The Nd3+ cation diffusion into transparent polycrystalline YAG was investigated as

a function of temperature and silica content. Thin neodymium oxide layers were

deposited on sintered YAG substrates prior to annealing under air at 1400 to

1600C. Bulk and grain boundary neodymium diffusion coefficients were measured

by secondary ion mass spectrometry. The experimental results showed that silica

addition increases the diffusivity of Nd3+ by a factor 10 whatever the diffusion

path, probably as a result of extrinsic point defects formation, especially rare-earth

vacancies. The experimental diffusion data were used to elucidate the sintering

mechanism of Nd:YAG ceramics at 1450 to 1550C. Firstly, it appeared that the

intermediate stage of solid-state sintering should be controlled by the rare-earth

diffusion along the grain boundary with an activation energy of about 600kJ/mol.

Secondly, grain growth mechanism at the final stage of liquid-phase sintering was

investigated for silica-doped Nd:YAG samples. Thus, the grain growth should be

limited by the reaction at interfaces at below 1500C, with an activation energy of

about 880kJ/mol. At higher temperature, it seems to be limited by the ionic

diffusion through the intergranular liquid phase, with an activation energy of

250kJ/mol.

The Effect of Silica Doping on Neodymium Diffusion in Yttrium Aluminum Garnet

Ceramics: Implications for Sintering Mechanisms. R.Boulesteix, A.Maître,

J.F.Baumard, Y.Rabinovitch, C.Sallé, S.Weber, M.Kilo: Journal of the European

Ceramic Society, 2009, 29[12], 2517-26