Fabrication of Al2O3-Nb2O5-LiF-ZrO2 FGMs by SPS method: Microstructural evaluation, dynamic and sintering behaviour

For the first time, alumina functionally graded materials (FGMs) with additions of niobium oxide, lithium fluoride and zirconia were produced by spark plasma sintering (SPS) and their sintering behaviour and dynamic properties were studied aiming to evaluate possibility of their use as ballistic shielding. Six groups of alumina samples with different layer compositions were produced by SPS at 1400 ?C/5min. The samples were characterized by dilatometry, scanning electron microscopy (SEM) and Hopkinson split bar method. The composition with the zirconia addition exhibited lower shrinkage rates at higher temperatures than the groups without zirconia, which promoted small sample shrinkage, resulting in lower density and higher porosity. The dynamic test showed that the alumina FGMs with layer containing LiF had the highest strain and strain rate values, exhibiting that the presence of continuous gradients in the composition positively affects the ceramic properties. Densification, layer change and cracks propagating through the material layers were also analysed by SEM analyses.