T temperature in our study, 940 C, up to 1120 C. SEM micrographs in this area illustrate a microstructure with an just about flat surface, fully packed with grains separated by narrow grain boundaries, which really should be anticipated for dense ceramics (Figure 1a). Remarkably, the grain presented within the literature and discussed in the Introduction.Figure 1. Division of the entire thermal treatment temperature range into three thermal therapy regions, as well as examples of SEM micrographs characterizing every of them: flat microstructure, obtained by thermal remedy at 980 C– Area I (a); microstructure with well-pronounced relief, obtained by thermal treatment at 1200 C–Region II (b); cube-like microstructure, obtained by thermal therapy at 1240 C–Region III (c).Since it follows from the obtained SEM micrographs, the grain size around the surface in Region III definitely increases. It is recognized that increasing sintering temperature induces an increase in the grain size in the whole ceramic . For that reason, when analysing the role of thermal therapy temperature within the grain size distribution around the surface, the effect of thermal treatment temperature on the grain size within the bulk on the ceramics can’t be excluded. In order to compare the influence of higher treatment temperatures on the grain size inside the bulk of your ceramics with all the influence on the surface, a surface layer was grinded off following thermal treatment at a high temperature (1240 C), and another thermal treatment was performed at 980 C, which presumably does not influence microstructure each on the surface and in the bulk in the ceramics, thus helping to reveal the contribution from the higher thermal treatment temperature around the grains inside the bulk in the ceramics. The microstructure obtained for the surface thermally treated only at 980 C was used as a reference. In Figure two, it could be seen that the maximum in the grain size distribution, too as the average grain size, shifted to the larger grain sizes each for the surface thermally treated at 1240 C (Fi.