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Furuya Metal: uncovering new applications for Iridium

In a recent edition of Tech Metals Insider we reported about the role of iridium crucibles in the manufacturing of sapphire crystals, a process requiring temperatures of around 2,000 degrees celsius. For many years prior, iridium had already been used to produce single crystals used in LEDs.

With a melting point of 2,446 degrees C, pure iridium will perform at the temperatures required, but it will suffer from physical instability and deformation over time, making the process harder to control, and ultimately more expensive. Iridium crucibles are frequently competing with tungsten or tungsten-rhenium crucibles for this reason, although the latter will provide for less homogeneity of the melt produced. This dilemma is, in part, the reason why sapphire glass is not used at a larger scale at present.

One of the world’s leading iridium crucible manufacturers is Furuya Metals with headquarters and production in Japan. Building and expanding on its experience, Furuya just announced the development and successful implementation of an iridium alloy used in so-called “thermo-couples”, devices used for measuring extremely high temperatures.

The new alloy contains 40% rhodium, allowing industrial users to measure temperature in critical applications much more accurately. Steven Hazelbaker, Vice President of Furuya Metal Americas Inc, gave us background information.

“Iridium/Rhodium40 is an alloy manufactured in an arc melting process proprietary to Furuya”, he explained. “The new alloy has already been evaluated for sapphire crystal growth, single crystal growth and rocket engines where it is also used in thermocouples to measure extremely high temperatures”.

The alloy overcomes weaknesses of tungsten-rhenium in oxidation atmospheres and provides for more accuracy in extreme conditions where temperatures reach or exceed 2,000 degrees C. Among the precious metals, iridium has the highest melting point (2,446 degrees C). It will not dissolve in any acid and is five times harder than platinum, in its annealed form.

The combination with rhodium, which by itself melts at just under 2,000 degrees C, enhances resistance to heat and corrosion while providing much superior accuracy compared to non-precious metals.

The benefits? Hazelbaker is confident that “Our new alloy will significantly improve production conditions for sapphire glass, and reduce cost as a result. It will also open up the path for new technologies like SiC substrate annealing, carbon burning, and AlN sintering”.

These effect of these developments will be a transformation of iridium from its past niche existence into the field of mainstream industrial metals, a trend to be observed closely given the relative scarcity of iridium compared to other platinum group metals.

By Bodo Albrecht



Disclaimer: The views expressed in this article are those of the author and may not reflect those of Kitco Metals Inc. The author has made every effort to ensure accuracy of information provided; however, neither Kitco Metals Inc. nor the author can guarantee such accuracy. This article is strictly for informational purposes only. It is not a solicitation to make any exchange in precious metal products, commodities, securities or other financial instruments. Kitco Metals Inc. and the author of this article do not accept culpability for losses and/ or damages arising from the use of this publication.
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