Nanostructuring of dense SnO2 ceramics by Spark Plasma Sintering

Abstract

The spark plasma sintering (SPS) behaviour of pure SnO2 has been studied. Two different SnO2 powders have been studied: a commercial 50–200 nm one and 4–6 nm nanoparticles obtained by precipitation. It has demonstrated that it is not possible to keep pure SnO2 above 1223 K by SPS. Indeed, at 1248 K, SnO appears whereas at higher temperatures, samples are composed by SnO2 and metal Sn. Three different cycles have been developed that allow achieving high densities (≥94%). The study of the grain size shows that when the density increases the grain size increases to reach 60–70 nm for the high density samples. Therefore, SPS can be successfully used to produce dense nanostructured SnO2 ceramics without any sintering agent. Nanostructuring is very efficient to lower thermal conductivity as values as low as 6.59 and 3.99 W m−1.K−1 at 373 and 1000 K respectively, are measured in SPS nanostructured ceramics. Moreover, the transport properties of the dense ceramics are the best reported for undoped SnO2.