The grant of ₹242 crore out of the Budget to the Indian Institute of Technology, Madras, has gingered-up activity on research into lab-grown diamonds (LGD) at the institute, which now intends to set up a National Centre for Lab-Grown Diamonds.

The Budget has promised to reduce Customs duty on imported ‘seeds’ to grow the diamonds in the lab. IIT-M will primarily concern itself with research into developing technologies for producing seeds in India.

But what are these ‘seeds’?

Natural diamonds are formed over billions of years, around 100 km below the Earth’s crust, under intense pressure and high temperature. Sometimes they are pushed to the surface by the pressure through carrot-shaped weak regions in the Earth, called ‘kimberlite pipes’.

However, the Earth does not burp often — the next may happen after thousands of years. For now, you have to be satisfied with what has been thrown up. Or, simulate the deep-Earth conditions in a lab and cook the diamonds.

The production of these synthetic diamonds starts with ‘seeds’. MS Ramachandra Rao of the Department of Physics, IIT-M, said the two processes of making LGD — high pressure, high temperature and chemical vapor deposition — start with the seeds, which are diamond ‘Type IIa’ crystals, which have no nitrogen or boron impurities.

Only 2 per cent of naturally occurring diamonds are Type IIa and are therefore, very expensive. Only a few companies in the world have the know-how to produce mother seeds, Rao, whose lab will spearhead the research, observed.

There is no known source of high-quality mother seeds or its related technology in India. Currently, it is being imported from other countries to grow good quality diamond.

Research and development are expected to evolve in the next five years such as the proposed National Centre for Lab-Grown Diamond at IIT Madras, in the areas of technology related to diamond seeds in the country which would significantly cut down the import of seeds, Rao told businessline.

In the HPHT method, seeds are exposed along with carbon powder and a catalyst to temperatures of the order of 1,600 degrees Celsius and pressures of about six Giga Pascals.

The CVD method involves breaking down molecules of a carbon-rich gas, such as methane, into carbon and hydrogen atoms in a sealed chamber at sub-atmospheric pressures and temperatures of about 1,100 degrees Celsius. The gas is then deposited on to the seeds to produce a square-shaped diamond crystal.

There is an unending debate as to which process is better. “Both are necessary,” said Rao. Given the energy consumption and necessary equipment, the HPHT method is quite expensive and results in diamonds that are primarily yellowish or brownish yellow in colour along with metallic inclusions.

The CVD process is significantly less expensive because it operates at low pressure and moderate temperatures, requiring less expensive equipment. In CVD, colorless crystals can develop because the vacuum container only has carbon and a small amount of hydrogen. Yellow or blue synthetic diamond crystals can form in the chamber if nitrogen or boron are added.

Lab-grown diamond industries also use HPHT process to treat CVD-grown diamonds for enhancing their quality or imparting different colors such as yellow, yellowish green, green, pink and blue.

LGD beat natural diamonds in purity. “Only 2 per cent of naturally occurring diamonds are defect-free whereas we can grow good quality defect-free diamonds in laboratories, consistently,” said Rao.

Emerging technologies such as high-power electronics, 5G/6G base-station electronics, sensors, magnetometry and quantum computing, need high purity diamond which can only be grown in lab using CVD and HPHT processes.

As for costs, “LGD of less than one carat size is 3-4 times cheaper than natural diamond,” Rao said.

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