _3-xyzn Nd _x Ho _y Er _z Dy _n Hf ₂ O ₁₂ , where x = 2.5⋅10 ^-2 -1⋅10 ^-1 , y = 1.6⋅10 ^-7 - 4.7⋅10 ^-7 , z = 1.5⋅10 ^-6 , n = 1.2⋅10 ^-6 -4.7⋅10 ^-6 , as a luminescent material for converting monochromatic laser radiation with a wavelength of 808 nm into a series of emission lines of 2-2.3 μm 2.5-2.9 μm; 3.1-3.35 μm. 2. A process for preparing a lithium lanthanum hafnate composition of Li ₇ La _{3-xyzn Nd x Ho y Er z} Dy n Hf ₂ O _12, where ^{x = 2.5⋅10 -2 -1⋅10 -1, y} = 1.6⋅10 - ⁷ -4.7⋅10 ^-7 , z = 1.5⋅10 ^-6 , n = 1.2⋅10 ^-6 -4.7⋅10 ^-6 , including obtaining the initial mixture of stoichiometric amounts of oxides of the corresponding metals, previously calcined at a temperature of 900-910 ° C, and lithium carbonate taken in excess of 7-10%, its intensive mixing and abrasion with the addition of ethyl alcohol, pressing, heating to a temperature of 900-910 ° C with a heating rate of 30-35 deg / min and holding at this temperature for 5- 5.2 hours, by then the resulting product is quickly removed and placed in liquid nitrogen with a holding time of 1-2 minutes, then it is kept in a dry atmosphere under normal conditions, after which the product is re-knitted, pressed, heated to a temperature of 960-980 ° C with a heating rate of 30-35 degrees / min, maintained at this temperature for 5-5.2 hours and again placed in liquid nitrogen with an exposure of 1-2 minutes.

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