Thermal conductivity of binary ceramic composites made of insulating and conducting materials comprising full composition range-Applied to yttria partially stabilized zirconia and molybdenum disilicide

The thermal diffusivity and conductivity of dense and porous binary composites having an insulating and conducting phase were studied across its entire composition range. Experimental evaluation has been performed with MoSi2 particles embedded into yttria partially stabilized zirconia (YPSZ) as prepared by spark plasma sintering (SPS). The thermal diffusivity of the composites was measured with Flash Thermography (FT) and Laser Flash Analysis (LFA) techniques. Subsequently, the thermal conductivity was determined with the measured heat capacity and density of the composites. The actual volume fraction of the conducting phase of the composites was determined with image analysis of X-ray maps recorded with scanning electron microscopy (SEM). The phases present and their density were determined with X-ray diffractometry (XRD) using Rietveld refinement. The thermal diffusivity increases with increasing volume fraction of MoSi2. Porosity reduces the thermal diffusivity, but the effect diminishes with high volume fractions MoSi2. The thermal diffusivity as a function of the MoSi2 volume fraction of the YPSZ composites is captured by modelling, which includes the porosity effect and the high conductivity paths due to the percolation of the conductive phase.

Automated summary

This study investigated the thermal diffusivity and conductivity of dense and porous binary composites with insulating and conducting phases across the entire composition range. Experimental evaluation was performed on MoSi2 particles embedded in YPSZ through spark plasma sintering (SPS). Thermal diffusivity was measured using Flash Thermography (FT) and Laser Flash Analysis (LFA), and the thermal conductivity was determined based on heat capacity and density measurements. The volume fraction of the conducting phase was determined through X-ray map image analysis using scanning electron microscopy (SEM), while X-ray diffractometry (XRD) with Rietveld refinement determined the phases present and their density. The thermal diffusivity increased with increasing volume fraction of MoSi2. Porosity reduced the thermal diffusivity, but the effect diminished with high volume fractions of MoSi2. Modelling captured the thermal diffusivity as a function of MoSi2 volume fraction in YPSZ composites, accounting for porosity and the percolation of the conductive phase.