Unusual thermal conductivity of the negative thermal expansion material, ZrW 2O 8

Abstract

In order to investigate the relationship between negative thermal expansion and other thermal properties, the thermal conductivity of the α-phase of ZrW 2O 8 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 ZrW 2O 8 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 ZrW 2O 8 appears to be highly efficient, leading to short phonon mean free paths and exceptionally low thermal conductivity.