Solid-state reactive sintering of transparent polycrystalline Nd:YAG ceramics

Transparent polycrystalline Nd:YAG ceramics were fabricated by solid-state reactive sintering a mixture of commercial Al2O3, Y2O3, and Nd2O3 powders. The powders were mixed in methanol and doped with 0.5 wt% tetraethoxysilane (TEOS), dried, and pressed. Pressed samples were sintered from 1700 degrees to 1850 degrees C in vacuum without calcination. Transparent fully dense samples with average grain sizes of similar to 50 mu m were obtained at 1800 degrees C for all Nd2O3 levels studied (0, 1, 3, and 5 at.%). The sintering temperature was little affected by Nd concentration, but SiO2 doping lowered the sintering temperature by similar to 100 degrees C. Abnormal grain growth was frequently observed in samples sintered at 1850 degrees C. The Nd concentration was determined by energy-dispersive spectroscopy to be uniform throughout the samples. The in-line transmittance was > 80% in the 350-900 nm range regardless of the Nd concentration. The best 1 at.% Nd:YAG ceramics (2 mm thick) achieved 84% transmittance, which is equivalent to 0.9 at.% Nd:YAG single crystals grown by the Czochralski method.