Dielectric response of silica aerogels

Abstract

The dielectric response of porous silica aerogel prepared by hypercritical drying of gels from hydrolysis of TMOS - Methanol solution have been measured between 1.6 K to 300 K and frequencies between 50 and 105 Hz. The e{open}' value of the porous gels is found practically constant between room temperature and 100K but smaller than of fused silica. A sharp decrease of e{open}' is observed near 35 K and accompanied by a large loss peak (tg ä). A small increase of e{open}' for T < 13 K is attributed to the adsorption of He atoms on the porous superficies.