Fast sintering of SnO2 nanoparticles after chemical lixiviation

Abstract

Tin oxide based powders without additives present low densification even at high sintering temperatures. Usually, metal cations are introduced as sintering aid, and the densification can be achieved when low temperatures as 1200°C are used, even within a few seconds. In this work, SnO2 based powders were prepared with different amounts of Mg2+ by a polymeric chemical process derived from Pechini's method. The powders were submmited to a lixiviation (washing) process. Both washed and unwashed samples were sintered by fast firing. All unwashed samples presented high initial densification rate, while washed samples showed low rate, but similar to samples containg few amounts of Mg2+. Since sintering is a high-temperature process strongly dependent on surface characteristics, a relationship between additive removal, and the sintering behavior can be established. All powders were characterized by specific surface area. The sintering was studied by means of final density. Surprisingly, samples achieved high densities within few seconds of sintering, and the traditional diffusion theory failed to explain this behavior. The washed sample shown less densification. A hypothesis based on the influence of the additives on the thermodynamic stability of pores was drawn.