Sintering and grain growth in SiO2 doped Nd:YAG

The influences of silicate doping on the densification and microstructure of Nd:YAG was investigated. Pure YAG, and YAG, Nd:YAG (1-9 at% Nd), all doped with 0.14 wt% SiO2, were prepared by ball milling Al2O3, Y2O3, Nd2O3 and TEOS. Pressed specimens were sintered at temperatures up to 1850 C for up to 16 h in vacuum. The pure YAG sintered by solid state diffusion, achieving near theoretical density by 1700 C. The activation energy for coarsening was greater than that for densification, indicating that little or no grain growth should occur so long as no thermodynamically stable pores were present. The SiO2-doped specimens densified by liquid phase sintering, achieving full density at 100 C < YAG. SiO2-doped Nd:YAG exhibited enhanced sintering and grain growth at low temperatures, compared with SiO2-doped YAG, attributed to increased liquid phase content. At temperatures > 1700 C, Nd:YAG of high Nd content had a smaller grain size than Nd:YAG of low Nd content, attributed to solute drag effects. 32 refs.