Why are white LGDs so hard to make?

[lliang_chi]

First, let me just say this forum rocks! (Forgive the pun) I think it SO fascinating to see a new "frontier" being created as LGDs are. It''s really great.

Onto my topic question.

Why are white diamonds so hard to make? And which of the other fancy colors (pink, blue, yellow, black) are easier/harder? Can you make yellow diamonds in the same "pot" as blue? Or is it like making tea & coffee in the same pot?

 

[EEFranklin]

Date: 6/24/2008 12:16:29 PM
Author:lliang_chi
Why are white diamonds so hard to make? And which of the other fancy colors (pink, blue, yellow, black) are easier/harder?

The HPHT (High Pressure High Temperature) growth units create an environment that diamond crystals can grow in. This environment contains a molten metal solution that carbon is dissolved in along with a tiny diamond seed for the carbon to grow off of. The environment needs to be very highly controlled and minor fluctuations can cause the process to fail at producing a gem-quality diamond.

The yellow color comes from nitrogen inside the growth chamber. The nitrogen assists the growth, so a yellow diamond grows quicker. The nitrogen becomes part of the diamond lattice and it is what creates the yellow color in all diamonds. Blue diamonds can be made by replacing the nitrogen with boron during the growth. By doing this, the blues grow slower than yellows. Removing the nitrogen and boron from the environment, preventing it from becoming part of the finished diamond, is how you create a white, though by doing so, it greatly slows down the growth speed. The slower growth makes the diamond more prone to failure (heavily included, poor color, etc).

This is a great oversimplification of technology that has taken 50 years to get to where it is at today. The other colors (pink, red, green, etc) are done post-growth with as-grown yellows or off-whites through irradiation or annealing.

Can you make yellow diamonds in the same ''pot'' as blue? Or is it like making tea & coffee in the same pot?

In one growth cycle, the machines grow one diamond of one color.

Currently, we can produce polished yellows up to two carats, blues up to 1.25cts and whites up to .75~1.0cts.

 

[lliang_chi]

Eric, thanks for the post. I guess that makes sense. Don''t know if this stumbles into the IP area, but which colored diamonds make which other colors?

E.g. Yellow makes green etc.

 

[kcherian]

Date: 6/25/2008 12:12:43 PM
Author: lliang_chi
Eric, thanks for the post. I guess that makes sense. Don''t know if this stumbles into the IP area, but which colored diamonds make which other colors?

E.g. Yellow makes green etc.

High Pressure – High Temperature (HP-HT) annealing (and also certain types of radiation) are known to induce color changes in diamond, but it is not easy to predict the resulting color in different cases even though the starting color may apparently be the same or similar – there are several factors which could influence the outcome. Some reported examples by a leading technical/research group in the field are listed below, which show the variations in color after HP-HT annealing:

Diamond type Color before HP-HT annealing Color after HP-HT annealing
1a Light brown Pale green
1a Light brown Yellow
1a Light brown Light brown
1a Light brown Yellow
1a Brown Intense yellow
1a Brown Vivid yellow
2a Brown Pink
2a Brown Light pink
2a Brown Colorless

KC

 

[Alexei Zarakhani]

Date: 6/26/2008 2:29:32 AM
Author: kcherian

Date: 6/25/2008 12:12:43 PM

Author: lliang_chi

Eric, thanks for the post. I guess that makes sense. Don''t know if this stumbles into the IP area, but which colored diamonds make which other colors?


E.g. Yellow makes green etc.

High Pressure – High Temperature (HP-HT) annealing (and also certain types of radiation) are known to induce color changes in diamond, but it is not easy to predict the resulting color in different cases even though the starting color may apparently be the same or similar – there are several factors which could influence the outcome. Some reported examples by a leading technical/research group in the field are listed below, which show the variations in color after HP-HT annealing:


Diamond type Color before HP-HT annealing Color after HP-HT annealing

1a Light brown Pale green

1a Light brown Yellow

1a Light brown Light brown

1a Light brown Yellow

1a Brown Intense yellow

1a Brown Vivid yellow

2a Brown Pink

2a Brown Light pink

2a Brown Colorless


KC

Karl(if I may),

This is true for natural diamonds since 1a synthetics do not exist. Also, HPHT-grown 2a diamonds are not brown so your info is not applicable for them as well. However, it may be applied to brown (-ish) CVD-grown 2a diamonds. I''ve seen a lot of those. Unfortunately, it''s not always possible to completely remove brownish hue in those.

Also, from a general education standpoint - HPHT treatment and HPHT synthesis are completely different processes. They have in common only a high pressure high temperature environment, an equipment to create such conditions can be also the same but the rest is different. In absolute majority of cases, HPHT treated diamonds are natural while HPHT grown are man-made.

 

[kcherian]

Date: 6/26/2008 11:31:11 AM
Author: Alexei Zarakhani

Date: 6/26/2008 2:29:32 AM
Author: kcherian

Date: 6/25/2008 12:12:43 PM

Author: lliang_chi

Eric, thanks for the post. I guess that makes sense. Don''t know if this stumbles into the IP area, but which colored diamonds make which other colors?


E.g. Yellow makes green etc.

High Pressure – High Temperature (HP-HT) annealing (and also certain types of radiation) are known to induce color changes in diamond, but it is not easy to predict the resulting color in different cases even though the starting color may apparently be the same or similar – there are several factors which could influence the outcome. Some reported examples by a leading technical/research group in the field are listed below, which show the variations in color after HP-HT annealing:


Diamond type Color before HP-HT annealing Color after HP-HT annealing

1a Light brown Pale green

1a Light brown Yellow

1a Light brown Light brown

1a Light brown Yellow

1a Brown Intense yellow

1a Brown Vivid yellow

2a Brown Pink

2a Brown Light pink

2a Brown Colorless


KC

Karl(if I may),

This is true for natural diamonds since 1a synthetics do not exist. Also, HPHT-grown 2a diamonds are not brown so your info is not applicable for them as well. However, it may be applied to brown (-ish) CVD-grown 2a diamonds. I''ve seen a lot of those. Unfortunately, it''s not always possible to completely remove brownish hue in those.

Also, from a general education standpoint - HPHT treatment and HPHT synthesis are completely different processes. They have in common only a high pressure high temperature environment, an equipment to create such conditions can be also the same but the rest is different. In absolute majority of cases, HPHT treated diamonds are natural while HPHT grown are man-made.

Alexei,

Thanks for your input.

Only some examples - from a much larger list of different types of diamond that were HPHT treated for color change - were mentioned, the intention being only to illustrate the general fact that diamonds of apparently the same initial color need not necessarily yield the same color after HPHT treatment…

Yes, you are right; 1a synthetics do not exist (or are extremely rare). Why, do you think, is it difficult or impossible to form/grow synthetics as type 1a?

Karl

 

[Alexei Zarakhani]

Date: 6/27/2008 3:03:36 AM
Author: kcherian

Date: 6/26/2008 11:31:11 AM


Yes, you are right; 1a synthetics do not exist (or are extremely rare). Why, do you think, is it difficult or impossible to form/grow synthetics as type 1a?


Karl

Karl,

All diamonds, synthetic and natural, in presence of nitrogen grow as type 1b. Nitrogen atoms substitute carbon in a diamond lattice. Natural diamonds, which were initially of type 1b, were exposed to high pressures and temperatures for quite a long period of time - for millions of years. During that time nitrogen atoms migrated to each other forming various aggregations - A-centers, B-centers, N3-centers and platelets. In other words, one can say that natural diamonds were naturally HPHT treated to produce type 1a from initial type 1b. Lab-grown diamonds can also be HPHT treated (in a press) but a period of exposure should be very long (definitely, not days or weeks) to allow nitrogen atoms to diffuse to each other through a tightly packed diamond lattice. Such a long HPHT treatment period makes the whole process not feasible. It''s less costly to grow 2a diamonds, instead.

 

[kcherian]

Date: 6/27/2008 3:01:06 PM
Author: Alexei Zarakhani

Date: 6/27/2008 3:03:36 AM
Author: kcherian

Date: 6/26/2008 11:31:11 AM


Yes, you are right; 1a synthetics do not exist (or are extremely rare). Why, do you think, is it difficult or impossible to form/grow synthetics as type 1a?










Karl

Karl,

All diamonds, synthetic and natural, in presence of nitrogen grow as type 1b. Nitrogen atoms substitute carbon in a diamond lattice. Natural diamonds, which were initially of type 1b, were exposed to high pressures and temperatures for quite a long period of time - for millions of years. During that time nitrogen atoms migrated to each other forming various aggregations - A-centers, B-centers, N3-centers and platelets. In other words, one can say that natural diamonds were naturally HPHT treated to produce type 1a from initial type 1b. Lab-grown diamonds can also be HPHT treated (in a press) but a period of exposure should be very long (definitely, not days or weeks) to allow nitrogen atoms to diffuse to each other through a tightly packed diamond lattice. Such a long HPHT treatment period makes the whole process not feasible. It''s less costly to grow 2a diamonds, instead.

Alexei,
There have been reports of HPHT treatment (in a press, ~ 30+ years ago!) of synthetic diamond wherein up to 80% conversion of single nitrogen atoms to A centers (pairs) has been claimed, through treatment under appropriate P, T conditions for periods of the order of an hour or so.
I wonder how far the process has been developed further and perfected, since then?
And, surely an additional hour or even a few hours is not that long (or too expensive) when compared to a ~5 day HPHT crystal growth run?
Karl

 

[Alexei Zarakhani]

Date: 6/28/2008 4:09:08 AM
Author: kcherian


There have been reports of HPHT treatment (in a press, ~ 30+ years ago!) of synthetic diamond wherein up to 80% conversion of single nitrogen atoms to A centers (pairs) has been claimed, through treatment under appropriate P, T conditions for periods of the order of an hour or so.

I wonder how far the process has been developed further and perfected, since then?

And, surely an additional hour or even a few hours is not that long (or too expensive) when compared to a ~5 day HPHT crystal growth run?

Karl

Karl,

80% of conversion is not enough. A resulting color won''t be spectacular - at best it will be washed out yellow. What''s a practical use of that? To convert a nice yellow diamond into something which is neither white nor yellow? I, personally, don''t see any benefit of doing that.
It would be a different case should a 100% conversion be attainable. Unfortunately, it''s not the case. Otherwise, all of synthetic diamond growers would be producing nice colorless diamonds.

 

[kcherian]

Date: 6/28/2008 1:02:31 PM
Author: Alexei Zarakhani

Date: 6/28/2008 4:09:08 AM
Author: kcherian


There have been reports of HPHT treatment (in a press, ~ 30+ years ago!) of synthetic diamond wherein up to 80% conversion of single nitrogen atoms to A centers (pairs) has been claimed, through treatment under appropriate P, T conditions for periods of the order of an hour or so.

I wonder how far the process has been developed further and perfected, since then?

And, surely an additional hour or even a few hours is not that long (or too expensive) when compared to a ~5 day HPHT crystal growth run?

Karl

Karl,

80% of conversion is not enough. A resulting color won''t be spectacular - at best it will be washed out yellow. What''s a practical use of that? To convert a nice yellow diamond into something which is neither white nor yellow? I, personally, don''t see any benefit of doing that.
It would be a different case should a 100% conversion be attainable. Unfortunately, it''s not the case. Otherwise, all of synthetic diamond growers would be producing nice colorless diamonds.

Alexei,

~80% conversion of single nitrogen atoms in a diamond lattice to A centers was reported 30+ years ago. One would have thought that in the ensuing 30 year time frame the process would have been developed to achieve 100% conversion?! I won’t bet my pants that “unfortunately it’s not the case” though!
Has this not been achieved yet, or is the technology developed and locked up somewhere? It may perhaps be difficult to know for sure.
But is there a scientific reason(s) why 100% conversion would not be attainable? Also, I believe there would be ways to reduce the risk of loosing a stone by doing a HPHT treatment on a synthetic rough… Well, I guess these would be worthy challenges for your R&D personnel.

Karl

 

[Alexei Zarakhani]

Date: 6/28/2008 3:40:48 PM
Author: kcherian

Has this not been achieved yet, or is the technology developed and locked up somewhere? It may perhaps be difficult to know for sure.

The only company I could think of is the DTC''s Gem Defense Unit. They thoroughly researched HPHT treatment of both natural and lab-grown diamonds. If they developed anything and locked it, I don''t know.

But is there a scientific reason(s) why 100% conversion would not be attainable?

Theoretically, it''s possible to reach 100% of conversion but only over a lengthy period of time. As such, it''s not feasible.

 

[kcherian]

Date: 6/30/2008 3:12:11 PM
Author: Alexei Zarakhani

Date: 6/28/2008 3:40:48 PM
Author: kcherian

Has this not been achieved yet, or is the technology developed and locked up somewhere? It may perhaps be difficult to know for sure.

The only company I could think of is the DTC''s Gem Defense Unit. They thoroughly researched HPHT treatment of both natural and lab-grown diamonds. If they developed anything and locked it, I don''t know.

Even if someone may have locked up the technology, I guess it would be of much interest to companies like yours and Clark’s to reinvestigate the process, or develop novel routes to get similar results?

Date: 6/30/2008 3:12:11 PM
Author: Alexei Zarakhani

Date: 6/28/2008 3:40:48 PM
Author: kcherian

But is there a scientific reason(s) why 100% conversion would not be attainable?

Theoretically, it''s possible to reach 100% of conversion but only over a lengthy period of time. As such, it''s not feasible.

Well, once upon a time it was thought by many that gem diamond synthesis/growth too would not be feasible in the lab as the natural gem diamonds form in nature over a very lengthy period of time!

New solutions may perhaps become possible based on research results in other areas of materials research and being able to put two and two together.....for example, consider the reported results on multiplexed & pulsed high power laser irradiation leading to solid state decrystallzation of diamond due to atomic displacements in the diamond lattice.....and it has recently been found that diffusion of impurities/dopants in some crystal lattices may be accelerated when processed in certain electromagnetc fields..... just some food for thought!

By the way, I would appreciate knowing the views of experts like you and Clark on my queries on another thread, on 1) diamond growth from non-metallic solvent catalysts and 2) surface microstructures of HPHT / BARS gem diamonds and comparison with naturals.....

Karl

 

[Clark McEwen]

Date: 7/1/2008 2:44:40 AM
Author: kcherian

Date: 6/30/2008 3:12:11 PM

Author: Alexei Zarakhani

Date: 6/28/2008 3:40:48 PM

Author: kcherian

Has this not been achieved yet, or is the technology developed and locked up somewhere? It may perhaps be difficult to know for sure.

The only company I could think of is the DTC''s Gem Defense Unit. They thoroughly researched HPHT treatment of both natural and lab-grown diamonds. If they developed anything and locked it, I don''t know.

Even if someone may have locked up the technology, I guess it would be of much interest to companies like yours and Clark’s to reinvestigate the process, or develop novel routes to get similar results?

Date: 6/30/2008 3:12:11 PM

Author: Alexei Zarakhani

Date: 6/28/2008 3:40:48 PM

Author: kcherian

But is there a scientific reason(s) why 100% conversion would not be attainable?

Theoretically, it''s possible to reach 100% of conversion but only over a lengthy period of time. As such, it''s not feasible.

Well, once upon a time it was thought by many that gem diamond synthesis/growth too would not be feasible in the lab as the natural gem diamonds form in nature over a very lengthy period of time!

New solutions may perhaps become possible based on research results in other areas of materials research and being able to put two and two together.....for example, consider the reported results on multiplexed & pulsed high power laser irradiation leading to solid state decrystallzation of diamond due to atomic displacements in the diamond lattice.....and it has recently been found that diffusion of impurities/dopants in some crystal lattices may be accelerated when processed in certain electromagnetc fields..... just some food for thought!

By the way, I would appreciate knowing the views of experts like you and Clark on my queries on another thread, on 1) diamond growth from non-metallic solvent catalysts and 2) surface microstructures of HPHT / BARS gem diamonds and comparison with naturals.....


Karl

Hi Karl,

I would just like to comment on one thing that you said..."natural gem diamonds form in nature over a very lengthy period of time". I''m sure that you are aware of the fact that there are multiple theories on the length of time that it take for carbon to crystallize into diamond in nature. The time ranges from instantaneously to years...nobody knows for sure. We do however know the rate that diamonds crystals grow in a controlled setting, why should we not surmise that crystal growth is crystal growth regardless of where it occurs. I do think that in nature there may be stopping and starting to the growth process whereas in a lab the growth is continuous but the actual crystallization period must be similar.

Cheers,
Clark