Transparent YAG obtained by spark plasma sintering of co-precipitated powder. Influence of dispersion route and sintering parameters on optical and microstructural characteristics

A fine-grained (330nm) yttrium aluminium garnet (YAG) ceramic, presenting a non-negligible transparency (66% RIT at 600nm), was obtained by spark plasma sintering. The YAG powder was manufactured by co-precipitation, starting from a yttrium and aluminium chlorides solution. A soft precursor was obtained, whose phase evolution was studied by X-ray diffraction. Calcined powders were dispersed by either ball milling or by ultrasonication and then subjected to spark plasma sintering at several temperatures (1200–1400°C) and for a reduced time (15min). It is shown that the dispersion method plays a key role in enhancing the optical characteristics of YAG ceramics, in order to obtain a material with a small grain size, transparent in both the visible and the infrared range.