Effect of SiO ₂ on Densification and Microstructure Development in Nd:YAG Transparent Ceramics

Abstract

This paper examines the influence of SiO 2 doping on densification and microstructure evolution in Nd 3 x Y 3−3 x Al 5 O 12 (Nd:YAG) ceramics. Nd:YAG powders were doped with 0.035–0.28 wt% SiO 2 and vacuum sintered between 1484° and 1750°C. 29 Si magic‐angle spinning nuclear magnetic resonance showed that Si 4+ substitutes onto tetrahedrally coordinated Al 3+ sites. High‐resolution transmission electron microscopy showed no grain boundary second phases for all silica levels in samples sintered at 1600°–1750°C. Coarsening was limited by a solute drag mechanism as suggested by cubic grain growth kinetics and transmission electron microscopy energy‐dispersive X‐ray spectroscopy observations of increased Nd 3+ concentration near grain boundaries. Increasing SiO 2 content increased both densification and grain growth rate and led to increasingly coarsening‐dominated sintering trajectories. Fine‐grained (<3 μm), highly transparent (>82% real in‐line transmission) ceramics were produced by sintering 0.035 wt% SiO 2 ‐doped ceramics at 1750°C for 8 h. Coarse‐grained (18 μm), transparent samples were obtained with 0.28 wt% SiO 2 ‐doped Nd:YAG when sintered at 1600°C for 8 h.