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

The thermal conductivity and the specific heat of a densified fused si lica a-SiO2 that has a density about 20% higher than that of undensifi ed one from 15 K to room temperatures were measured. The thermal condu ctivity 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 tempera ture. A simple analysis of the thermal conductivity data measured on t wo different portions of the sample reveals that the thermal conductiv ity plateau is most strongly affected by the densification. Specific h eat at temperatures below 60 K is slightly smaller than that of undens ified a-SiO2, and gradually approaches the value of undensified a-SiO2 at higher temperatures.