ALLVAR Alloy 30 is unique with a negative thermal expansion coefficient of −30 ppm/°C at room temperature, or a 1-meter rod shrinking by 0.003 mm for every degree Celsius rise.

The study also contributes to the growing body of research on negative thermal expansion in anisotropic systems—an area that has historically been under-explored.

The researchers also predict that two other rare-earth metals, thulium and ytterbium, should exhibit Kondo effect-driven NTE, and Mazzone says it would be interesting to see whether the magnitude of ...