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Newsletter "SEI NEWS" 2012

Home > Company Information > SEI WORLD > Back number > Vol.415

[Newsletter "SEI NEWS" Vol.415]

Synthetic Single Crystal Diamond "SUMICRYSTAL"

Diamond is the hardest natural material on earth. Owing to its superior hardness, strength, thermal conductivity, electrical characteristics, and other physical properties, diamond is called the "king of materials."

Successful synthesis of world's largest single crystal diamond

Sumitomo Electric makes its major products ? electric wires ? by drawing (or reducing the diameter of) wire rods with dies. Around 1970, the Company noticed that diamond could be used as a die material to replace cemented carbide in use at the time, and so began developing a synthetic diamond. In 1982, the Company succeeded in synthesizing a 1.2 -carat single crystal diamond that was then one of the world’s largest synthetic diamonds. This diamond was registered in the 1984 Guinness Book of World Records as the world's largest synthetic diamond. At the time, synthetic diamond crystals contained various impurities and assumed a yellow color. At present, approximately 10 -carat high-purity, clear and colorless, high-quality diamond crystals can be synthesized (which are currently the world's highest class of high-purity diamond crystals).



Certificate of registration in the 1984 Guinness Book of World Records


For what purposes are synthetic diamonds used?

Diamond knives used for slicing extremely thin test specimens

Owing to their superior hardness, physical properties, synthesis-specific crystallizability, quality stability, and other features, synthetic diamonds are widely used to cut non-ferrous metals, ceramics and semiconductor crystals, to mirror-finish optical lens molds, to draw extremely thin electric wires for electronic devices, to maintain industrial grinders, and for various other purposes.

We continued our efforts to further improve the purity and size of synthetic diamonds, and succeeded around 2000 in synthesizing a high-purity, clear and colorless, 1 cm diameter (8 -carat) diamond crystal. This success increased the number of synthetic diamonds used for cutting tools and also expanded their use to optical parts, window materials, dispersive elements, and other non-tool products. We expect that the use of synthetic diamonds will dramatically expand in the electronics and life science fields.

Hitoshi Sumiya Industrial Materials and Process Technology R&D Labs.

■ Interview with engineer in charge
What motivated you to be involved in developing synthetic diamonds?

Although Sumitomo Electric was the world's first to mass-produce approximately 1 -carat synthetic single-crystal diamonds, they were yellow due to impurities and their size was 5 mm or less. Believing that the development and expanded use of a larger size, higher-purity, clearer and colorless diamond crystal would contribute to the progress of industrial technology, I began upgrading synthesis technology. For 15 years now, I have devoted myself to technology development to increase the size, enhance the purity, and improve the crystallizability of synthetic diamonds. Today, we can synthesize 1 cm diameter or larger diamond crystals with higher quality than that of natural diamonds.

Tell the story behind the development and the difficulties you encountered.

We spent 15 long years to improve an approximately 5 mm, 1 -carat yellow crystal into a high-purity, clear and colorless crystal of more than 1 cm (8 -carat). During the course of development, we confronted one problem after another. We were forced to repeat over and over like playing Whack-A-Mole.

When I entered the Company, I never dreamed that we would be able to synthesize such large, high-quality diamonds. What I have learned from this development project is that technical development with passion and conviction will finally accomplish the impossible.

■ Product data
Start of production 1985 (synthesis success: 1982)
Production method High-temperature/high-pressure synthesis with ultrahigh-pressure/high-temperature pressing machine
Use Cutting tools, wire drawing dies, dressers (maintenance tools for industrial grinders), infrared optical materials, ultra-precision knives, ultrahigh pressure anvils, etc.

- SUMICRYSTAL is a trademark or registered trade name of Sumitomo Electric Industries, Ltd.

2012 Index
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