Most materials expand when heated, but a few materials do the opposite and contract. Researchers at Nagoya University are now adding to this curious class of materials. A layered ruthenate Ca2RuO4-y exhibits NTE; the sintered-body structure shows colossal NTE when extremely anisotropic thermal expansion of the crystal grains produces deformation, consuming open spaces (voids) on heating; the total volume change related to NTE reaches 6.7% at most,...
