Thermal Expansion and Phase Formation of ZrW₂O₈ Aerogels

Abstract

Aerogels with the nominal composition ZrW2O8 have been prepared by pore solvent exchange with liquid CO2 followed by supercritical drying. These aerogels are amorphous and can be tailored to have extremely high surface areas. Thermal expansion is measured for the amorphous aerogel as well as the aerogel post thermal treatment. The cubic phase forms at 900 °C in less than 30 s. The cubic phase prepared this way has a large negative thermal expansion coefficient of −10.5 × 10-6 °C-1 as shown by variable temperature X-ray diffraction.