Mode of action of LiF during the development of YAG transparent ceramics by Spark Plasma Sintering (SPS)

Abstract : The replacement of single crystals like Er3+:Y3Al5O12 (Er:YAG) by polycrystalline ceramics is one of the ways to increase the output power of lasers sources. Although their low thermal conductivity could limit the overheating phenomenon that appears in the bulk material, their use is still limited due to the difficulties to obtain perfect material transparency quality. To meet with this requirement, lithium fluoride (LiF) was pointed out by some authors as an efficient sintering aid because it promotes densification and grain growth and allows the elimination of impurities. However, its mode of action and evolution inside the microstructure are not well known yet. In this work, sintering of YAG ceramics using LiF as a dopant is carried out on a Spark Plasma Sintering (SPS) apparatus. Attention is focused on the understanding of the LiF behavior during the thermal treatment according to optical and structural characterizations of specimens.