THERMAL-PROPERTIES OF YTTRIA-STABILIZED ZIRCONIA (YSZ)

The thermal properties and microhardness of yttria-stabilized zirconia ( YSZ) and YSZ doped with 1 Wt% WO3 have been investigated at 300 K. The thermal conductivity lambda of YSZ doped with WO3 has a higher value than without the tungsten doping (lambda(YSZ) = 1.26+/-0.05; lambda(YSZ+WO3) = 1.65+/-0.15 (W/mK)). A similar influence of tungsten addition was found in the case of the microhardness H. H(YSZ+WO3) is 12-15% higher than H(YSZ). The thermal properties in the surface layers and in the bulk of the sample are different. A similar difference was observed in the case of the microhardness H. Doping sharply decreases H in the surface layer,practically down to the level of the bulk value. The results allow the assumption that the doping of YSZ samples with WO3 essentially changes, in a similar way, the structure of surface layer in the ceramic grains as in the single crystals.