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Discovery
Hafnium was discovered in 1923 as one of the last stable elements in the periodic table. As early as 1914, the British physicist Henry Moseley had predicted on the basis of his law of X-ray spectra that a previously unknown element with atomic number 72 must exist between lutetium and tantalum. Initially, another lanthanide like lutetium was suspected. Lanthanides are a group of 15 chemically very similar elements in the periodic table that follow the eponymous lanthanum. Together with scandium and yttrium, they are referred to as rare earth elements.
George de Hevesy, AI presentation
Dirk Coster, AI presentation
Despite extensive research, however, the suspected element 72 could not be found in the corresponding minerals. In 1922, the Danish physicist Niels Bohr predicted that it must be more similar to zirconium. The Dutch physicist Dirk Coster and the Hungarian chemist George de Hevesy were able to confirm this the following year: Using X-ray spectroscopy, they identified hafnium in a zirconium mineral. The element was named after the place of its discovery, Copenhagen, Hafnia in Latin.
Extraction
The industrial extraction of hafnium developed in the shadow of zirconium production. The metal is produced exclusively as a by-product in the processing of zircon - a mineral that contains both zirconium and hafnium. Hafnium was technically developed from the 1940s and industrially relevant quantities were available from the 1950s. Nuclear energy was an important driver in this process: Hafnium had to be almost completely removed for the use of zirconium in reactors, as it impaired the desired material properties.
The most important locations for separation and further processing were and are located in a few countries, including France, the USA and China. The raw material base comes from zircon sands, which are primarily extracted in Australia, South Africa, Indonesia and other countries with deposits of heavy mineral sands.
Historical areas of application
Bragg ionization spectrometer. In 1913/14, Henry Moseley used an identical device to measure the characteristic X-ray radiation of over 30 elements - thus laying the physical foundation for the concept of the atomic number.
Image: CCBY4.0 Wellcome Collection
As hafnium was only discovered in 1923 and was difficult to access in its pure form for the first few decades, industrial applications developed relatively late. It was only with the expansion of nuclear technology in the 1940s and 1950s that hafnium gained in importance. On the one hand, it had to be laboriously separated from zirconium, which was used for fuel element cladding - unlike zirconium, hafnium absorbs neutrons particularly well instead of allowing them to pass through. On the other hand, it was precisely this property that was used as a material in control rods to control the chain reaction in reactors. This is still a central field of application for hafnium today.
In the decades that followed, further areas of application emerged, in particular high-temperature resistant alloys such as the so-called superalloys for turbines. There are also special metallurgical and electrical applications. Since the 2000s, hafnium has also played an important role in microelectronics, particularly in the form of hafnium oxide as a high-k dielectric in modern semiconductor components.
Industrial use therefore remains concentrated on a few specialized niche applications to this day.