The method of obtaining diamonds fancy red

 

(57) Abstract:

The invention relates to the field of processing (refining) of the diamond to give them a different color colouring and may find application in the jewelry industry. The method consists in the fact that in the crystal lattice of natural diamond type Ia containing defects And or natural high diamond type Ia, containing more than 800 ppm of nitrogen in the form of defects or B1, form isolated nitrogen atoms in positions of substitution - defects C. Natural diamond type Ia containing defects And annealed in high-pressure apparatus at a temperature of more S when stabilizing the pressure 6,0-7,0 Gpa, and then irradiated with electron beam 51015-51018cm-2when 2-4 MeV and are annealed in vacuum at a temperature of at least S. Natural high diamond type Ia, containing more than 800 ppm of nitrogen in the form of defects or B1, is irradiated with high-energy stream of electrons with a dose of more than 1019cm-2and are annealed in vacuum at a temperature of at least S. Get diamonds fancy red diamonds with a stable N-V color centers, absorbing in the wavelength range 400-640 nm.

Izopet the particular give natural diamonds unique fantasy red and can find application in the jewelry industry.

A method of obtaining diamonds red-yellow and black shades, based on the principle of color overlay, i.e., the desired color by mixing the sample natural color with “caused” by influencing the flow of electrons in the range of 51015-51018cm-2and annealing at 300-S over time from 30 min to several hours at atmospheric pressure and in an ultrahigh vacuum or with pulse heating. The process can be repeated many times to obtain a desired color (RU 2145365 C1, 10.02.2000).

Modern conventional physical classification of diamonds on the types described in a large amount of scientific literature (for example, John Walker Optical absorption and luminescence in diamond - Reports on Progress Physics, 1979, v.42) and divides the diamonds into four types:

- IIa - malvestiti diamonds. Basic classification criteria: the absence of absorption in the infrared region of the spectrum, a distinct region of fundamental absorption in the ultraviolet region of the spectrum at 225 nm. Diamonds of this type are quite rare, their content does not exceed 2% of the total weight of natural diamonds;

- IIb - blue semiconductor diamonds. Contain less nitrogen is a - an isolated atom in position substitution;

- Ia is the most common type of natural diamonds (up to 98%) containing 0.3 atomic percent nitrogen. The most common forms of occurrence of impurity nitrogen are defects And representing close nitric couple in the neighboring lattice sites, and defects B1, which are the four nitrogen atom around the vacancy;

- Ib is the most rare (less than 0.2%) of naturally occurring diamonds and make up the majority of synthetic diamonds. Contain isolated nitrogen atoms (defects) as impurity substitution in the amount of up to 0.05 atomic percent (about 5-6 ppm). The absorption band associated with the defects, begins in the visible region, about 500 nm, and increases toward shorter wavelengths, causing a yellow color diamonds are type Ib.

It is known that to obtain a diamond different shades of red among the variety of natural diamonds using optical spectroscopy methods produce crystals containing part of the impurity nitrogen in the form of isolated atoms substitution (defects). Physical classification of diamonds on the types of such crystals can be attributed either to a type Ib or mixed types Ia+Ib jinye the processes of transformation of defects in the crystal lattice of the diamond type Ib irradiated with a flux of high-energy electrons (1022m-2/2 MeV) and subsequent annealing in vacuum (800C, 2 h). In the irradiation process, a large number of primary radiation defects: vacancies and the interstitium. Subsequent high-temperature annealing in vacuum assures a robust N-V color centers, which represent isolated nitrogen atoms in positions of substitution with vacancies in neighboring lattice sites. Such defects have absorption in the red region of the spectrum at wavelengths less than 640 nm (1,945 eV) and cause different intensity of red color of the diamond crystals.

A method of obtaining purple diamond diamond synthetic diamond. (US 4950463 AND 21.08.1990). According to this method, the synthetic diamond of type Ib nitrogen in the form of defects in the range of 81017-1,41019at/cm3(or from 4.5 to 80 ppm) is irradiated with the electron flow in the range of 51016-21018cm-2when 2-4 MeV, followed by annealing in a vacuum of not less than 10-2Torr at a temperature of 800-C for more than 20 hours Get crystals purple diamond N-V color centers having absorption in the range 500-640 nm at the peak of 570 nm.

However, as determined from the analysis of the excitation spectra of luminesce is. the from.-Mat. of Sciences, Minsk, 1989, 21 C.), N-V centers absorb in the range of 400-640 nm. This absorption in diamonds are type Ib is superimposed on the absorption of defects With starting and growing at wavelengths less than 500 nm. In the end, the total absorption spectrum of the diamond type Ib N-V centers is in the range of wavelengths 400-640 nm.

The objective of the invention is to provide such a method of producing diamond fancy red color, which would allow in the crystal lattice of natural type Ia diamond to obtain a stable N-V color centers having absorption in the red region of the spectrum at wavelengths 400-640 nm.

To do this, use crystals of natural diamond type Ia and in its crystal lattice form isolated nitrogen atoms in positions of substitution of the defects, is irradiated with high-energy electron beam and is subjected to high temperature annealing in vacuum.

When this natural type Ia diamond contains an admixture of nitrogen in the form of defects or is high and contains an admixture of nitrogen in the form of defects or B1 with a concentration of more than 800 ppm.

Natural type Ia diamond containing an admixture of nitrogen in the form of defects And pre-put in the office of the high pressure high temperature is to obtain a high-energy stream of electrons 51015-51018cm-2, preferably 10 cm-2when 2-4 MeV and subjected to high temperature annealing in vacuum at a temperature of at least S.

Natural high diamond type Ia containing an admixture of nitrogen in the form of defects or B1 with a concentration of more than 800 ppm, treated with a high-energy stream of particles, such as electrons, with a radiation dose of more than 1019cm-2and subjected to high temperature annealing in vacuum at a temperature of at least S.

Our experimental data indicate that when NRNT-processing natural type Ia diamond containing an admixture of nitrogen in the form of defects And (pair of nitrogen in the neighboring lattice sites), at a temperature of more S is the dissociation approximately 15-20% of the defects And education, along with other defects defects in a concentration of not less than 10 ppm. As shown by previous studies, see Vince Century, (Change colors brown natural diamond under high pressures and temperatures. Notes of the Russian Mineralogical society, 2002, 4, pp. 112-119), at lower temperatures NRNT-processing (less S) dissociation of defects and consequently the formation of defects does not occur. Defects HT-treatment exposure to electron flow and high temperature annealing of diamond vacuum formed stable N-V color centers, having absorption in the red region of the spectrum at wavelengths 400-640 nm and providing diamond different shades of fantasy red.

The mechanism of appearance in the crystal lattice of diamond defects under irradiation of natural high diamond type Ia containing an admixture of nitrogen in the form of defects And (pair of nitrogen in the neighboring lattice sites) or B1 (four nitrogen atom around vacancies) with a concentration of more than 800 ppm, high doses of high-energy particles such as electrons, associated with the displacement of the nitrogen atoms forming part of the defects a and B1, mesosaline position. In the process subsequent to the irradiation of high-temperature annealing megaselia nitrogen atoms annihilate vacancies, forming isolated nitrogen atoms in positions of substitution, i.e., defects C. was Also observed absorption in a narrow strip 1346 cm-1caused by defects in C. That is, in the crystal lattice of the diamond along with interstitial nitrogen atoms appear isolated nitrogen atoms in positions of substitution - defects C. the Concentration of defects is about 5 ppm. Then formed in this way defects With capture vacancies, forming a stable N-V color centers having fantasing red.

All changes in the set and the concentration of optically active defects, such as a, B1, C, N3, N3 and N-V color centers in the crystal lattice of the diamond is determined by the intensity of the corresponding absorption bands in the infrared, visible and ultraviolet regions of the spectrum.

Examples of the method of obtaining diamonds fancy red color with a stable N-V color centers, absorbing in the wavelength range 400-640 nm.

Example 1.

Using a crystal of natural diamond weight of 1.84 carats, initially containing the impurity nitrogen in the form of defects And with a concentration of 92 ppm, and defects B1 concentration 258 ppm. In the spectra of infrared absorption was also observed band 1370 and 1430 cm-1due to the "platelets and narrow line 3107 cm-1due to hydrogen impurity defects. In the visible range of the spectrum at wavelengths less than 650 nm, was observed monotonic increase in absorption toward shorter wavelengths. Observed weak absorption at 415 nm and 503 nm, caused by defects N3 and N3. In view of the absorption spectra and the set of impurity defects of the crystal clearly corresponded to the type Ia diamonds. The diamond is subjected to NRNT-processing in high-pressure apparatus at a temperature of any defects B1 remained unchanged and was formed about 20 ppm defects C. The absorption intensity associated with the "platelike" decreased three times; absorption associated with impurity hydrogen was no longer observed. In the visible range of the spectrum was increased absorption at wavelengths less than 550 nm. The edge bandwidth was at 423 nm. The spectra were present system: 503 nm is very weak intensity and 990 nm in the near infrared region. Crystal color after NRNT-processing became greenish-yellow. Recruitment impurity defects of the crystal has already been determined as a diamond mixed Ia+Ib type.

Then the crystal is irradiated with electron energy of 3.0 MeV and a dose of 1018cm-2. The irradiation parameters such constructs in the crystal lattice of diamond is about 10 ppm of vacancies, which coincides with the data obtained on synthetic diamonds, see Vince Century, (color Change synthetic diamonds as a result of irradiation with fast electrons and subsequent annealing. Journal of Gemmology, 2002, 2(5), S. 19-33). The color of the crystal after irradiation was opaque dark green. Then the diamond is placed in a cold quartz ampoule, in which it is annealed for 24 hours at C. In the annealing process due to the migration of vacancies and their capture isolated nitrogen atoms in the crystal 640 nm, with a maximum at 570 nm was superimposed on the original (before irradiation with fast electrons and subsequent annealing) absorption edge bandwidth at 423 nm, which led to the final color crystal diamond, which was defined as an intense fantasy purple-red.

Example 2.

Using a crystal of natural diamond weight 2,948 carats, with defects And, with a concentration that did not allow to record the spectra of infrared absorption. From him saw off a piece of mass 0,236 carat, and this piece is made of two plane-parallel plate with a thickness of 0.2 and 0.3 mm Concentration of defects in both plates was about 800 ppm. In the infrared absorption spectra were observed in one system of the bands with the most intense band 1282 cm-1typical of type Ia diamonds containing defects A. the absorption Edge was in the ultraviolet region of the spectrum at 300 nm. Absorption in the visible range was absent. Both plates are irradiated by a flux of high-energy electrons (3.0 MeV, 1019cm-2). In the irradiation process records became completely black opaque color. After exposure the plate is annealed in evacuated quartz ampoule at a temperature of about C within 2 the color.

In the spectra of infrared absorption in addition to band-related defects And observed absorption band at 1450 cm-1which is associated with the manifestation in the spectra of single interstitial nitrogen atom that described for the crystal synthetic diamond (Malogolowkin Century, the Study of the impurity composition and the real structure of synthetic diamonds by spectroscopic methods. Abstract of thesis of K. F.-M. N., Kiev, IPM Academy of Sciences of USSR, 1979, 21 C.). It was also observed absorption in a narrow band 1346 cm-1caused by defects in C. That is, in the crystal lattice of the diamond along with interstitial nitrogen atoms appeared isolated nitrogen atoms in positions of substitution (the defects). The concentration of defects and amounted to about 5 ppm, and in the visible range of the spectrum appeared intensive system acquisitions 640 nm, indicating the formation of the N-V color centers.

After staining of both plates in red color similar technological procedures were done with the remaining large piece of diamond weight 2,712 carats. It also changed its color from the original transparent to intense fantasy purple-red.

Thus, the proposed method can find the use of the method can be processed (refined) all natural diamonds are type Ia, not containing in the initial state, the admixture of nitrogen in the form of defects, but in any concentration impurity nitrogen in the form of defects and/or B1.

The method of obtaining diamonds fancy red color with a stable N-V color centers, absorbing in the wavelength range 400-640 nm by irradiation of electron beam and annealing at a temperature of not less than C in a vacuum, characterized in that use natural diamond type Ia and in its crystal lattice form isolated nitrogen atoms in positions of substitution - the defects by high-temperature processing in high-pressure apparatus at a temperature of more S when stabilizing the pressure 6,0-7,0 Gpa carried out before irradiation high-energy stream of electrons with a dose of 51015-51018cm-2when 2-4 MeV when using diamond containing defects, or by irradiation vysokoenergeticheskom the flow of electrons with a dose of more than 1019cm-2when using high-nitrogen natural diamonds, containing more than 800 ppm of nitrogen in the form of defects or B1.

 

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