The effect of silica doping on neodymium diffusion in yttrium aluminum garnet ceramics: implications for sintering mechanisms
✍ Scribed by R. Boulesteix; A. Maître; J.-F. Baumard; Y. Rabinovitch; C. Sallé; S. Weber; M. Kilo
- Publisher
- Elsevier Science
- Year
- 2009
- Tongue
- English
- Weight
- 960 KB
- Volume
- 29
- Category
- Article
- ISSN
- 0955-2219
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✦ Synopsis
The Nd 3+ cation diffusion into transparent polycrystalline YAG (Y 3 Al 5 O 12 ) 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 temperatures from 1400 to 1600 • C. Bulk and grain boundary neodymium diffusion coefficients were measured by secondary ion mass spectrometry. The experimental results show that silica addition increases the diffusivity of Nd 3+ 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 in the temperature range 1450-1550 • C. 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 600 kJ mol -1 . 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 a temperature lower than 1500 • C, with an activation energy of about 880 kJ mol -1 . At higher temperature, it seems to be limited by the ionic diffusion through the intergranular liquid phase, with an activation energy of 250 kJ mol -1 .