According to Rice ceramic materials have a tendency to
The Y2Ti2O7 ceramic discs sintered at different pressures (0–25 MPa) were cut into cross-section to study their porosity by SEM observation. The micrographs in Fig. 2 revealed that the quantity and size of pores inside the sintered ceramics decrease with the increasing of pressure. In the case of ceramic sintered without pressure (Fig. 2a), although some big grains can be seen, the fact that there are abundance of pores between the small grains revealed that pressureless sintering was inadequate to consolidate of the ceramic powder into a dense ceramic body. When the powder was pressed under 5 MPa, the grains were developed to denser structures as shown in Fig. 2b. Although there are some big pores between the grains, it Anastrozole is confirmed that the number of pores was also decreased considerably. When being applied under higher pressures (10, 15 MPa), the sintered ceramic exhibits further dense structure, with less and smaller pores (Fig. 2c and d). The ceramics sintered under 20 and 25 MPa show very dense structure, with very few and small pores (Fig. 2e and f). The relation between sintering pressure and density of ceramics is verified by bulk density measurements, whose results are shown in Fig. 3 and summarized in Table 2. The bulk density of pressureless sintered ceramic (0 MPa) is 89.71% of 4.98 g cm−3 (the theoretical density of Y2Ti2O7), much lower than 95.40% of the pressure sintered ones (5 MPa), reflecting the difference of porous and dense structure shown in Fig. 2. Among pressure sintered ceramics, when the sintering pressure was gradually increased from 5 to 25 MPa, the bulk density also increased, very slightly but steadily, from 95.4% to 98.88%. These data suggests that if we can increase the sintering pressure to be higher, a super full dense ceramic can be obtained. However, because of the limitation of the hot-press system, 25 MPa is the highest pressure can be applied. To further densify the ceramics, other sintering techniques like Hot-isostatic-pressing (HIP) should be used. The densification of Y2Ti2O7 ceramics using HIP will be discussed in later part of spermatogenesis section.