Shrinking ceramic

GENERALLY, the laws of physics are very rigid, but this one is found to be rather flexible. It is a well established theory that a material expands on heating. The reason for this thermal expansion is the violent increase registered in the vibrations of atoms or molecules of the material due to extra energy. The more the heat supplied, the more the atoms vibrate and take up more space. Or so it is with most materials.

Now, scientists at Oregon State University and Corvallis and Brookhaven National Laboratory, Upton, both in the us, have discovered a material which behaves in the opposite manner; it shrinks on heating! The wonder material is a ceramic called zirconium tungstate, a blend of tungsten, oxygen and zirconium (ZrW 208). The ceramic when heated from about 0.3 Kelvin to 1,050 Kelvin (the decomposition temperature), shows a negative thermal expansion. What is more, the negative thermal expansion behaviour is isotropic- the same in all directions. Before this work, a few other materials were known to show shrinkage when heated. Cordierite, another ceramic shrinks when heated from ZO