Spark plasma sintering (SPS) consolidated ceramic composites from plasma-sprayed metastable Al2TiO5 powder and nano-Al2O3, TiO2, and MgO powders

Spark plasma sintering (SPS) was applied to consolidate the nano-Al2O3, TiO2, MgO powders and plasma-sprayed metastable Al2TiO5 powder. The fully dense ceramics had been prepared successfully. It was found that the starting nano-Al2O3 reacted with nano-TiO2 powder to form the Al2TiO5 phase after SPS consolidation at 1150 °C under a pressure of 63 MPa. The starting plasma-sprayed Al2TiO5 was stable above 1150 °C after SPS under 63 MPa, though in oxidizing atmospheres under the ambient air pressure, the stable temperature range of Al2TiO5 was above 1280 °C. There was a fast decomposition rate for plasma-sprayed Al2TiO5 at 1000 °C during SPS, whereas in oxidizing atmospheres under the ambient air pressure at 1000 °C its decomposition is very slow. The microstructure of powder, applied pressure, and/or SPS characteristics, etc. obviously had an effect on the stable temperature and/or decomposition rate of Al2TiO5. The addition of MgO advanced the formation of Mg0.3Al1.4Ti1.3O5 along with MgAl2O4 in the ceramics prepared both from plasma-sprayed powder and from nano-powder. In comparison with the composition of the ceramics without MgO additive, α-Al2O3, TiO2, and Al2TiO5, the ceramics with MgO additive consisted of only two phases, Mg0.3Al1.4Ti1.3O5 and MgAl2O4 spinel. The small equiaxed MgAl2O4 spinel grains were distributed in a matrix of Mg0.3Al1.4Ti1.3O5 with a large grain size.