Microstructure grain size versus density

In Fig. 10.6a-/, the time dependence of the microstructural development of an MgO-doped AI2O3 compact sintered in air at 1600°C is shown. Note that as time progresses, the average grain size increases whereas the average pore size decreases. The corresponding grain size versus density trajectory is shown in Fig. 10.6g which is typical for many ceramics that sinter to full density. 

Figure 11.3. Schematic of microstructure development in terms of a plot of grain size versus density. ...

Figure 9.51 Experimental results for microstructural development in AI2O3 doped with 200 ppm MgO, showing the grain size versus density trajectories for fabrication by hot pressing, conventional sintering, and fast firing. (From Ref. 90.)...

In particular, the most powerful method for studing lattice defects, due to the high sensitivity of positrons to open volume defects such as vacancies, vacancy clusters, voids, dislocations, grain boundaries, etc., is positron annihilation spectroscopy (PAS). A diagram illustrating the applicability of PAS and other techniques as a function of defect size and density versus depth in material is shown in Figure 4.25. Thus, PAS represents a non-local experimental technique that is sensitive to microstructural defects at the atomic scale. A well-established theory of positron annihilation phenomena is currently available. Especially for metallic materials, it is possible to perform ab initio calculations of positron parameters for various defects and atomic arrangements [72,73]. 

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