Zirconia-tungsten composites: synthesis and characterisation for differentmetal volume fractions

Zirconia-tungsten composites have been obtained by the densification of cer amic-metal powders. The influence of the sintering conditions and the metal volume fraction on the morphology, the porosity, the linear shrinkage, the microhardness and on the linear expansion coefficient has been evidenced. Using a general effective medium equation to fit the electrical resistivity of the composites (1400 degreesC-3h) a percolation threshold of 0.26 has b een found. The distribution functions of relaxation times obtained from imp edance spectroscopy measurements show that the higher is the thermal treatm ent the sharper are the peaks and the lower is the relaxation time tau (p). The intragrain zirconia ionic conductivity is improved for high tungsten v olume fractions below the percolation threshold. (C) 2001 Kluwer Academic P ublishers.