Rutile-type dense ceramics fabricated by pressureless sintering of Ti1−xRuxO2 powders prepared by sol–gel

Materials in the TiO2–RuO2 system, in different shapes, as thin films, coatings, fine powders, xerogels and aerogels are of great interest for many applications, such as energy storage and production systems, solar cells, chemical sensors, electronics, gas separation processes, and industrial electrochemistry. However, a serious drawback in the processing of materials based on RuO2 is the well-established chemical reactivity above ∼700 °C where RuO2 becomes volatile and oxidizes to RuO3/RuO4 gases (in air) or reduces to Ru metal (in a vacuum). For this reason, it is not obvious to attain dense materials in the systems containing Ru. In this study, a novel method has been used to obtain rutile-type Ti1−xRuxO2 (x = 0.05, 0.08 and 0.10) as dense ceramics without the use of the hot-pressing for the sintering step. The relative densities of the materials prepared were higher than 99.0 ρth %). This method combines the sol–gel synthesis, a pressureless fast-firing method (heating and cooling rate of 20 °C min−1) at 1350 °C for 10 min and the use of a buffer during the sintering that provides a RuO3 + RuO4 rich atmosphere.