IE920846A1 - A process for the synthesis of diamond - Google Patents

Description

1. Field jof the invention This Invention relates to a process for the synthesis of transparent diaaord single crystal suitable for use as a aaterlal for decoration and optical particularly, It Is concerned with a process for the synthesis static high pressure and high teaperature, specifically high purity, nitrogen-free, colorless and transparent dianond of Ila type. 2. Descri >tion of the Prior Art At the pnsent tine, coaoerclally available diamond for decoration is Halted to natural dianond and In particular, colorless and tranparent dlaaond parts, and aorje of dianond at with little In ernal defects (Inclusions of foreign atneral crystals, etc.) is selected fr >«i those ntned In South Africa or Soviet and thus aarketed.

Natural decora: Is on sale In are IR anvil c having no abso Ive dlaoond has high property value and among jewels, dianond he largest aaounts. As an optical part using diamond, there ills, laser window materials, etc. and In any case, a dlaaond iptlon of nitrogen In the infrared range, called Ila type, ia selected from ratural gea stones and used. However, the mining aaount of colorless and transfarent gea stones Is very stall, thus resulting In problems on stable supply end price.

That is, natural dlaaond has the disadvantage that a transparent and stone Is ained In a snail aaount and Is thus expensive, output of a rough stone having no absorption of nitrogen in the is so little es represented by, for exoaple, an output of the lie type of 1-2 X based on the whole rough stones, thue resultcolorless rough Above all. the infrared range above described ing In a problem on supply thereof. In particular, a large-sized window aaterlal of 8 i Transparen several dlaaond n diameter la hardly available. and colorless dlaaond has first been synthesized in artificial anner in the ltoos. This synthesis was carried out by the teaperature gradient aethod using a Fe-3 -5 wt X Al alloy as a solvent netal, thus obtaining crystals with 0.7 ~l.O carat in the fora of brilliant. The -ifl resulting dlaiond was estlisted as 0 to K by the color scale of natural gem {GIA Standard standard of gem provided hy the American Ge® Institute)(US Patent No. 40''9980). However, such synthetic diamond bee not been marketed because the synthesizing cost is higher than the price of diamond as natural gem.

Artiflctf! diamond is ordinarily colord yellow because during synthesis et an ultra-hijgh pressure and high temperature, nitrogen in e solvent· Is taken In the crystal! lattice, but colorless and transparent diamond oan be obtained by adding a nitrogen getter to the solvent. As this nitrogen getter. Al is well known as llscloaed in, for example, The Journal of Physical Chemistry, Vol. 75, No. 11 (1971), p 1838. Specifically, US Patent No. 40343068 discloses that colorless talned by add! No. 39 (1984), Ti or Zr to a However, Φ Pe-Zr, φ ( diamond can be and transparent diamond single crystal of gea grade can be obig 3 to 5 X by weight of Al to a Pe solvent.

As an exaiiple of other nitrogen getters than Al, It has been reported in aMuki-zalshuts| Kenkyujo Hokoku deport of Inorganic Material Institute)*, page 16-19 that nitrogen In the crystal is removed by adding Solvent metal. qooblnatlons capable of producing colorless diamond are only e-Nl) alloy-Zr and φ (Nl-Mn) ailoy-Zr and no such colorless formed with other combinations, in the above described combinations of Φ to Φ, only the combination Φ of Fe-Zr is capable of giving one having no awdorption In a wavelength range of at most 500 nm. The presence of the abiorptlon In the wavelength range of at most 500 ns means that nitrogen atoms ire not completely removed.

Purtheraor t. It has already been reported by B.H. Strong and P.H. Cherenko In J- Chem. Phys. 78 P (1971) that in order to grow e colorless crystal without adding inch a nitrogen getter, the growth rate should be reduced to the case of growing a yellow crystal of lb type, ar, synthetic colorless and transparent diamond has not been at most 60 X of in part leu produced on a cqmmerclal scale, because of higher synthesis cost thereof than - J IE 920846 decorative diamond. The reason therefor is that not only an special apparatus is required for the synthesis of such diaIn order to obtain a good quality crystal, It ta required to the growth rate, since in the case of adding a nitrogen getter a solvent, the solvent Js taken or Included tn the crystal that of naturh expensive and ond, but alec largely lower such as Al to (this phenoaeron will hereinafter be referred to aa inclusion”) with the increase of the ferior crystal carbides such in the crystal When usln; solvent netal, transparent dihi aaount of the nitrogen getter added, thus resulting in an inWhen using Ti or Zr as a nitrogen getter, in particular. is TIC or ZrC, foroed in the solvent during synthesis, are taken and accordingly, It is difficult to obtain a complete crystal. Al as a nitrogen getter and unlforaly dissolving it in the it is found necessary in order to synthesize colorless and ond, according to the Inventors' experimental results, to add the nitrogen gutter in a proportion of at least 4 ϊ by weight (about 12 % by volune) to the 1 ng/hr so as solvent and in this case, the growth rate should be at least 0 effect the crystal growth without inclusion thereof. At this growth rate, hqnever, a synthesis tise of 200 hours or aore Js required, for example, for o talning a crystal of 1 carat (200 og), resulting In a large production cost.

When adding another nitrogen getter such as Ti or Zr having a larger retrogen than Al uniforsly to the solvent, a colorless and transfer be obtained even In an aaount of 2 % by voluoe and the largely be decreased, but large aeounts of carbides such as ncluded In the crystal and a good quality crystal can hardly activity with n parent crystal growth rata can TiC or ZrC are be obtained.

SUMMARY OF THE INVENTION It Is an object of the present invention to provide a process for the production of synthetic dlaaond, whereby the above described disadvantages and problems of the It is anot prior art can be solved. er object of the present Invention to provide a process for - J IE 920846 producing an irtlflclal synthetic diamond, which Is colorless and transparent and has no absorption of nitrogen in the infrared range, in economical and stable manner.

It Is a further object of the present Invention to provide artificial synthetic diamond which can be applied to deooratlve articles and optical articles.

It la a further object of the present Invention to a method for synthesiscrystal of Ila type, substantially free froa Impurities, at a static high pressure without lowering the growth rate, he. at a growth rate of about 2 tlaps of the prior art.

Ill further object of the present invention to provide a process jin artificial synthetic diamond, which Is colorless and transp tantlelly free from Inclusions, In economical and stable manner, lng a diamond It is a s for producing arent and subs whereby the abfve described problems of the prior art can be solved and use of synthetic diamond for decorative and optical appliances Is renthe artificial dered possible It is a s tll further object cf the present invention to provide a new process for thi production of a good quality diamond single Crystal which is colorless and i ransparent, and free from Inclusions by adding a nitrogen getter. These objects can be attained by a process for the synthesis of diamond, which comprises! aethod, using, getter for the froa the group 0.6 to 7 X by w only Al) to the , in the synthesis of diamond crystal by the temperature gradient las a solvent for the growth of the crystal, at least one metal selected froa tie group consisting of Fe, Co, Ml, Rn and Cr (nevertheless, at least two metals, are selected in the case of containing Fe) and as a nitrogen removal of nitrogen in the solvent, at least one metal selected insisting of Al, Tt, Ir, Hf, V, Nb and Ta in a proportion of ^Ight (nevertheless, at most 2 X by weight In the case of using solvent aetal.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are to Illustrate the merits end principle of the present Invention In detail. - 4 IE 920846 Fig. 1 If a cross-sectional view of an ultra-high pressure cell used for the synthesis of a single crystal in enbodinents of the present Invention.

Fig. 2 If a cross-sectional view of an ultra-high pressure cell used for the measurement of the diffusion rata of carbon In a solvent ln Experimental Examples.

Pig. 3 h a graph showing the relationship between the amount of Al and Its activity then an activity-increasing material Is added to a solvent netal.

Fig. 4 le a graph showing the relationship between the aaount of Al added to a solvent aetal and the amount of nitrogen contained ln diamond crystal.

Fig. 5 is a graph showing the relationship between the aaount of Λ1 added to a solvent ajtal and the aaount of a aetal Included In dlanond crystal.

Fig. 8 is a graph showing the relationship between the concentration of Al ln a solvent matal and the activity of Al.

Fig. 7 IS chamber.

Fig. 8 is a schenatie view of a construction of a sample In a synthesis a graph showing the relationship between the aaount of Al added to a solvent Utah as a nitrogen getter» and the aaount of nitrogen contained ln dlanond crystal In the prior art nethod.

Fig. 9 Is a graph showing the relationship between the amount of Al added to a so1vent ndtal and the aaount of the solvent netal In the crystal in the prior art aath Fig. 10 14 a schematic view of e reactor for practicing the present invention.

Fig. 11 Isl a schematic view of a construction of a sample chaaber ln one eabodlaent of tp»e present invention.

Pig. 12 ia a schematic view of a construction of a sanple chamber ln another embodiment of the present Invention.

DETAILED DESCRIPTION OF THE INVENTION The features of the present Invention can be summarized below: (a) Renova of Nitrogen V, Nb and Ta, (b) Prevep Contamlna by floating or Φ At lei: At least Jone ratal selected froa the group consisting of Pe, Co, Hl, Mn and Cr is used as a solvent for the synthesis of dlanond. In order to prevent I · a seed crystal* froa dissolving In the solvent. It Is preferable to previously add carbon wit 1 a nearly saturated concentration.

At least pne ratal selected froa the group consisting of Al, τι, Zr, Hf, epable of foralng nitrides In a solvent, Is added In the specified amount s(> as to reaove nitrogen causing coloration of a crystal in yellow. tlon of Contamination with Carbides, Oxides and Nitrides Ion of a crystal with carbides, oxides and nitrides is prevented precipitating according to the following two nethods: st one low viscosity element of Al, Sn. In, Ge, Ag, Cu. Cs, Pb, Sb end Zn Is aided to a solvent to prorate the rate of floating or precipitating of the abofe described carbides, etc. and the carbides, etc. are thus allowed to floit upward or precipitate downward before they are taken and Included. In the Crystal.

The addit the following on of the low viscosity elements Is generally carried out by bree methods: 1) An Inti rmetal 1 ic compound of a nitrogen getter element and low vlscoslty eleaent or fragaent in ia prepared and unlforaly dispersed In the fora of a powder the solvent.

II) A shedt of a nitrogen getter element and a sheet of a low viscosity element are stacked.

III) A nitrogen getter element and low viscosity eleaent in the form of Dys are mixed with or dissolved in the solvent. the nethod 1) Is more preferable. The additive amount of the •laments or al Above all. low viscosity eleaent la preferably 0.6 to 3 weight X based on the solvent. jgen getter ratal or an alloy thereof with e solvent ratal, i powder or fragoents, preferably having a diameter of 10 μ a Φ A nltr In the form of to l mm, la uniformly mixed with the solvent, in thia else range, even if the - a IE 920846 added metal isjcarburized, nitrided or oxidized, the floating or precipitating speed of the carbide, nitride or oxide la so large that these materials are not colloidal ind are floated or precipitated before Inclusion In the crystal. (c) Metho 1 of Making Crystal Colorless According to the prior art method, a micro amount of nitrogen cannot be removed end a irystal of G to B grade is only obtained. Thus, the present invention alms methods: Φ Since at further making colorless the crystal by the following two nitrogen gettei promote remove the residual nitrogen forms a deep energy level N-type semiconductor, at leait one of B, Ga, Be, In and LI Is added to the crystal to form AD pairs and elec rlcally neutralized. The additive amount thereof Is preferably In the range o 0.2 ppm to 2 weight X. Φ At lejst one of elements capable of increasing the acltlvlty of a , such as Pb, In, Cd and Bi. is added to form nitrides and to of nitrogen. (d) Synthesis of Good Quality Crystal Wien the above described nitrogen getter Is added, the diffusion rate and saturated concentration of carbon are lowered and carbon to be supplied Is lacking. Thus, non-grown areas on the surface of the crystal are enlarged and the solvent metal tends to be Included In the crystal. In order to prevent this phenooenon, at least one of Sn, P and P, capable of increasing the activity of car weight.

The first thesis of dlamo getter to a earn; of diamond crys lied In that a getter 18 added xwi, Is added, preferably In a proportion of 0.1 to 10 X by wnbodlment of the present invention is a process for the synid of Ha type, comprising adding a aaterlal to be a nitrogen lie In a synthesis chamber and subjecting the sample to growth :ai at a static high pressure and high temperature, cbaracterlaterlal capable of Increasing the activity of the nitrogen In a required quantity.

In this embodiment, in order to achieve the above described objects of - T IE 920846 the present liven tion, the aaount of Al to be added to a solvent Is decreased to such an extent that the prob lea does not arise that the solvent netal Itself tends to be lreluded In a crystal and a required aaount of a eaterIal capable the acitvlty of Al Is added ao as to Bake up for the decreased effect of reaorlng nitrogen and to give an effect aore than the decreased one to Al in the decreased aaount. a chart showing increase of the activity of ai in the case of petal and in tho oase of adding an activity-increasing aaterial etai. As the aaterial for increasing the acitivity of a * such as Al, there are used Pb, In. BI, Cd and the like and Pig. 3 (8 only a solvent to the solvent nitrogen gette the required auount thereof Is generally In the range of 0.3 to 4 weight X, loss than 0.3 weight X, the addition effect le little, while weight X, Inclusion of the solvent eetal Is Increased, a graph; showing the relationship between the aaount of.Al added dtal and the aaount of nitrogen contained in diaaond crystal, i itrogen contained in diaaond crystal is estiaated by a wave since tf it is If more than 4 Pig. 4 Is to a BOlvent ai The aaount of fora of ESR (Electron Spin Resonance). Froa Pig. 4, it Is apparent that the aaount of nitre of Al. When 2 to the solvent. gen contained In diaaond crystal la decreased with the increase weight X of Al is added, the resulting diaaond is colored light yellow, while the addition of up to 4 weight X of Al results in substantially colorless dlaacnd.

Fig. 5 is i graph showing the relationship between the aaount of Al added to a solvent aetal and the aaount of a netal included In diaaond crystal (content of solvent aetal). The content of the solvent aetal in the crystal is estimated by th>. use of a aagnetlc balance.

As Is evldipt from Fig. 5, the content of a solvent aetal Is increased with the Increase of Al. Nhen a crystal (lb type) Is grown without adding Al the content of the solvent aetal Is 0.2S to 0.50 X by weight, which is less tli$n when adding Al.

When a crystal of Ila type (geaetone), with a saall aaount of nitrogen, - I IE 920846 is applied to optica] aateriais, ultra-precision cutting tools, surgical knives, etc., It is required to prevent it fro· inclusion of metal impurities end to eliminate Included sites or vicinities thereof In the gemstone. Considering 7, the aetal content should preferably be reduced to at nost and to this end, addition of Al to a solvent aetal should be the product I vi 0.5 X by weigh suppressed to nt aost I X by weight.

The Inven and the aaount according to ti tration (weight Is shown in Fig ore have nade studies on the aechanlsa of reaovlng nitrogen by Al so as to f I Ad a method for effectively reaoving nitrogen froa a crystal by At In a decree!ed quantity, e.g. about 1 X by weight. Consequently, it Is found that an Equilibrium relationship exists between the aaount of Al added of nitrogen in the crystal and N ia reaoved as AIN, that is. β reaction of Al ♦ N -» AIN with high possibility. If nitrogen Is removed by (he reaction as described above, it Is considered effective to Increase the activity of Al as a method of forwarding thia reaction to the right without changing the absolute quantity of Al. That Is, this nethod is a trial of raiding only the activity without changing the absolute quanlty by adding a material capable of Increasing the activity of Al to the solvent.

For exemplja. the relationship between the activity of Al and the concenX) of Al in a solvent having a composition of Fe-40 X Co-1 X Al . 8. It Is apparent froa Fig. 6 that when 4 X by weight of Al la added, ths activity is 0.005, the crystal being substantially colorless but having large contents of impurities. Since the activity of Al is about jy weight of Al Is added (the orystal having less Impurities but ght yellow), it Is only necessary to add such a material that ty Is given as when 4 X by weight of At is added. There are sriala capable of raising the activity of Al, but above all, 0.001 when 1 X being colored 1 the same actlvl a number of mat Pb, In, Bi and 3d are preferably used. Xn Table 1 are shown, for example, activities of A which are calcu Properties of B when about 5 X by weight of Al is added to various elements, ated from the data of 'Selected Values of the Thermodynaaic nary Alloys; American Society For Metals*. - s IE 920846 Solvent Table Activity of 1 Solvent Activity of Element Al .Element Al Au 0.0008 In 0.727 Be 0.26 Ml 0.052 Bi 0.016 Nl 0.0000031 Cd 0.051 Pb 0.086 Cu 0.001 Si 0.473 Fe 0.01 Sn 0.473 Ga 0.113 V 0.14 Ge 0.028 Zn 0.184 Mien predaterained amounts of these materials are added to the solvent to tncrease th,t activity of Al, the reaction of forming AIN is accelerated, inclusion of n trogen In the crystal is decreased, even addition of l X by weight of Al r to this embodiment, in the synthesis of dlaaond at a static In particular, In the synthesis of high purity diamond of Ils lubstantlally free froa nitrogen and colorless and transparent, >Ie of Increasing the activity of Al, as a nitrogen getter, is nitrogen is effectively reeoved by such a small amount of Al According high pressure, type, which is a aaterJal cape added and thus, that bad influe ices due to the addition of Al, e.g. inclusion of the metal do not appear, diamond of Ila Therefore, according to the process of the present invention, ype can be synthesised at a growth rate of about 2 times as higher as in tbi.prior art.

In the sec, nd embodiment of the present Invention, there la provided a - 1 0 to add Al to a Al added to th< gen content) h added to the s< process for th< synthesis of dtaaond of Ila type, which coeprisee floating upward or precipitating downward nitrides, carbides or oxides forned by addition of a nitre gen getter to reoove nitrogen.

In the prior art vethod, as described above, it has oalnly been eaployed solvent, in this case, the relationship between the aaount of solvent and the concentration of nitrogen in a crystal (nitroShown in Fig. 8 and the relationship between the amount of Al lvent and the amount of Inclusions (solvent oetal content, Included quantity) Is shewn In Fig. 9. However, there arises the following probleas: Φ When the additive aaount of Al is Increased, the nitrogen concentration Is decreased, but the Inclusion is increased.

For the synthesis of a good quality single crystal with less Inclusion. the growth rate Bust be lowered.

Excessive rest) val of nitrogen results In coloration of a crystal in blue due to sli jhtly retained boron (B) in the solvent.

On the ot her hand, whep sone eleaents functioning as a nitrogen getter but forning the corresponding carbides, etc. are added, the thus formed carhldea, etc. are included In the crystal and a good quality crystal Is hardly obtained.

In order t> solve the above described probless, the following Beans are eaployed In this eabodiaent: Φ At least one element selected from the group consisting of Tl, Zr, Hf, V, Nb and Ta Is chosen and added to a solvent as a nitrogen getter. These eleI Bents tend to f »im borides and thus have an effect of removing blue. Φ In ordsr to psevent.the carbides, etc. fro· being Included in the crystal, a low rtscostHy element such as Al, Sn, In, Ga, Ag, Cu, Gs, Pb, Sb and Zn is added Individually:or in coabination to increase the floating or precipitating rijte of the carbides, etc. and the carbides, etc. are allowed to float upward or precipitate downward before they are included in tbe crystal. -11IE 920846 (1) Actions of τι, zr. Hf, V, Mb and Ta as nitrogen getter I These eleients. individually or in coablnatlon, for· stable nitrides end function as a rltrogen getter. During the ease tine, when one of these elenents (e designated as A, nitrogen Is reeoved by the following reaction formula: A ♦ M -* AM (Kt reaction constant) (Ti) (M) (TIM) OrdinarlljL Pe, Co, Nl, Mn or Cr has been used as a solvent for the synthesis of diamond. In the above described reaction foraula, the effect of renovirg nltrogeri is larger when the reaction constant is larger. The reaction constant K, dejending on the variety of a solvent eleaent, is larger in a Pe solvent, but si Is carried out suer in s MI solvent. Therefore, «hen synthesis of diaaond In a Pe solvent, nitrogen can readily be reaoved, but in the ease solvent, the dlffulosn rate of carbon is so low that short supply of carbon tends to a higher growth take place and no good quality crystal cannot be obtained at rate. On the other hand, a solvent capable of giving a high Is taken In the carbon diffusion rate Is Co, so an alloy solvent of Pe and Co is preferably used for obtaining < good quality crystal.

A saall aiount of boron (e.g. several ppa) ts ordinarily contained in the above described solvent netal and about 1/10 of the solvent concentration crystal to give a concentration of 0. l to 0.0 ppn. If the nltrogen-removlhg effect of a nitrogen getter is excessive! jy large, the nitro gen electrically coapensated with boron in the solvent Is not contained in the crystal and conversion of froa transparent to bluelsh takes place.

Ti, Zr, Hft V, Mb and Ta tend to fora borides and thus function as a reduce blue color. (2) Effectb of Adding Low Viscosity Netal Eleaents such as Al, Sn, etc. TI. Zr, Hf, V, Mb and Ta fora stable nitrides and thus function as an effective getter for reaoving nitrogen in the solvent. However, these Betels boron getter to -11IE 920846 ainultaneously'react with carbon and oxygen dissolved In the solvent to fora I carbides and oAldes in large aoounts. The carbides, nitrides and oxides are Included In th< crystal to degrade the quality of the crystal. The carbides, nitrides and aides act as nuclei so that the solvent netal tends to be Included In the crystal. Accordingly, It la en important problea to reoove the carbides, nitrides and oxides before growth of the crystal. Since the getter elenent, carbo!, nitrogen and oxygen are unlforaly dispersed In the solvent, the resulting tarbldes, nitrides and oxides are In the for· of fine grains. These fine carbides, nitrides and oxides are not floated nor precipitated In a short tine even if there is a density difference fro· that of the solvent.

For the purpose of floating upward or precipitating downward the carbides, nitrides and aides In a short tine and not suspending the· during crystal growth, It Is nffecttve to lower the viscosity of the solvent.

Gnerally, the settling (floating) rate of colloidal and spherical fine grains are represented by the following foreula: r1 U = - - ( P - ί I ) I 9 u: settling (floating) rate r: radius of grain v : viscosity of solvent » : density of grain . : density of solvent g: : gravitational acceleration Therefore) the settling (or floating) rate of the solvent Is theoretically lowered In lnvorse proportion to the viscosity of the solvent so in order to Increase the Bottling (floating) rate, it la effective to lower the viscosity of the solvent -ISIE 920846 The aoounjt 3 X by weight, If more than 3 the rate of cr Addition of an Interact aetal, whereby As the in Intermetallic Sn-Zr type int Sn-V type Inte aetal11c compo and Sn-Ta type Sn«TI« is aore ation Itself ot is decoaposed diffused In a In considerably Another » nitrogen getter 11. According single crystal, vicinity of a creased, nltrog of a nitrogen the low vlscosl tratIon of cartel elusion of the ZrC in the cry e colorless, t io of the netal added to lower the viscosity la generally 0.5 to since If less than 0.5 X by weight, Its effect Is little, while X by weight, Inclusion of the solvent natal is Increased and rstal growth (s lowered. a low viscosity netal la preferably carried out by the use tlllc compound of the low viscosity netal with a nitrogen getter no carbide is forned and a good quality crystal can be obtained, eraetallic coapound, for exaaple, there are used Sn-TJ type compounds such as SntTh, Sn»TIi, SnTl, SnTl» and the like, (metallic coapounds such as SnZr, Sn«Zr, SnZr, and the like, ^metallic coapounds such as SnV» and the like, Sn-Nb type intersuch as SnNb and the like, Sn-Bf type interaetalllc coapounds internets] 1 ic conpounda. In particular, addition of SnTl· or effective. In this case. TIC does not exist isolated and foraT1C hardly takes place. Even lf a Sn-TI Interaetalllc coapound fora TIC. Sn exists near Tl and accordingly, TIC is readily sjalvent. Consequently, a good quality crystal can be obtained easy Banner. ejthod of adding a low viscosity coapound coup rises stacking a aetal sheet and a low viscosity aetal sheet, as shown in Fig. to this eabodlaent of a process for the synthesis of diamond a nitrogen getter is added or disposed to a solvent ln the crystal, so that the nitrogen reaoval efficiency Is lnrn is sufficiently removed even by addition of a saall amount g itter and inclusion of lapurlties hardly takes place. Since y aetal Is disposed on the seed crystal, Moreover, the concenn just before incorporated tn the crystal Is Increased, Insolvent oan bo provonted end tn addition, rewlnlng of TIC or can also be prevented. Thus, It le possible to synthesize rinsparent and Inclusion-free diamond crystal at a high growth a led rate.

As a meth xl of increasing the floating or precipitating rate of the carhides, etc., tie grain disaster of e nitrogen getter aetal Is Increased and uniformly disposed. In the foregoing formula, the floating rate la proportional to the iquare of the grain dlaaeter. If the grain diameter is smaller than 10 it in this case, the floating rate of the carbides, ate. is so saall that the carbides, etc. are Included In the crystal, while If larger than 1 mm, the reaction of the nitrogen getter with nitrogen Is decreased so that funnitrogen getter Is lowered. , etc. are elements tending to form nitrides. Accordingly, removed by adding these elements. In this case, further addiBf, etc. results in less inclusion of the solvent than when metals ot Al, In, Ca, oto. When Al alene Is added u a nllroctloning as thu Al, In, G A method ahd apparatus for synthesizing diamond single crystal by the temperature gredleit method using a seed diamond are described in (IS Patent No. at I on and drawings. The outline thereof will be illustrated for the practice of the present invention.

As shown 11 Pig. 10, within a pyrophllllte cylinder 3 there is concen>ned a graphite tube heater 2, within which there are disposed and a diamond seed S. On the diamond seed 5 are located a and further m carbon source 7, the lower part and upper part led with plugs 4 and 8. The plugs 4 aknd 8 and the pyrophllllte trlcally posit a pyrophllllte solvent aetal 6 of which are fl cylinder 8 are pressure media made acoording to a same standard.

Diamond Is synthesized by compressing the above described reaction vessel -isIE 920846 arranged In a liollow of a die consisting of cemented carbide at a predetermined pressure using the die consisting of cemented carbide and a pair of punches located above During the saae tine, the coomonly used pressure and teeperature are 5.8 to 5.6 GPa and 1260 to 1410 T.

In the third eabodlaert of the present invention, there is provided a process for th< synthesis of dlaaond single crystal by the teeperature gradient Bet hod, wt lch comprises using a solvent aetal to whioh an Al-X type Intermetallic conpoirid wherein X Is an element selected from the group consisting of Ti, Zr, Hf, In this ei various studies that when Al is high reactivity V, Nb and Ta is added as a nitrogen getter, bodlaent, the solvent aetal preferably consists of at least one meaeber selected froa the group consisting of Pe, Co, Ni, Nn and Cr, aore preferably contairLng 0.1 to 6.0 weight x of carbon. The aaount of the Al-X type intermetallic compound wherein X is an element selected from the group consistHf, V, Nb and Ta, added as a nitrogen getter, is preferably 0.l to 5 weight X tased on the solvent aetal.

In order ηο solve the above described probieas, the inventors have nade on nitrogen getters to be added and consequently, have found added to a solvent and simultaneously, an eleaent having a With nitrogen such as Ti, Zr, Hf, etc. is added thereto, the removal efficiency of nitrogen Is increased and Inclusion of carbides, etc. formed tn the solvent during the synthesis in the crystal is decreased, thereby obtaining a good quality diamond crystal of Ila type even at a relatively high growth rate.

As a resullt of further studies, it is found that when an intermetallic compound of Al ind Ti Is used as a nitrogen getter, the reaoval efficiency of nitrogen is firther increased and formation of carbides, etc. such as TIC is largely suppressed to considerably decrease the Inclusion thereof* Thus, it is confirmed that a good quality Ila crystal can be obtained even at a growth rate of about two times higher than that of the prior art and the present invention Is thus accomplished.

Fig. 12 ip a schematic view of a construction of a sample chamber for the crystal in an embodiment of the present invention, in which a , solvent metal 2, seed crystal 3, insulator 4, graphite heater sodium β are arranged, the solvent aetal containing a previously synthesis of a carbon source 6 and pressure added powder o selected from an Al-X type intermetallic compound wherein X is an element he group consisting of Ti, Zr, Hf, V, Kb and Ta.

Examples if the intermetallic comound are Al-Tl intermetallic comounds such as AlTi, ,liTl, A1«TI, AlTi. and the like; Al-Zr Intermetallic comounds such as AlZr, (L»Zr, Al»Zr, Al.Zr», AL»Zri, AliZri, AlZr,, AlZr, and the like; Al-Hf intermeti lllc comounds such as AlHf, ALiRf, Al.Hf, AI,Qf,. AL»Hf<, like. In addition, various Intermetallic comounds of Al-V, Alin» and Al-Ta tjlpes can be used.

These Intermetallic comounds are preferably used in an amount of as small t generally in an amount of 0.1 to 6 weight X, since if less x, removal of nitrogen cannot sufficiently be carried out and as possible, bu than 0.1 weight the resultant crystal considerably colors yellowish, while If more than 5 Inclusions are taken In the crystal, metal 2 shown in Fig. 12 is a metal consisting of at least weight X, more The solven one member sele:ted from the group consisting of Fe, Co, HI. Nn end Cr and In order to prerent the seed crystal from dissolution, 0.1 to 6-0 weight X of carbon is previously added. Wien using a solvent having a carbon content of less than 0.1 woight X or containing no carbon, it Is required to dispose a seed crystal dissolution preventing agent such as Ft on the seed crystal, but the arrangement of the seed crystal dissolution preventing agent causes polycrystall 1 mat Ion or Inclusion. This Is not preferable. If the carbon content -ITIE 920846 tertals in the exceeds 6 weight X, spontaneous nucleation tends to occur and crystal growth takes place at' other sites than the seed crystal, whereby crystals interferes with each other and no good quality crystal can be obtained. j As the seed crystal and carbon source, there can be used any of known aaart. The synthesis conditions by the teaperature gradient aethod can sul ;ably be chosen. Specific examples are given In the following Examples. to the process for the synthesis of dlaaond (n this eabodlaent, an Al-Z type Intermetallic compound wherein Z is an element selected from the group consisting of Ti, Zr. Hf, V, Nb and Ta is added as a nitrogen getter to Consequently, a good quality dlaaond crystal of Ha type can be obtained βνέη at a considerably larger growth rate than In the prior art. The reasons th When us ini of addition, e only Al es a nitrogen getter as described above, a large aaount g. 4 weight X or aore is required to synthesize colorless and transparent dlinond crystal. Accordingly, Inclusions tend to be taken in the crystal and the a good quality getter, even in parent crystal and even If the carbides, etc. growth rate should be decreased to at most 1 ag/hr to obtain crystal. On the other hand, when adding only Tl as a nitrogen a very small aaount of addition thereof, a colorless and translan be obtained, but TIC in a large aaount Is formed in a solvent growth rate of the crystal Is largely lowered, Inclusion of s Increased and a good quality crystal Is hardly obtained.

However, itch Inclusion can be suppressed to some extent by adding Ti as a nitrogen gettir and simultaneously adding Al of low viscosity, forming no carbide, to diffuse the formed TIC throughout the solvent metal.

Furthermore, when as in this eabodlaent, an interaetallic coround consist, e.g. A1T1, AhTi, AlTh, etc. is added, foraatlon of TiC is there Ib no isolated Tl and even If It is decomposed to form ing of Al and T decreased since TIC, TIC ia rea< Ily diffused in the solvent because of the presence of Al in -ilIE 920846 the vicinity of TIC. Consequently, a good quality, inclusion-free crystal can readily be obtlined and moreover, the removal efficiency of nitrogen Is substantially similar to in the case of Tl, reaching such an extent that nitrogen la substantial y removed even by addition of a very small amount, e.g. about 1 weight x. As described above, it la possible to synthesize a good quality.

Inclusion-free considerably h and colorless and transparent diamond crystal of Ila type at a gher rato by the use of an Intermetallic Oomound of Al-TI type as a nitrogen getter than when using Al and Ti Individually or in combination. Specifically, (hen 1 weight X of an intermetallic coaound of Al-Tl is added to the solvent metal, a colorless and transparent diamond crystal of Ila type can be obtain» even at a growth rate of 2.6 mg/hr.

In the fourth embodlaent of the present invention, there Is provided a process for thu synthesis of diamond single crystal by the temperature gradient method, wl Ich comprises using a solvent metal to which an Sn-X type intermetallic compoind wherein X is an element selected from the group consisting of Tl, Zr. Hf, V, Kb and Ta is added as a nitrogen getter.

In this eibodlaent, the solvent metal preferably consists of at least one nemeber selected from the group consisting of Fe, Co, Nt, Mn and Cr, more preferably contalring 0.1 to 6.0 weight X of carbon. The aaount of the Sn-X type intermetallic compound wherein X Is an element selected from the group consisting of Tl, Zr, Sf, V, Hb and Ta, added as a nitrogen getter, is preferably 0. l to 10 weight x Msed on the solvent metal.

In order ta solve the above described problems, the Inventors have made various studies and consequently, have found that when Sn is added to a solvent, the carbon potential In the solvent is Increased and non-growing parts on the surface of a graving crystal are decreased so that Inclusion in the crystal is somewhat suppressed. when an element having a tendency of foraing Its carbide, such a; TI, Zr, Hf, etc. Is added aa a nitrogen getter, and during the same time, Sn 11 added, carbides formed in the solvent, such as TIC and ZrC are almost diffused In the solvent and floated thereon before taken In the -isIE 920846 crystal and accordingly, a good quality diamond crystal of Ha type can be obtained even at a relativley high growth rate.

As a result of further studies, It ia found that when an lnteraetallic ind Ti or Zr la used as · nitrogen getter, the reaoval efficiency further Increased and foraatlon of carbides, etc. such as TIC compound of Sn of nitrogen Is synthesis of a carbon source 5 and pressure added powder of such as Sn«Tl·, la largely suppressed. Thus, it la confirmed that e good quality Ha crystal can be obtained even at a growth rate of about two times higher than that of the prior art and the present Invention is thus accomplished.

Pig. 12 la a schematic view of a construction of a saaple chamber for the crystal in an· eabodlaent of the present invention, in which a , solvent aetal 2, seed crystal 8, Insulator 4, graphite beater nedium 6 are arranged, the solvent metal containing a previously an Sn-X type intermetallic compound wherein X Is an eleaent selected froa the group consisting of Ti. Zr, Bf, V, Mb end Ta.

Exaaples qf the lnteraetallic coaound are Sn-Ti lnteraetallic coAounds Sn«Tl*, SnTli, SnTI» and the like; Sn-Zr lnteraetallic comounds such as SnZr, Sjn»Zr, SnZr, and the like; Sn-V intermetallic cooounds such as SnVi and the like; and Sn-Nb Intermetallic comound such as SnNb» and the like. In addition, various Intermetallic comounds of Sn-Hf and Sn-Ta types can be used.

These Inti rmetal lie comounds are preferably used in an amount of as saall os possible, bit generally In an aaount of 0.1 to 10 weight X, since If less than 0.1 weight X, removal of nitrogen cannot sufficiently be carried out and the resultant crystal considerably colors yellowish, while (f more than 10 •weight X, more inclusions are taken In the crystal.

The solver t metal 2 shown in Fig. 12 is e metal consisting of at least one member selected from the group consisting of Fe> Co. Mt, Rn and Cr and in order to prevent the seed crystal from dissolution, 0.1 to 6.0 weight X of carbon Is previously added. When using a solvent having a carbon content of less than 0.1 «eight X or containing no carbon, it Is required to dispose a -soIE 920846 seed crystal d ssolutlon preventing agent such as Pt on the seed crystal, but the arrengemen: of the seed crystal dissolution preventing agent oauscs polycrystalllzatloi or Inclusion. This Is not preferable. If the carbon content exceeds 6 weigjit X, spontaneous nucleation tends to occur and crystal growth other sites than the seed crystal, whereby crystals interferes with each othei and no good quality crystal can be obtained.

As the sefd crystal and carbon source, there can be used any of known maert. The synthesis conditions by the temperature gradient ably ba chosen. Specific examples are given In the following terlals In the method can sut Examples.

According Whert uslnj small amount ol obtained becaw la formed In a to the process for the synthesis of diamond In this embodiment, an Sn-X type Intermetallic oospound wherein X Is an element selected from the group conststlig of Tl, Zr, Bf, V, Kb and Ta Is added as a nitrogen getter and as an inclusion Inhibitor to a solvent netal. Consequently, a good quality of IIa: type can be obtained even at a considerably larger growth rate tlun In the prior art. The reasons therefor will specifically be explained as tq Sn-TI Intermetallic comounds: only Tl as a nitrogen getter as described above, even in a very addition thereof, a colorless and transparent crystal can be de of its high reactivity with nitrogen, but Tic In a large amount I solvent and even If the growth rate of the crystal Is largely lowered, inclusion of carbides, etc. la Increased and a good quality crystal Is hardly obtained..

However, such inclusion can be suppressed to some extent by adding Tl as a nitrogen getter and simultaneously adding Sn of low viscosity, forming no carbide, to diffuse the formed TIC throughout the solvent aetsl. When Sn is added to a solvent, the carbon potential In the solvent is Increased and nonembeded materials on the surface of a growing crystal are decreased so that inclusion In thb crystal Is somewhat suppressed.

Furthermore when as In this embodiment, an intermetallic comound consist* ing of Sn and:Tl, e.g. SnTi», SruTl». etc., is added, foraation of TIC is I decreased stncje there is no isolated Ti and even If the Sn-Ti interaetallic compound is decomposed to fori TIC, TIC is readily diffused in the solvent because of the iresence of Sn In the vicinity of TIC. Consequently, a good quality crystal cin readily be obtained and aoreover, the reaoval efficiency of nitrogen is sibstanttally slailar to in the case of Ti. reaching such an extent that nitrogen e.g. about 1 Is substantially reaoved even by addition of a very snail aaount, weight X. As described above, it Is possible to synthesize a good quality, Inclusion-free and colorless and transparent diaaond crystal of Ils type at a higher rate by the use of an interaetallic cooound of Sn-Tl type as a nitrogen getter than when using other nitrogen getters, a. g. Al or TI. Speclfically, when solvent metal, seed crystal s contacted with using the thus , weight X of an Interaetallic cooound of 8η>ΤΙ· is added to the a colorless and transparent diaaond crystal of Ila type can be obtained even it a growth rate of 2.5 ag/hr.

In the ft’th embodiment of the present Invention, there Is provided s process for tho synthesis of dlanond crystal by the temperature gradient method, which comprise: arranging a solvent aetal to be contacted with a carbon source, arranging at hast one metal slelected from the group consisting of Ti, Zr and Hf as a nltrogm getter at the solvent metal side between the solvent metal and a seed cry! tat disposed below the solvent aetsl and arranging At at the da between then In such a Banner that the seed crystal is not the nitrogen getter, and then starting synthesis of diaaond arranged assembly.

In this esbodiment, the solvent metal preferably consists of at least one eeeber selected froa the group consisting of Ft. Co, Ni, Hn and Cr, more preferably containing 0.1 to 6.0 weight X of carbon. The aaount of at least one aetal selected froa the group consisting of Tl, Zr and Rf. added as a nitrogen getter, is preferably 0.2 to 5 voluae X based on the solvent metal and the amount of Al ad led la preferably 0.1 to 2 voluae X based on the solvent metal. o synthesize a colorless and Inclusion-free diamond crystal In order at a higher griwth rate by adding a nitrogen getter, the following method Is employed In th s embodiment of the present Invention.

That is t< say, the inclusion tends to be readily taken in the crystal with Increase if the amount of the nitrogen getter and accordingly, it le desired to adjus' the amount of the nitrogen getter to as smaller as possible.

To this end, T: , Zr or Hf having e higher reactivity with nitrogen is used as a main ni tri gen getter end arranged only near the seed crystal.

Since the metal as the main nitrogen getter tends to react with carbon to fora Its carblie and causes to be taken in as Inclusions, low viscosity Al forming no carbide is disposed hetveen the above described nitrogen getter and I seed crystal fir the purpose of suppressing growth of the carbide and diffusing the carbide in a solvent before taken in the crystal.

Pig. 11 U a schematic view of a construction of a sample chamber for the synthesis of s orystal in one embodiment of the present invention, in which a sheet 3 consisting of Tl, Zr or Bf as a main nitrogen getter is disposed at the solvent she between a solvent metal Z and a seed crystal 6 and an Al sheet 4 Is disposed it the seed crystal side between them. The.nitrogen getter sheet 3 can be composed of Tl, Zr and Hf sheets, individual ly or in coablnation, for ted sheets of e Tl sheet and Zr sheet or alloy sheet of Tl-Zr. vent aetel 2, there is used at least one member selected from example, lamini as the sol the group consisting of Pe, Co, Nt, Rn end Cr and in order to prevent the seed crystal 5 added. When ui from dissolution, o.l to 0.6 X by weight of carbon Is previously Ing e solvent aetel having a carbon content of less than 0.1 X by weight or cdntalnlng no carbon, it is required to dispose a seed crystal dissolution preventing agent such as Pt on the seed orystal and the effect of the construction of the present Invention Is not sufficient.

If the carbon cbntent exceeds 6 weight X, spontaneous nucleation tends to occur end crystal growth takes place at other sites than the seed crystal, whereby crystals Interfere with each other and good quality crystal cannot be -H der growth of ore then 2.0 In this e According Tl, Zr or Hf w obtained.

In this cabodlaent, it is desired that the anount of Al to be added la adjusted to as aoall as possible, but It la generally In the range of 0.1 to 2.0 volune X to the solvent, since If less than 0.1 volume X. a layer of carbide of Tl, etc. arranged 4s a nitrogen getter la foried on the seed crystal to hlnthe crystal and the carbide remains nore In the crystal, while If volume X. more Inclusions are taken In the crystal, ibodlment, the anount of Tl, Zr or Hf to be added as a nitrogen getter Is preferably 02 to 5 volune X to the solvent, since If less than 0.2 volune X, nitrjgen Is not sufficiently renewed and the crystal colors yellowish, while If »ore than 8 volune X, Inclusions are Increased in the orystal.

As the se$d crystal and carbon source, there can be used any of known materials in the art. The synthesis conditions by the tenperature gradient method can sui ably be chosen. Specific examples are given In the following Examples. to the process for the synthesis of diamond in this embodiment, th high.reactivity with nitrogen Is used as 1 main nitrogen getter and disposed only In the vicinity of the seed crystal, so that the nitrogen removd efficiency Is high, and nitrogen is sufficiently removed even by addition of a considerably small amount thereof, whereby inclusions are decreased.

Furthermode, Al Is arranged on the seed crystal so that Tl, Zr or Hf is not contacted with the seed crystal and accordingly, the carbide such as TIC or ZrC is prevented from remaining In the crystal. Thus, colorless and transparent, Inclusl>n-free diamond crystal can be synthesized at a high growth rate.

In the six process for the which comprises ;h esbodloent of the present invention, there is provided a synthesis of diamond crystal by the temperature gradient eethod, arranging a solvent metal to be contacted with a carbon source, arranging at lei$t one metal slelected from the group consisting of Al, Ti, Zr - 3 4 IE 920846 and Bf as a nitrogen getter at the solvent aetal aide between the solvent metal and a seed crystal disposed below the solvent metal and arranging Sn at the seed crystal s contacted with using the thus de between the· In such a manner that the seed crystal is not the nitrogen getter, and then starting synthesis of diamond arranged assembly.

In this embodiment, the solvent metel preferably consists of at least one memeber select)d from the group consisting of Pe, Co. Nl, Hn and Cr, more preferably containing 0.1 to 6.0 weight X of carbon. The amount of at least one from the group consisting of Al. Tl, Zr and Hf, added as a , ia preferably 0.2 to 10 volume X based on the solvent metal of Sn added Is preferably 0.1 to 5 volume x based on the solvent metal selected nitrogen gette and the amount metal.

In order synthesize a colorless and Inclusion-free diamond crystal at a higher growth rate by adding a nitrogen getter, the following method is employed In th s embodiment of the present Invention.

That Is tl say, the luClualun tends to be readily taken in tbe crystal with increase Qf the amount of the nitrogen getter and accordingly, it is dethe amount of the nitrogen getter to as smaller as possible, nitrogen getter is arranged only near the seed crystal. sired to adjus1 To this end, a If there i re non-embeded materials on the surface of the crystal during growth thereof, the Inclusion is taken therein. In order to prevent this, Sn having a function of increasing the carbon potential is disposed between the above described nitrogen getter and seed crystal. When using Tl or Zr capable of readily fording its carbide as a nitrogen getter, the formed carbide causes to hinder growth of the crystal and to be taken in as the inclusion. Sn is Capable of suppressing growth of the carbide or diffusing the formed carbide in the solvent before being taken In the crystal.

Pig. 11 Is! a schematic view of a construction of a sample chamber for the synthesis of a srystal in one embodiment of the present invention, in which • nitrogen gettsr 6 (sheet-shaped in Pig. 11) consisting of Al, Ti, zr or Hf -15IE 920846 Is disposed at’ the solvent side between solvent octal 2 and a seed crystal 5 and Sn 4 (sheat-shaped in Pig. 11) Is disposed at the seed crystal side between then. The nitrogen getter 3 can be composed ot Al, Ti, Zr and Bf, individually or In coabination, for exeaple, laafnated sheets of an Al sheet and TI sheet or t TI sheet and Zr sheet, and alloy sheets of Al-Tl slloy or Tl-Zr alloy· i deslgnates a car >on source As the so the group cons seed crystal 5 vent ratal 2, there Is used at least one eember selected from Sting of Pe, Co. Ml, Mn and Cr and In order to prevent the fro· dissolution, 0.1 to 0.6 X by weight of carbon is previously added. When uiing a solvent aetel having a carbon content of less than 0.1 X by weight or curtaining no carbon, it is required to dispose a seed crystal dissolution pruventlng agent such as Pt on the seed crystal and the effect of Sn according to the construction of the present invention is not sufficient.

If the carbon In this «4bodlaent, it is desired that the amount of Sn to be added the range of 0.1 to 5 voluae X to the solvent, since if less x, there is little effect of preventing inclusions and when as a nitrogen getter, a layer of carbide such as TIC, etc. is generally if than 0.1 voIuk using Tt or Zr ie forned on the seed crystal to hinder growth of the crystal and the carbide renains lore lr or spontaneous the crystal, while if sore than S voluae X, polycrystalIlzatlon nucleation tends to occur.

In this eaudlaent, the anount of Al, Ti, Zr or Mf to be added as a nitrogen getter is preferably 0.2 to 10 volune X to the solvent, since If less than 0.2 volune X, nitrogen is not sufficiently reaoved and the crystal colors yellowish, while II rare than 10 voluae X. Inclusions are increased in the crystal.

As the see l crystal and carbon source, there can be used any of known materials In the irt. The synthesis conditions by the tenperature gradient aethod -21IE 920846 can suitably te ohosen. Specific exaaples are given in the following Examples.

Accordinj to the process for the synthesis of dlaaond in this embodiment, the nitrogen |etter is disposed only In the vicinity of the seed crystal, so that the nitre gen removal efficiency is high, end nitrogen is sufficiently removed even by addition of a considerably small amount thereof, whereby Inclusions are decreased.

Fur theme re, Sn is arranged on the seed crystal so that the carbon potential Is increased Just before taken in the crystal, whereby eabedding or Inclusion can be prevented and TIC or ZrC Is prevented froa reaalnlng In the crystal. Thus, colorless and transparent, Indus ion-free diamond crystal can be synthesized at a blgt growth rate.

The folio (Ing exaaples are given in order to Illustrate the present invention In detijl without Halting the saae.

Exaroles Expertaen yl Exaaples l-« In order expertaent was λ measure the diffusion coefficient of carbon in a solvent, an carried out using a heating ceil as shown in Fig. I. Referring to Fig. 2, a cull 10 surrounded by cemented carbide dies 12 were compressed by pistons ll seed each other to generate an inner pressure. Electric current was supplied t< a current ring 14 and a graphite heater 18 to generate heat through the het ter 18 and to naintain uniform the temperatrue Inside the heater 18. In the Interior of the heater 18, pyrophlllite 13 was arranged for insulation and a carbon source 15 and a solvent natal 17 were faced each other and held at a tempi nature of 20 *c higher than the eutectic temperature of the solvent 17 with carbon for 90 minutes, after which the diffusion coefficient was calculated by assuring the length R of a sone 18, in which carbon was diffused and liquid phase appeared.

The diffusion rate was calculated by the following Formula (1) to obtain results as showi in Table 2: -I 7 IE 920846 iS i io ta g “» T x «9 IA c* © IA O ci o X m Table U) U» O . t) X o Φ g n co o P V X ° g o » S > . - id | s j? £ s e o i. i- Sr-*- o q «£ d'C (1) dl dl‘ In which t - tine; D · diffusion coefficient (diffusion rate); C carbon concentration, M - saturated concentration and 1 *= distance.

• I ' * The following Formila (2) waa derived froa Fomula (1): i ί· i (1 - erf( (2) DI Foraula (2) wap Fomula (3): C/M developed In a quadratic expression to give the following )1 IB) DI 2 DI was changed to obtain the constants, α ·, β ,. and β * by changing heating tine t. The diffusion coefficient D was estimated by those constants. of a single crystal was carried out in a cell shown In Fig. 1 i|e how the color of a synthesized diamond, the absorption spectrun the infrared range and the aaount of netal lie Inpurl ties in the dnged depending upon the variety of solvents. Referring to was arranged in ceaented carbide dies 2 and a pressure was produced between qpper and lower pistons l faced each other using pyrophllllte 3 BS a COeoresslrillR nftdleB Fleetrle currant wae pooood through a current »ii< T and a graphite heater 8 to generate heat through the heater 8 and to obtain such a tenperature gradient that the oentrai part of the cell was at the highest The distance 1 Synthesis so as to exanl of nitrogen in crystal were c Fig. 1, a cell tesiperature and the upper end lower end parts were at the lowest tenperature. λ carbon source 1 and a crystal difference T oc 4, solvent 5 and seed crystal 8 were arranged as shown in Fig. 9 was epitaxially grown on the seed crystal 8 by a tesiperature stirred on the carbon source 4 and seed crystal 8.

- I a IE 920846 Examples 1 to 6 ul In d synthesis chamber surrounded by a heater 4 were arranged a construction consisting of a seed crystal 1, a solvent aetal source 2, and an Al-activity Increasing naterial in suitable in Pig. 7. to ezaalne and confira the advanatges given thereaetal had a coaposltlon of Pe- 40 X Co- 1 % Al (weight ratio) as the Al-activity Increasing aaterial and arranged In the ι sheet of 0-1 na In thickness between the carbon source 2 and 3. The aaount of Pb was 0.5 weight X based on the solvent 25 ttaes as auch as the activity of Al when 4 weight X of Al value was deterained assuaing that the activity of Al depends 4tlo of the solvent to Al.

Fig. T, the sample-arranged synthesis ohanber was set In an foerating ultra-high pressure and high teaperature as shown in 1 alned at a pressure of 5. 8 flPa and a teaperature of 1350 τ . sis. the resulting single crystal was subjected to ohservadent of the color, nitrogen concentration and aetal content, forlwents were carried out aa to In, BI and Cd as Al-activity tals and for comparison, tests were carried out as to a sanple -activity increasing aaterial and another sample containing (Increasing aaterial and having an Al content of 4 weight X >. The test results are shown in Table 3.

In a diemop standard sample 3 and a carbon aannar, as show$ by.

The solven and Pb was used fora of a thin the solvent net so as to give 1 was added. This on the weight r Aa shown apparatus for g Fig. 1 and aain After the synth^ tion or measure Slailsr ex; Increasing aatei containing no A no Al-actlvlty (Exaaples 2 to ( -SOIE 920846 Activity Increasing Material Example 1 Pb Table 2 In 3 3 BI Cd 6 no 6 no Aaount of Actlv Increasing Mate ty -lal 0.5 2.0 1.2 1.0 - - (wt X) Shape of Activl Increasing Mate y '|al thin sheet powder powder thin sheet - - Aaount of Al Ad (X) led 1.0 1.0 1.0 1.0 1.0 4.0 Color of 8lngle Crystal colorless, transoarent * * light vellow colorless, transoarent Nitrogen Concentration In Sing' e <0.4 <0.4 <0.4 <0.4 0.9 <0.4 Crystal (ppa) Metal Content (wt X) <0.5 <0.6 <0.5 <0.5 <0.5 1.7 (note); saae as left As evident fron Table 3, when such a material as capable of Increasing I · the activity of Al was added, the color of the single crystal was colorless and transparent and Inclusion was less as represented by a aetal content of at nost 0.6 weight X.

On the other hand, when an activity Increasing asterlal was not added even if 1 weight X of Al was added, the crystal colored light yellow and had a high nitrogen concentration. For obtaining a colorless and transparent crystal without adding activity Increasing material, about 4 weight x or Al was re-IIIE 920846 qulred and wherj the crystal growth was carried out at the sane growth rate aa in these Exaaplies 1 to 4, it was difficult to grow a good quality crystal with a high aetal content.

Examples T to 10 Example l Table 4 Exaaple T 8 8 10 Activity Increasing Material Amount of Actlv Increasing Material (wt X) Pb In BI Cd 0.3 4.5 0.3 4.2 1.0 1.0 1.0 1.0 Aaount of Al Adqed m Color of Single Crystal light colorless, light colorless, yellow transparent yellow transparent Nitrogen Concentration in single Crystal (pop 0.8 <0.4 0.8 <0.4 <0.5 <1.2 <0.5 <1.0 Metal Content (wt X) As evident rial was at nost Froa Table 4, If the aaount of the activity increasing mate0.3 weight X» there was little effect of accelerating reaoval of nitrogen in tke crystal and the crystal colored light yellow, while'if it was at least 4.0 solvent metal in quality crystal.

Weight X, the crystal was colorless, but Inclusion of the the crystal was Increased and it was difficult to grow a good -i iIE 920846 Exapples ϊ tg.lj enperature gradient method in the stable region of diaaond ), diamond of 0.6 to 0.8 caret was grown on a seed crystal e synthesis solvent, there was used an Pe-Co alloy to which e added to obtain results shown in Table 5. The nitrogen cone crystal was determined by ESR (electron-spin resonance) and ijclusion of the solvent was eeasured by a nagnetic balance. Table 5 Examples ia Using the (5.4 GPt. 132O’C for 60 hours.

TI, Al and C wei central ion In t) the anount of Solvent Composition (wt x) Color AeoiBit of Nitro^pn (PP·) Inclusion of SAdlvent {wt X) Possibility of Decorative Ude Rote 11 12 13 14 Fe-40 Co- Pe-40 Co- Pe-40 Co- Pe-40Co- 0.3 TI 0.6 Ti 0.6 Al-0. 5 Tl 0.5A1-1 H B B P 0.95 0.2 0.2 i 0.1 » 1.5 2.1 0.3 0.3 nearly eero very low yes yes comparison comparison our invention our invention 11IE 920846 Solvent Compos1 (wt X) Color Aaount of Nitro (PP·) inclusion of So (wt X) Possibility of Decorative ι Note Table 5 (continued) Bxaaples 16 15 17 18 ;ion Fe-40 Co- Fe-40 Co- Fe-40 Co- Fe-40Co- 0.5 A1-7TI 3 Al-1.2 Tl 6 Al-i. 2 Tl 3A1-10 Tl F r F F. ien < 0.1 t 0.1 « 0.1 a 0.1 vent 0.4 0.4 1.1 1.5 ie yes yes low very low : our Invention our Invention comparison comparison i. Table 5. when only Tl was added, the color grade was at least As shown H In an aaount Increased, thus The lnclud Al to obtain a the including ai addition of 10 the solvent and As explained end quality cry and 0.5 « ΤΙ X Zn was used Ins Examples 11 Of 0.5 weight X and the including aaount of the solvent was deteriorating the worth as decorative use. ng aaount of the solvent was largely decreased by Increasing jhJod quality crystal. However, when 5 weight X of Al was added, iqunt of the solvent was increased. Even when Al was added, iqight X of Tl results in Inorease of the including aaount of a good quality crystal was not obtained. above, the additive range of Al and Tl whereby a good color ^tal can be obtained are repectively 0.5 s Al ί 3 (weight X) (weight X). Purtheraore, when Sn, In, Ag, Cu, Cs, Pb, Sb or 1 ead of Al, similar results were obtained, to 26 Using the (5.3 GPa, 132 The so 1 vent was!prepared by previously preparing an ingot of an alloy, pulvertng the ingot aAd elxlng the resulting powder with carbon powder. The alloy I had a composition of Fe-Co-Ni to which Zr, Bf, V or Tl had been added as a nitrogen getter and Sn, In, Oa or Zn bad been added as a viscosity lowering material.

The synthesized crystal was worked in a disk and subjected to spectroscopic analysis of W, visible and tnfrared wave ranges and to examination of carbides and nl< tides in the crystal by Beans of a transalssion electron mlcroscope. Adaptab lity of the crystal whether it can be used as a window materlei or not was Judgid by spectroscopic analysis and a si cr os cope to obtain results shown in Table I Table β Bxanples Jft.

Solvent Composition (wt X) Spectroscopic Analysis Presence of Carty tides and Nitrides Adaptability to Window Material Note Fe-30Co-10Nl- Fe-iOCo2Zr-lSn ΙβΝΙ-SBf Fe-30C010N1-2ZT no absorption, good * upper and lower parts not found cf crystal Fe-40Co-15Nl3Bf-30in lower part of crystal not found eneultable suitable unsuitable comparison our Invention comparison suitable our invention -I iIE 920846 Solvent Coopoa (wt X) Spectroscopic Analysis Presence of Caribldes and Nitrides Adaptability to Window Material Note tlon Table 6 (continued) Exaaples 23 24 25 _ 20 Pe-25Co- Fe-25C0-25Wi- Fe-lOCo- Fe-10Co-40NJ - 25N1-2.6V 26V-1.50a 40N1-3.5TI 3.5ΤΙ-2ΖΓ no absorption, good lower part of crystal not found unsuitable suitable comparison our invention upper part of vrywlal unsuitable coaparlson not found suitable our invention As evident from Table β, when only the nitrogen getter was added, carbides and nitrides (n Inly oarbldes) were foraed and included In the crystal and the resulting crystal could not be used as a window aaterlal. When Sn, In, Ga or Zn.was adted, on the other hand, the earbdies and nitrides were floated or preciplated Iii a short tlae and thus not Included in the crystal to obtain a good quality crystal. t Example 27 ; carbon powder and Zr powder with varied grain diameters were added to an Fe-βο Co alloy ppwder and calcined to prepare a solvent to exanlne the addition on the grain dlaaeter of the nitrogen getter. The Zr powder was used in a proportion of 1.5 weight X.

Using the tsaperature gradient aethod at an ultra-high pressure and a high i tenperature (5-S GPa, 1330^), geo atone of about 0.4 to 0.0 carat was obtained, The results are ! fiown in the following table.

Weight of Diaaond ( Synthetic carat) Table 7 2 am Zr Grain Diameter 1 ma 5 Hl 10 ma 0.55 0.59 0.42 0.51 Nitrogen content (PP«> 0.1 £ 0.1 0.2 0.5 Color Gra la G F B K Solvent C intent (wt X 1.9 0.9 0.2 0.2 Table 7· It was found suitable that Zr powder had a grain dlato 1 n. Stellar results were obtained as to TI, Bf, v, Ta As shown 1* meter of 10 u a and Nb.

Examples 20 To an Fe-51 of 0.2 ppm to 2 conductor.

Using the temperature (5.5 shown in the fo Co- 1.5 Al-1.5 TI- 4.5 C alloy was added B or Ge In an awount 5 weight X to exaalne the addition effect of the p-type sealeaperature gradient method at an ultra-high pressure and a high GPa), diamond was synthesized for 55 hours to obtain results lowing table. 7 IE 920846 Table 8 Example 28 Example 29 Example 30 Exaiiple 31 * Synthesis Temperature ( ) 1330 1330 1320 1320 Amount of Added B Ga Ga Elements no (0.2 ppm) (0.4 wt X) (2.5 wt X) Height of Synthetic Diamond i J 112 110 105 125 Color· F B E E Infrared Absorp- tlon Coefficient «« not found not found not found not found Solvent Content (wt X) 0.3 0.3 0.4 1.4 (Note): · Grade Standard of Natural Dtanond Gen As shown in Table 8, diamond with a color grade of E that had not been obtained before wis obtained by adding B or Ge.

Example 88 As a raw material of a solvent, high purity Pe powder with a grain diameter of SO to (00 u a, Co powder and graphite powder were used and mixed in a proportion of Fd : Co : C 60 : 40 : 4.5 by weight. In addition, an A1TI Intermetallic ccmpound with an average grain diameter of 50 ^m containing about 5 weight 1 A1T1 i was added in an amount of 1 weight X to the solvent and adequately nixed. The mixed powder was molded, degassed and calcined to obtain a solven with a diameter of 20 aa and a thickness of 10 mm. As a carbon source, theje was used diamond powder and as a seed crystal, there were - J I IE 920846 used three dlaiond crystals of about 600 m m In dlaaeter. in a cons was set within free, high qua ruction of a sample chamber as shown in Pig. 12, the assembly a heater 5 in auch a manner that a temperature gradient of about 30 ΐ was provided between the carbon source 1 and seed crystals 3 and maintained at a pressure of 5.5 GPa and a temperature of 1300 ΐ for 70 hours In an ultra-high pressure producing apparatus, thereby synthesizing diamond. Consequen ly, three colorless and transparent, substantially inclusionIty Ila type diamond crystals of 0.7 to 0.9 carat ware obtained all of which hdd a nitrogen concentration of at most 0.1 ppm, measured by ESS, and an tnclusicp concentration of at most 0.3 weight X, measured by a magnetic balance.

Examples 36- to 35 Synthesis except varying >f diamond was oarried out in an analogous manner to Example 32 he amount of the A1T1 Intermetallic compound powder in 0.5. 2.0 and 4.0 weight X based on the amount of the solvent aetal. thus obtaining good quality Ili'type diamond crystals of 0.8 carat in any cuss, whose nitroI gen concentratioms and inclusion concentrations, measured similarly, were shown In Table 9 with those of Exaaple 32: Amount of Mil (wt X) Amount of Nitrogen (PP·) Amount of delusion (wt X) Example 33 Table 9 32 84 35 0.5 1.0 2.0 4.0 9.1-0.2 <0.1 <0.1 <0.1 <0.3 <0.3 <0.3 0.3-0.6 When the tlally colorless a» unt of nitrogen Is less than 0.2 ppa, the crystal is substanand transparent and there is no problem on use of the dlaaond for decoration and optical parts. When the aaount of Inclusion is less then 0-& weight X, the inclusion Is distributed only in the vicinity of the seed crystal, that is. In such a Halted part of the lower part of the crystal that the Inclusion can readily be reaoved by sone polishing and there arises no probleu. Therefore, the crystals have such quality that they can be applied to decorative use and opttoal parts. The growth rate Is 2 to 2.5 ag/hr, which uurrespuiida lu «t lea at 2 tinea of the critical rate for synthesizing a slallar crystal in the frlor art.

Exaaple 36 Synthesis cf dlaaond crystal was carried out in an analogous Banner to Exaaple 32 excelt using an AlEr intermetallic coapound powder Instead of the AlTi intermetallic coapound powder, thus obtaining a good quality dlaaond of Ila type substantially slallar to that of Exaaple 32.

Exaaple 37 Synthesis cf dlaaond crystal was carried out In an analogous Banner to Exaaple 32 excelt using an AlHf I nt erne tai lie coapound powder Instead of the A1T1 Intermetallic coapound powder, thus obtaining a good quality dlaaond of Ha type substantially slallar to that of Exaaple 32.

Example 38 Synthesis cf dlaaond orystal was carried out in an analogous Banner to Exaaplo 32 oxooit using an A1T1 Interaetatllc coapound powder containing about 20 x of AlTi instead of. the AITt Intermetallic compound powder, thus obtaining a gooc quality diamond of Ila type substantially slallar to that of Example 32.

Exaaple 39 Synthesis cf dlaaond crystal was carried out In an analogous Banner to Exaaple 32 excelt using an Al i TI tnteraetallic coapound powder containing about 10 X of AljTI Instead of the AlTi tnteraetallic coapound powder, thus obtaining a gooc} quality diamond of Ila type substantially slallar to that of Exaaple 32.

I - I I IE 920846 Example 40 Synthesis ,f diamond crystal vas carried out in an analogous manner to Example 32 except using an Al » V intermetallic compound powder Instead of the ic compound powder, thus obtaining a good quality diamond nf Ila type substantially similar to that of Exasple 32.

Example <1 Synthesis if diamond crystal was carried out in an analogous manner to Example 32 exceit using an Al i Hb intermetallic compound powder instead of tho AlTi intermetallic cospound powder, thus obtaining a good quality diamond of lla type substantially similar to that of Example 32.

Example 42 Synthesis i f diamond crystal was oarried out in an analogous manner to Example 32 except using, as a raw material of a solvent, high purity Fe powder with a grain dhmeter of BO to 100 am, Hl powder, Co powder and graphite powder and mixiig them in a proportion of Pe : Hi : Co : C = 60 : 30 : 10 : 4.2 by weight, thus similar to that Example <3 obtaining a good quality diamond of Ila type substantially of Example 32.

Synthesis of diamond orystal was carried out in an analogous manner to Example 32 except using, as a raw material of a solvent, high purity Fe powder with a grain dlaueter of 50 to 100 μι, Ni powder, Nn powder and graphite powder and mixing them in a proportion of Fe s Hi : Nn : C - 60 : 30 :10 : 4.0 by weight, thus >btain(ng a good quality diamond of Ila type substantially similar to that >!r Example 32.

Example 44 Synthesis o \ diamond crystal was carried out in an analogous manner to Example 32 excep using, as a raw material of a solvent, high purity Fe powder with a grain dlaipter of 60 to 100 sm, Ni powder and graphite powder and mixing them In a obtaining a good proportion of Fe : Hl : C B 70 : 30 : 3.5 by weight, thus quality diamond of Ila type substantially similar to that - < 1 IE 920846 of Example 32. Example 45 Synthesis bf diamond crystal was carried out in an analogous manner to Example 32 except using, as a raw material of a solvent, high purity Co powder with a grain dlimeter of 60 to 100 s m and graphite powder, mixing them In a proportion of Cp i C 100 : 4.7 by weight and adjusting the synthetic temperto 1350 thus obtaining a good quality diamond of Ila type mllar to that of Example 82. ature condition substantially s Example 46 Synthesis Example 32 exce if diamond crystal was carried out in an analogous manner to it usings as a raw material of a solvent, high purity N1 powder with a grain diumeter of 50 to 100 « ami graphite powder, aixlng them in a proportion of N ature condition substantially s Example 47 : C 100 : 4.2 by weight and adjusting the synthetic temperto 1350 *C, thus obtaining a good quality diamond of Ha type mllar to that of Example 32.

Synthesis it diamond crystal was carried out in an analogous Banner to Example 32 exce t adding 0.5 weight X of an A1T1 intermetallic coapound powder of an Aizr intermetallic compound powder Instead of adding e A1TI intermetallic coapound powder to the aetal solvent, and 0.5 weight 1 weight X of ti thus obtaining < good quality diamond of Ila type substantially slailar to that of Bxample Example 48 32. to 53 or Al powder wit tion amount ther Synthesis of diaaond crystal was carried out in an analogous Banner to Example 32 excepft. adding a TI powder with an average grain diaaeter of 50 » a fc. an average grain diaaeter of 50 < a with changing the addlspf Instead of adding the A1T1 Intermetallic compound powder to the aetal sol rent. The measured results of the nitrogen concentration and rcentratlon of the resulting diamonds are shown In Table 10. the inclusion co 2 τ,&ι, 10 Example 50 51 52 53 48 48 Amount of 11 (wt X) 4 1 0 0 0 • 1 Amount of ' i (wt X) 0 0 0 1 2 1 Amount of lltrogen (ppm) a 7 88 0.2 < 0.1 < 0.1 Amount of ncluBlon (wt X) 2.5 0.4 < 0.8 1.3 2.6 0.5 All the crystals had large amounts of nitrogen and Inclusion and colored so yellow that |hey could not be applied to decorative use and optical parts.

Example 54 Synthesis nf diamond crystal was carried out ln an analogous manner to Example 32 except using, aa a raw material of a solvent, high purity Fe powder with a grain dlimeter of 50 to 100 mm, Nl powder and Co powder and eixlng then In a proportion of Fe s Nl : Co = 60 : 30 : 10 by weight, and adding no graphite. eonsequerr iy, the seed crystals were completely dissolved In the solvent and disappeared Example 65 There was found no growth of diamond.

Synthesis if diamond crystal was carried out In an analogous manner to Exanple 32 except using, as a raw aaterlal of a solvent, high purity Pe powder wtth a grain di< meter of 50 to 100 u a, Nl powder, Co powder and graphite powder and alxlrg the· In a proportion of Fe : Nl : Co : C = 80 : 30 : 10 : 7 by weight. Consequently, a number of spontaneous diamond nucleations took place from othei sites than the seed crystals and the crystals Interfered with each other, thu hardly obtaining good quality crystal.

S IE 920846 Exaaple 56 ness of 10 mm. crystal, there In a constructl within a heater was provided be This examile was carried out so aa to examine the effect obtained by adding a low vlscislty aetal and a nitrogen getter netal In the fora of an InterMtalllc coapomd thereof. Aa the intermetallic compound, Sn Tl· was used.

As a raw notarial of a solvent, high purity Pe powder with a grain diameter of SO to ioo » a, Co powder and graphite powder were used and alxed In a proportion of le : Co : C > 60 : 40 : 4.5 by weight. In addition, an Sn« Tl, Intermetallic compound with an average grain diameter of SQ am. as an addltlvo, wee added In ar .amount of 1 weight X (Sn 0.5 wt x, Tl 0.5 wt X) to the solvent metal (except | naphlte) and adequately mixed. The mixed powder was molded, degassed end oalclned to obtain a solvent with s diameter of 20 aa and a thlckas a carbon source, there was used diamond powder and as a seed tere used three diamond crystals of about 500« m in diameter. hi of a sample chamber as shown in Fig. 12, the assembly was set ί in such a manner that a temperature gradient of about 30 ween the carbon source 1 and seed crystals 3 and maintained at a pressure o;‘ 5.5 GPa and a temperature Of 1300X for 70 hours tn an ultrai educing apparatus, thereby synthesising dlaaond. y, three colorless and transparent, substantially inclusionhigh pressure p Consequent free, high quell ty Ila type diamond crystals of 0.7 to O.B carat were obtained all of which hat and an incluslor vacuum, complete a nitrogen concentration of at most 0.1 ppm, measured by BSB, concentration of at moat 0.3 weight X, measured by a magnetic balance. The coftqr grade was *P.

On the othef hand, the same composition as described above was melted in y alloyed and used as a solvent. Nhen diamond was synthesized under the same cbhdltions as described above, there was obtained one having a nitrogen concentration of 0.2 ppa and a color grade of B. When adding Tl and removal effect wax more than In the case of adding in the form |c oompound.

Sn, the nitrogen of an lnteraetal -44IE 920846 Examples 5 to 50 Synthesis Example 61 Synthesis Example 82 Synthesis Example 63 Synthesis Example 64 Sy nt heels diamond crystal was carried out in an analogous manner to Example 56 excelt using, as a raw material of a solvent, high purity Fe powder with a grain dhaeter of 50 to 100 sa, Hi powder, Co powder and graphite powder and alxirg thei in a proportion of Pe : Ml ; Co : C = 60 : 30 ; 10 : 4.2 by weight, thus Similar to that obtaining a good quality diamond of Ila type substantially of Example 56. -45IE 920846 Example 6> Synthesis of diamond crystal was carried out in an analogous manner to Example 68 except using, as a raw material of a solvent, high purity Fe powder with a grain d powder and mix by weight, thw similar to that Example 81 ameter of $0 to 100 am, Ni powder, Nn powder and graphite ng them in a proportion of Ft : Ni : Hn : C ~ 80 i 30 s 10 : 4.0 obtaining a good quality diamond of Ila type substantially of Example 58.

Synthesis of diamond crystal was oarrted out In an analogous manner to Example 56 except using, as a raw material of a solvent, high purity Fe powder with a grain dl mixing them in ameter of 80 to 100 am, NI powder and graphite powder and i proportion of Fe : NI : C ’ 70 : SO : 3.5 by weight, thus obtaining a goo J quality diamond of Ila type substantially similar to that of Example 8β.

Example 87 Synthesis bf diamond crystal was carried out in an analogous manner to Example 68 except using, as a raw material of a solvent, high purity Co powder with a grain dimeter of 50 to 100 am and graphite powder, mixing them in a proportion of Co : C = 100 : 4.7 by weight and adjusting the synthetic temperature condition to 1350 *c, thus obtaining a good quality diamond of Ila type substantially s milar to that of Example 58.

Example 68 Synthesis Example 60 Synthesis of diamond crystal was carried out in an analogous manner to -44IE 920846 Example 56 except adding 1 weight % of TI powder having an average grain dla* meter of 50 and not adding the Sn.TI· Intermetallic compound, thus obtaining a crystal hiving a small amount of nitrogen, i.e. 0.2 ppm. However, the growth quantity was about 0.8 carat per one crystal. A large aaount of TIC was found In tha crystal and Inclusion of the solvent reached about 1.0 weight X to give no go Example 70 xl crystal.

Wien the procedure of Example 56 was repeated except using 15 weight X of the sniTt· 1 itermetallic compound to synthesize diamond crystal, the cryStal grown from crystal.

Example 71 the seed crystal was poiycrystalline to give no good single Synthesis <>f diamond crystal was carried out In an analogous manner to Example 56 except adding 0.5 weight X of Sn powder and 0.5 weight X of Ti powder each having an uyerage grain diameter of 50 s a and not adding the SmTI intermetallic ciepound, thus obtaining a crystal of about 0.8 carat having a small aaount of nitrogen, I.e. 0.2 ppm but having somewhat a large aaount of inclusion, I.e. 0.7 weight X.

Example 72 Synthesis 60 : 30 : 10 by weight, and adding no graphite. Consequent ly, the seed crystals were completely dissolved in the solvent and disappeared. Example 73 There was found no growth of diamond.

Synthesis of1 diamond crystal was carried out in an analogous manner to Example 56 except using, as S raw material of a solvent, high purity Fe powder with a grain diaaeter of 50 to 100 it m, HI powder, Co powder and graphite powder and mlxlnp then In a proportion of Fe : Nl : Co : C 50 : 30 : 10 : 7 - 4 7 IE 920846 by weight. Consequently, a number of spontaneous diamond nucleations took place from othir sites than the seed crystals and the crystals interfered with each other, this hardly obtaining good quality crystal.

Bxamole In a cons’Auction of a sample chamber as shown in Pig. 11, diamond powder was used as a qarbon source t and an alloy having a composition of Fe : Co : .5 In the fora of a diameter of 20 aa and a thickness of 10 mm was used as a ialvent metal 1. As a nitrogen getter 3 st the solvent aetal side, there was disposed a TI sheet having a diaaeter of 20 m and a thickness of 0.1 na and as a low viscosity metal 4 at the seed crystal! side, there was sheet having a diameter of 20 aa and a thickness of 0.1 aa. tlae, the amount of Ti was 1 voluae X to the solvent and that of X to the sotvent. as a seed crystal 5, three dlaaond crystals it a diaaeter of 500 * a were used. The sample chamber was set siich a manner that a temperature gradient of about 30 *c was disposed an Al During the same Al was 1 volune each having abo in a heater in provided betwee n the carbon aouroe and seed crystal and maintained at a preand a tenperature of I300r for 70 hoars in an ultra-high Ag apparatus, thereby synthesizing dlaaond. j, three coldrless end transparent, substantially inclusionty Ha type diamond crystals of 0.7 to 0.9 carat were obtained a nitrogen concentration of at most 0. l ppa, measured by ESR, concentration of at most 0.3 weight X, aeasured by a magnetic ssure of.5.5 CPs pressure produc Consequent free, high qual all of which he< and an tnclusloi balance.

Examples 71 Diamond wad synthesized in an analogous manner to Example 74 except changing the thickness of Ti and Al sheets as shown in Table ll. A good quality Ila type diamond crystal of about 0.8 carat was obtained having a nitrogen concentration and inclusion concentration measured as shown in Table 11. The results I of Exeaple 74 ar» also shown in Table 11.

-IIIE 920846 Example —UIL.

Thickness (m Addition Aaouht to Solvent (v01 X) ALThickness (mn Addition Asouit to Solvent (vii X) Amount of Mtrocpn <ΡΡ·> Amount of Inclusion (wt X, 0.1 0.1 < 0.1 < 0.3 Table ii 0.1 0.05 0.5 < 0.1 < 0.3 TO 0.05 0.5 0.05 0.B 0.1-0.2 < 0.3 0.2 0.1 < 0.1 0.3-0.4 0.4 0.1 < 0.1 0.4-0.5 iiount of nitrogen is less than 0.2 ppm In the diamond crystal, $qbetantlel ly colorless and transparent and there Is no problem qaond for decoration and optical parts. When the aaount of s than O.S weight x, the Inclusion is distributed only in the seed crystal,, that is, in such a Halted part of the lower 4 Is 2 to 2.5 ag/hr, which corresponds to at least 2 tines of β for synthesising a slailar crystal in the prior art.

When the ai the crystal is on use of the d inclusion is lei vicinity of the part of the cry and there arise! such quality thi The growth rate the critical ra Example 70 Synthesis Example 74 of Ila type sub: cf except dlaaond crystal was carried out In an analogous manner to using Zr instead of TI, thus obtaining a good quality dlaaond sftiantlally slailar to that of Exaaple 74. - 4 I Example 80 Synthesis Example 81 Synthesis it diaaond oryetal was carried out in an analogous manner to Example 74 excep using an alloy of Pe > Ml ί Co s C = 80 : 90 : 10 : 4.2 (weight ratio) qs a solvent metal, thus obtaining a good quality diamond of Ila type substantially similar to that of Example 74.

Example 82 Synthesis it diamond crystal was carried out in an analogous manner to f Example 74 excep using an alloy of Pe : Nl : Mn : C = 80 : 90 .* 10 : 4.0 (weight ratio) is a solvent wetal, thus obtaining a good quality diamond of Ila type substantia Example 88 ly similar to that of Example 74.

Synthesis (f diamond crystal was carried out In an analogous manner to Example 74 excep using an alloy of Fe : Ml : C = 70 : 80 : 3.5 (weight ratio) as a solvent me’ dl, thus obtaining a good quality diamond of Ha type substantially similar iq that Of Example 74.

Example 84 Synthesis p diamond crystal was carried out in an analogous manner to Example 74 except using, a Ti sheet with a thickness of 0.05 mm and a zr sheet with a thicknesiof 0.05 m, which were stacked, Instead of the Tl sheet with a thickness of (.1 am, thus obtaining a good quality diaaond of Ila type substantially slal ar to that of Example 74.

Example 85 When diamond was synthesized in an analogous manner to Example 74 except not disposing tie Al sheet, consequently, diamond was hardly grown and a film I of Tic was formd on the seed crystal. was synthesized in an analogous manner to Example 74 except TI sheet and changing the thickness of the Al sheet in 0.5 . consequently, a dlanond crystal of about 0.8 carat was obred lightly yellowish and contained nore Inclusion. The nitro n was 2 ppn and the amount of the Inclusion was 3 weight X.

Example 8( When diamdnd not disposing nm (5 volume X) talned, but gen concentrat lb; E*d»Ple 87 the owl When diem changing the t a diamond crystal more inclusion but the amount Example 88 was synthesized In an analogous manner to Example 74 except hjlckness of the Al sheet in 0.5 nm (S volume X), consequently, of about 0.8 caret having less nitrogen content but contalng tas obtained. The nitrogen concentration was at most 0.1 ppm. it the inclusion reached about 3 weight X.

When dianop changing the th a diamond cryst more Inclusion but the amount .

Example 89 id was synthesized in an analogous manner to Example 74 except pkness of the TI sheet In 1.0 mm (10 volume X), consequently, of about 0.8 carat having less nitrogen content but contalng vie obtadned. The nitrogen concentration was at moat 0.1 ppm, the inclusion reached about 5 weight X.

Hl Synthesis Example 74 except Fe i NI : Co = the seed cryste There was found Example 90 diamond crystal was carried out In an analogous manner to using, as a solvent, an alloy consisting of a composition of 50 : 30 : 10 by weight, and adding no'graphite. Consequently, S were completely dissolved In the solvent and disappeared, no growth of diamond.

Synthesis Example 74 exce Fe : NI : Co nucleation of d the crystals In diamond crystal was carried out in an analogous manner to using, as a solvent, an alloy consisting of a composition of 60 : 30 : 10 by weight. Consequently, a number of spontaneous amend took place from other sites than the seed crystals and t tjerfered with each other, thus hardly obtaining a good quality -siit crystal.

ExaspIe 9 in · cons1 ruction of a sanple chamber as shown in Pig. Π. diamond powder was used as a carbon source 1 and an alloy having a composition of Pe : Co : C 8 60 : 40 * c .6 (by weight) In the fora of a diameter of 20 aa and a thickness of 10 na was used as a solvent aetal 2. As a nitrogen getter 3 at the solvent aetal side, there was used a Ti sheet having a diameter of 20 mm and a thickness of 0.1 am was used an Sn During the sane and as a low viscosity aetal 4 at the seed crystall side» there sheet having a diameter of 20 aa and a thickness of o.i aa. jtlae, the aaount of TI waa 1 volume X to the solvent and that of Sn was 1 volbme X td the solvent. As a seed crystal S, three diamond crystals each havl ife about a disaster of 500 m m were used. The sample chamber was set In a heater In such a Banner that a temperature gradient of about SO between the carbon souroe and seed crystal and maintained at 3 GPa and a temperature of 1300 T5 for 70 hours in an ultrat was provided a pressure of 5 high pressure producing apparatus, thereby synthesizing diamond.

Consequent y, three colorless and transparent, substantially inclysionfree, high quality Ila type diamond crystals of 0.7 to 0.9 carat were obtained all of which ha< and an Inclusior balance.

Example 82 a nitrogen concentration of at most 0.1 ppm, aeasured by ESB, concentration of at aost 0.3 weight X, measured by a magnetic Synthesis of diamond crystal was carried out In an analogous manner to Example 01 excepusing a Zr sheet with a diameter of 20 mm and a thickness of 0.1 mm (corresponding to 1 voiuae % to the solvent metal) as a nitrogen getter 3, thus obtaining good quality diamond of Ila type substantially similar to that of Example 81.

Example 83 Synthesis o:' diamond crystal was carried out In an analogous manner to Example 91 except using a Rf sheet with a diameter of 20 an and a thickness of - 5 I IE 920846 0.1 nn (corresponding to 1 volune % to the solvent netal) as a nitrogen getter 8, thus ohtelntig a good quality dianond of Ila type substantially alnliar to that of Exanple 91.

Example 94 Synthesis O.B mm (corresponding to 1 volune % to the solvent netal) as a nitrogen getter 3, thus obtainltg a good quality dianond of Ila type substantial ly slsllar to that of Exanjjie 91.

Exanple 95 Synthesis cf dianond crystal was carried out In an analogous nanner to Exanple 91 excelt using, as a nitrogen getter 3, a T1 sheet with a diameter of 20 an and a thlqkneas of 0.1 na (corresponding to 1 volune % to the solvent sheet with n diameter of 20 nm and a thickness of 0.l nn (corMolune X to the solvent netal), which were stacked In such a Til sheet was contacted with the solvent side, thus obtaining a good quality qianond of Ila type subtantially slsllar to that of Exanple 91.

Example 98 netal) and an Al responding to 1 nanner that the Synthesis of diamond crystal was carried out in an analogous nanner to Example 91 except using, as a nitrogen getter 3, a Zr sheet with a diameter of 20 m and a thickness of 0.1 nm (corresponding to 1 volune X to the solvent sheet with a diameter of 20 m and a thickness of 0. l nn (corrolune X to the solvent netal), which were stacked in such a fr sheet was contacted with the solvent side, thus obtaining lamond of Ila type subtantially sinilar to that of Example 91. netal) and an Al responding to 1 manner that the a good quality d Exanple 97 Synthesis o Exanple 91 excep Fe : NI : Co : C I dianond crystal was carried out in an analogous Banner to using, as a solvent, an alloy consisting of a composition of 80 : 30 : 10 : 4.2 by weight, thus obtaining a good quality dianond of Ila type subtantially similar to that of Exanple 91.

-BIIE 920846 of diamond orystal was carried out in an analogous manner to Example 9( Synthesis Example 91 except using, as a solvent, an alloy consisting of s composition of C » 60 : 80 : 10 : 4.0 by weight, thus obtaining a good quality type subtantlally similar to that of Example 91.

Fe : Nl : Mn : diamond of Ila Example M Synthesis |of diamond crystal was carried out in an analogous manner to Example 91 exce# using, as a solvent, an alloy consisting of a composition of Fe : Nl : C « 71 : 30 : 3.6 by weight, thus obtaining a good quality diamond of Ila type subtantlally similar to that of Example 91.

Example 10) >r diamond crystal was carried out In an analogous manner to >t using, as a solvent, an alloy consisting of a composition of 1,7 by weight and adjusting the synthetic temperature condition Synthesis Example 91 exce Co : C » 100 : to 1350 ic. thus·obtaining a good quality diamond of Ila type subtantlally similar to that Example 10 of Example 91.

Synthesis ol diamond crystal was carried out in an analogous manner to Example 91 exce it using, as a solvent, an alloy consisting of a composition of Nl : C 100 : .2 by weight and adjusting the synthetic temperature condition to 1350 thui: obtaining a good quality diamond of Ila type subtantlally of Example 91. similar to that Example 101 d was synthesized in an analogous manner to Example 91 except e Sn sheet, consequently, diamond was hardly grown and a TIC on the surfaoe of the seed crystal. t d was synthesized In an analogous manner to Example 91 except d Sn sheet and using an Al sheet with a diameter of 20 am and ism (corresponding to 6 volume I to the solvent metal), a When dlamoi not disposing tl film was formed Example 101 When dlamoi not disposing tl thickness of 0.( -54IE 920846 colorless and transparent crystal of about 0.8 carat was obtained having a large inclusion content, i.e. 3 weight X.

Exaaple 1(4 When dlamtnd was synthesized in an analogous Banner to Example 01 except not disposing 1 he nitrogen getter 3, consequently, there was obtained a crystal -of lb type wltl $.8 carat, which was substantially free from Inclusion (at most 0.3 weight X), [contained about 80 ppm of nitrogen In substitutional type and colored yellow.

Example 10|8 When diamond was synthesized In an analogous manner to Exaaple 91 except changing the th ckness of the Sn sheet in 0.7 ma (5 volume X to the solvent metal), consequmtly, a good'quality single crystal could not be obtained beng polycrystalline end a number of spontaneous nucleations other sites than the seed crystals. cause of render took place from Example 108 When diamond was synthesized in an analogous manner to Example 91 except changing.the thjekness of the TI sheet in 1.2 mm (12 volume X to the solvent metal) but maintaining the diameter thereof as it was, consequently, there was obtained a crystal of about 0.8 carat with less nitrogen content but aore ininclusion. The nitrogen concentration was at most 0.1 ppm, but the inclusion content reached about 8 weight X.

Example 101 Synthesis of. diamond crystal was carried out In an analogous manner to Example 91 except using, as a solvent, an alloy consisting of a composition of I Pe : Ki : Co = 09 : 30 : 10 by weight, and adding no carbon (C). Consequently, the seed crystal s were completely dissolved in the solvent and disappearedThere was found 4> growth of diamond.

Example 108 Synthesis o Exaaple 91 excep dlaaond crystal was carried out In an analogous aanner to musing, es a solvent, an alloy consisting of a composition of -5 5IE 920846 Fe : Nl : Co : jC = 60 : 30 : 10 : 7 by weight. Consequently, a number of spanI taneous nucleation of diamond took place from other sites than the seed crystals and the crystals Interfered with each other, thus hardly obtaining a good qullty crystal.

As explained above, according to the present invention, a colorless and transparent, sujstantlally Inclusion-free crystal can be synthesized In stable manner. single crystal synthesized by the present Invention can be rhtlve dies and optical parts, in particular, as Infrared optical and econoalcal The dianon applied to deco parts, to diamoid anvils for Infrared spectrometer, ultra-high pressure diamond anvils, prisms (or ΑΤΒ». window materials for Infrared spectroaeter, window materials for las if beaa, etc.

Claims (24)

1. -WHAT IS CLAIMED IS:

1. A process for the synthesis of diasond, which coaprlses, in the synthesis of dlemcnd crystal by the temperature gradient sethod, using, as a solvent for the growth of the crystal, st least one metal selected fron the group e, Co, Hi, Hn and Cr and as s nitrogen getter for the removal of isolvent, at least one metal selected from the group consisting Hf, V, lib and Ta in a proportion of 0.6 to 7 X by weight to the conststing of nitrogen in th« of Al, TI, zr, solvent aetal.

2. The process for the synthesis of diamond as claimed in Claim 1, wherein the solvent contains at least one metal selected froa the group consisting of Co, Hi, Hn and Jjr In addition to Fe as an essential element.

3. The prtcess for the synthesis of diamond as claimed in Claim l, wherein the nitrogen ge ter coritaine at moat I weight X of only Al. allowed to float Ing the crystal

4. The pricess for the synthesis of diamond as claimed In Claim l, wherein the solvent con:ains at. least one member selected from the group consisting of B, Ga, Be, In and Li in a proportion of 0.2 ppm to 2 weight X.

5. 6. .The process for the synthesis of diamond as claimed in Claim 1, wherein 0.3 to 4 weight X of at least one member selected from the group consisting of Pb. In, Cd and 11 is added to the solvent to as to Increase the activity of the nitrogen gel 1er. 6. The precess for the synthesis of dlaaond as claimed in Claim 1, wherein nitrides, carbiqde, oxides, etc. formed by addition of the nitrogen getter are or precipitate before growth of the crystal, thereby preventive· inoiaaten of the nitrides, carbides, oxides, eto.'

6. 7. The process for the synthesis of diamond as claimed in Claim 6, wherein the floating or viscosity elemen ipeclpltating ia oarried out by addition of at least one low selected from the group consisting of Al, Sn. In, Ga, Ag, Cu, Cs, Pb, 8b and Zhi

7. 8. The proiess for the synthesis of diamond as claimed In Claim 1, wherein the low viscosity element is added In an amount of 0.5 to 3 weight X. - 5 7 IE 920846 '

8. 9. Tbe process for the synthesis of diamond as claiaed in Claim 7, wherein the addition of, the low viscosity element is carried out by stacking a aetal sheet consisting of a nitrogen getter aetal and a aetal sheet consisting of the low viscosity element between the solvent aetal and seed crystal.

9. 10. The process fpr the synthesis of diamond as claimed In Clala 7, wherein the low viscosity eleaent is carried out by previously preparing ; coapound thereof with the nitrogen getter aetal and adding the the addition of an Interoetalll Interaetallic c impound.

10. 11. The pricess for the synthesis of diaaond as claiaed In Clain 7, wherein the addition of the low viscosity eleaent is carried out by adding an alloy t6- The pro wherein the add! thereof with thi* nitrogen getter aetal or solvent aetal In the fore of a powder with a diaaeter af 10 sm to 1 am or thin fragaents to the solvent.

11. 12. The prd«ess for the synthesis of diaaond as claiaed in Clala 1. wherein the solvent metii contains 0.1 to β weight X of carbon.

12. 13. The pricess for the synthesis of diamond as claimed in Clala 1. wherein the nitrogen ge< ter Is in Al-X type Intermetallic coapound wherein x represents an eleaent selected froa the group consisting of Ti, Zr, Hf, V, Nb and Ta.

13. 14. The prtoess for the synthesis of diamond as olalaed In Claim 13, wherein the addition aaount of the Al-X type interaetallic compound is 0.1 to 5 weight X based orc the solvent aetal.

14. 15. The process for the synthesis of diamond as claimed in Claia l, wherein the nitrogen getter is an Sn-X type Intermetallic coapound wherein X represents an element selected from the group consisting of Tl, Zr, Hf, V, Mb and Ta. :pss for the synthesis of diaaond as claiaed in Claim 15, :ion amount of the Sn-X type intermetallic coapound is 0.1 to 10 weight x base) on the solvent aetal.

15. 17. A proceih for the symthesla of diamond crystal by the temperature gradient method, rhlch comprises arranging a solvent metal to be contacted with a carbon source, a ranging at least one metal slelected from the group consisting of Tl, Zr and Hf es a nitrogen getter at the solvent metal side between the -31IE 920846 I solvent metal And a seed crystal disposed below the solvent metal and arranging Al et the seed crystal side between them in such a manner that the seed crystal la not contacud with the nitrogen getter, and then starting synthesis of diamond using the thus arranged assembly.

16. 18. The piaceas for the synthesis of diamond crystal as claimed In Claim 17, wherein the solvent metal contains at least one member selected from the group consists o of Fe, Co, Ni, Nn and Cr, and 0.1 to β weight X of carbon.

17. 19. The process for the synthesis of diamond crystal as claimed in Claim pdditlon amount of at least one metal slelected from the group consisting of Th Zr and Bf as a nitrogen getter is 0.2 to S volume X based on the solvent met|u and the addition amount of Al la 0.1 to 2 volume x based on the solvent.

18. 20. A process for the synthesis of diamond single crystal by the tempernethod, which comprises arranging a solvent metal to be contacted mrce. arranging at least one metal slelected from the group conature gradient with a carbon s sisting of Al, 11, Zr and Bf as a nitrogen getter et the solvent metal side between the soil and arranging 8r the seed crystal ent metal and a seed orystal disposed below the solvent netal at the seed crystal side between them in such a manner that Is not contacted with the nitrogen getter, and then starting synthesis of diamond using the thus arranged assembly. SI. The process fot the synthesis of diamond crystal as claimed in Claim iplvent metal contains at least one member selected from the pf Fe, Co, Nl, Nn and Cr, and 0.1 to 6 weight X of carbon. ;bss for the synthesis of diamond single crystal as claimed In 20, wherein the group consisting 22. The pro Claim so, wherei tthe addition amount of at least one aetal slelected from the group consisting I based on the s et Al, Ti, zr and Hf as a nitrogen getter is 0.2 to 10 volume t it vent metal and the addition amount of Sn is 0.1 to 5 volume X based on the so)vent. -BIIE 920846

19. 23. A process as claimed in claim 1 for the synthesis of diamond, substantially as hereinbefore described and exemplified.

20. 24. Diamond whenever synthesized by a process claimed in any one of claims 1 - 16 or 23.

21. 25. A process as claimed in claim 17 for the synthesis of diamond crystal, substantially as hereinbefore described and exemplified.

22. 26. Diamond crystal whenever synthesized by a process claimed in any one of claims 17 - 19 or 25.

23. 27. A process as claimed in claim 20 for the synthesis of diamond single crystal, substantially as hereinbefore described and exemplified.

24. 28. Diamond single crystal, whenever synthesized by a process claimed in any one of claims 20 - 22 or 27.