THERMAL-CONDUCTIVITY AND HEAT-CAPACITY STUDY OF A DENSIFIED A-SIO2

The thermal conductivity and the specific heat of a densified fused silica a-SiO2 that has a density about 20% higher than that of undensified one from 15 K to room temperatures were measured. The thermal conductivity shows a plateau at temperatures up to 60 K, and the magnitude of the plateau is higher than that of undensified a-SiO2. Above 60 K, the thermal conductivity increases approximately linearly with temperature. A simple analysis of the thermal conductivity data measured on two different portions of the sample reveals that the thermal conductivity plateau is most strongly affected by the densification. Specific heat at temperatures below 60 K is slightly smaller than that of undensified a-SiO2, and gradually approaches the value of undensified a-SiO2 at higher temperatures.