The metal that does not expand
(Photo: TU Wien)
February 3, 2025 – Most metals expand when their temperature rises. The Eiffel Tower, for example, is around 10 to 15 centimetres taller in summer than in winter due to its thermal expansion. However, this effect is extremely undesirable for many technical applications. For this reason, the search has long been on for materials that always have the same length regardless of the temperature. Invar, for example, an alloy of iron and nickel, is known for its extremely low thermal expansion. How this property can be explained physically, however, was not entirely clear until now.
Now, a collaboration between theoretical researchers at TU Wien (Vienna) and experimentalists at University of Science and Technology Beijing has led to a decisive breakthrough: using complex computer simulations, it has been possible to understand the invar effect in detail and thus develop a so-called pyrochlore magnet – an alloy that has even better thermal expansion properties than invar. Over an extremely wide temperature range of over 400 Kelvins, its length only changes by around one ten-thousandth of one per cent per degree Kelvin.
