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 Al 2 O 3 , Y 2 O 3 , and Nd 2 O 3 powders. The powders were mixed in methanol and doped with 0.5 wt% tetraethoxysilane (TEOS), dried, and pressed. Pressed samples were sintered from 1700° to 1850°C in vacuum without calcination. Transparent fully dense samples with average grain sizes of ∼50 μm were obtained at 1800°C for all Nd 2 O 3 levels studied (0, 1, 3, and 5 at.%). The sintering temperature was little affected by Nd concentration, but SiO 2 doping lowered the sintering temperature by ∼100°C. Abnormal grain growth was frequently observed in samples sintered at 1850°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.