Freeze-dried nanometric neodymium-doped YAG powders for transparent ceramics

Nanometric neodymium-doped yttrium aluminium garnet (YAG) has been synthesised from freeze-dried precursors. The products were calcined between 900 °C and 1200 °C under flowing oxygen. Powder morphologies were observed by TEM, SEM and laser granulometer. The oxides had small crystallite size. The best sinterability under vacuum at 1700 °C for 3 h was obtained for precursors with the lowest amount of organic impurities as indicated by IR measurements. Hot isostatic pressing at 1700 °C in 160 MPa of argon was applied to complete the sintering. Under these conditions, Nd:YAG ceramics with very good transmittance were obtained.