Influence of Temperature and Pressure on the Densification, Microstructure, and Electrical Properties of the Dual-Phase System Y2O3-Doped ZrO2 and RuO2

Dual-phase nanocomposite powders of 3Y-TZP (tetragonal-ZrO 2 doped with 3 mol % Y 2 O 3 ) and RuO 2 have been prepared and densified into compacts. The electrical conductivity of the densified compacts was correlated with the microstructure. Variations in the synthesis method and powder composition influenced the densification and resulting microstructure of the composites. Densification of the composites was sensitive to changes in experimental temperature/pressure conditions. Sinterforging the material in the range 1150−1250 °C and 50−100 MPa pressure resulted in dense (>95%) composites. The microstructure of the sinterforged materials revealed that macroscopic phase separation had occurred as a result of the aerial oxidation of RuO 2 species above ≈700 °C. Because of the volatilization of RuO 2, the pores in the pressed powder compact became filled with large ruthenia grains during densification. The microstructure thus reflected the agglomerate structure of the starting powder. The “inhomogeneous” microstructure led to high electrical conductivity in the material. The electrical conductivity of the dense composites was measured by the four-point technique and conductivity values on the order of 1−6 × 10 3 S cm - 1 were obtained. High electrical conductivity (4.4 × 10 3 S cm - 1 ) could be obtained, even at relatively low RuO 2 contents of 15 mol %.