High Pressure, Crystal SynthesisPresented by Seth Heerschap

WHY?

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0

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1965 1975 1985 1995 2005 2015

High Pressure synthesis Publication Count

Web of ScienceLuscher et al. (2004)

WHY? – Notable examples▪ 1955 – Diamond (Hall, H. T. Rev. Sci. Instrum. (1960))

▪ 1967 – MgB2 (Filonenko, N. E. et al. Doklady Akademii NaukSSSR. (1967))

▪ 2017 – Metallic Hydrogen(?) (Dias, R. P., Silvera. I. F.. Science (2017))

▪ 2019 – La superhydride (LaH10) (Hemley. R., 2019)

3Somayazulu. M. et al. 2019Silvera. I. et al. 2017

WHAT?

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High Pressure,

synthesis

How do we get B?

Two compounds A and B in non-equilibrium where:

𝐵𝑟𝑒𝑎𝑐𝑡𝑖𝑜𝑛

𝐴

With Gibbs free energy:𝐺𝐵 − 𝐺𝐴 = ΔG

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G

B

A

Δ𝐺 > 0

How do we get B?

𝑑𝐺 = 𝑉𝑑𝑝 − 𝑆𝑑𝑇

At a set temperature we get,

Δ𝐺 = න0

𝑃

Δ𝑉𝑑𝑃

Since Δ𝑉 depends on pressure, Δ𝐺 can become negative by increasing the pressure!

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G

B

A

Δ𝐺 > 0

A

B

Δ𝐺 < 0𝑃 increase

Add pressure!!!

An example

7F. Marsolat et al (2014)

𝚫𝑮 = 𝟎

Pressure Assemblies: Piston-cylinder▪ Uniaxial

▪ Accurate

▪ Large volume

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Pressure up to 4 GPa (40 kBar or

~40,000 atm)

Belt Press (GE 1960)

Gia

rdin

i et al. 1

962

A) Pyrophyllite tube, B) Graphite heater, C) Mo disks

sandwiching mica ring; D) Steel cover; E) Pyrophyllite gasket.

F) Polymer gasket

Piston Cylinder –growth of GaN▪ Heated using a Pt-Rh furnace

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(1) High pressure apparatus capillary, (2) screw, (3) plug, (4)

3rd stage of high pressure chamber, (5) cooling system, (6)

piston, (7) gas cleaner, (8) press piston, (9) 2nd stage of

compression, (10) 1st stage of compression, (11) bottled gas,

(12) 4th stage of high pressure chamber.

J. K

arp

inskiet a

l. / Hig

h p

ressure

vapor g

row

th o

f GaN

Pressure Assemblies: Multi-anvil (MAA)

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Pressure up to 95 GPa

▪ Higher pressure

▪ Can be heated by cylindrical graphite furnace

Giardini et al. 1962 Gemological Institute of

America

Pressure Assemblies: Multi-anvil (MAA)

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The furnace

Furnace

Pressure Assemblies: Diamond-anvil (DAC)

12Pressure up to 640 GPa

serc.carleton.edu

serc.carleton.edu

▪ Highest pressure

▪ Laser heated

Pressure Assemblies: Shockwave

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Pressure up to >500 GPa

▪ Fastest crystal growths□ Can produce micron sized

crystals, one of the first methods to produce diamond

Giardini et al. 1962

Pressure Assemblies: Material

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▪ Tungsten Carbine (WC) – up to 31 GPa in multi-anvil press (Katsura et al 2004).

▪ Sintered Diamond (SD): Up to 95 GPa (Yamazaki et al. 2011)

▪ Single Crystal Diamonds (SCD): up to 640 GPa (L. Dubrovinsky(2012)

Theoretical max pressure

S. Zhai, et al. (2011)

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History of synthetic diamonds 📖▪ 1797 – diamonds discovered to be pure carbon

▪ 1893 – Researchers attempt to melt carbon via an electric arc furnace

▪ 1941 – GE and Norton and Carborundum companies attempt synthesis. Heated graphite to 3000C with pressure of 3.5 GPa. WWII interrupted research.

▪ 1954 – First confirmed success using the “belt” press. Capable of 10 GPa at 2000C. Exploiting the Ni-C eutectic. Diamonds were small and unsuitable for gemstones.

▪ 1971 -- First gem-quality stones produced by GE. Yellow and brown due to contamination with nitrogen. Not identical properties to mined diamonds.

▪ 1989 – Commercial production of diamonds using a chemical vapor deposition technique. Diamonds are colorless, small and contain fewer defects than mined.

▪ 2017 – Synthetic diamonds reach 1% of gem market, projected to reach 10% by 2030 as the synthesis of larger and more flawless diamonds become possible (Company reports; Citi)

Britannica

Thank you!Questions?

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