Self-propagating high-temperature synthesis of barium titanate and subsequent densification by spark plasma sintering (SPS)

摘要

This paper describes the self-propagating high-temperature synthesis (SHS) of perovskitic oxides, specifically BaTiO_3, and their subsequent densification by spark plasma sintering. With the final goal of obtaining dense nanostructured materials, SHS products were mechanically treated at different milling time conditions, before densification. It was found that the grain size of ball milled powders decreases with increasing milling time, this effect being more evident at early stages of milling. Depending upon the ball milling (BM) conditions adopted, crystallite size in the range 15-70 nm was obtained. After milling for 5 h, the resulting powders (20-30 nm) were sintered by SPS, at 700 A, for different periods of time. By properly varying sintering time in the interval 70-140 s, it is possible to obtain products with relative density in the range 66-99 percent, respectively. In particular, grain growth during sintering was found to be limited (below 50 nm) if the electric current is applied for time intervals equal to or less than 100 s. The observed dielectric properties are typical of a nanocrystalline BaTiO_3 ceramic.