Unusual thermal conductivity of the negative thermal expansion material, ZrW2O8

In order to investigate the relationship between negative thermal expansion and other thermal properties, the thermal conductivity of the α-phase of ZrW2O8 has been determined from 1.9 to 390 K. In addition, the heat capacity was measured from 1.9 to 300 K. The thermal conductivity of ZrW2O8 is low, glass-like and close to its theoretical minimum value. The phonon–phonon coupling of the highly anharmonic low-frequency modes which are responsible for negative thermal expansion in ZrW2O8 appears to be highly efficient, leading to short phonon mean free paths and exceptionally low thermal conductivity.