Thermal conductivity of highly porous zirconia

Highly porous zirconia ceramic with nanometric sized grains was prepared from an 8 mol% yttria stabilised zirconia suspension mixed with a commercial latex. The pore volume fraction was varied from 45 to 75% by adjusting the thermal treatment between 750 and 1100 degrees C. Observations of the microstructure reveal variation in pore shape and size. Mean grain sizes are less than 70nm. Mercury porosimetry measurements reveal a bimodal pore size distribution. Thermal diffusivity measurements were made with the laser flash technique in order to determine the thermal conductivity at room temperature. The thermal conductivity approaches a lower limit of 0.1 W m(-1) K-1. Experimental results were shown to agree closely with predictions made with Landauer's effective medium expression for a two-phase system. The agreement was improved even further by taking into account the interfacial thermal resistance of the grain boundaries and the pore size distribution. (c) 2005 Elsevier Ltd. All rights reserved.