Applications of Abnormal Grain Growth

Another application of AGG is to obtain single crystals through ceramic processing. Previously, various single crystals, such as ferrites and ferroelectrics, have been obtained by using this technique [57-60]. More importantly, this method has also been used to convert ceramics to solid-state laser single crystals [61-63]. 

The appearance of heavily doped Nd YAG single crystals, with doping concentrations of 2.4, 3.6, and 4.8 %, prepared by the SSCG method is shown in Fig. 8. 8a. A typical reflected (polarized) microscopic image of a near growth interface of a 2.4 % Nd YAG sample is shown in Fig. 8.8b. It was confirmed that grain growth occurred from a seed crystal toward polycrystaUine directions. It 

11 SEM image of interfaee between the polycrystalline and the as-prepared single-crystal part Reproduced with permission from [65]. Copyright 2014, Elsevier 

12 a Photographs of representative YAG Nd and YAG ceramics. Every sample differs from its neighbors by 1 mol% excessive Y2O3 (lY, 2Y) or AI2O3 (lA, 2A), while 0 means stoichiometric Y/ A1 ratio of 3 5. b Porosity (vol.%) as a function of Y/Al ratio for pure and Nd-doped YAG ceramics with different levels of excessive oxides. Reproduced with permission from [62]. Copyright 2013, Elsevier 

13 SHM image of the grown crystal after thermal etching to show the grain boundaries in the ceramics, without boundary being observed in the grown crystal. Reproduced with permission from [62]. Copyright 2013, Elsevier 

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