The TEM images of the CSP-CS specim

The TEM images of the CSP-CS specimens conventionally sintered at 600 °C for 2 h are presented in Fig. 7. While the 0YN specimen displays a microstructure composed of Y2O3 particles (Fig. 7a), the 1YN and 20YN specimens display the presence of very small sized Y2O3 particles between the larger Y2O3 particles (Fig. 7b and c). It was concluded that the second phases were transformed into very fine Y2O3 and located between the Y2O3 particles during sintering above 600 °C. In particular, the voids between the Y2O3 particles in the 20YN sample (Fig. 7c) were well filled with very fine Y2O3 particles. Hence, as the amount of added yttrium nitrate increased, the amount of second phase increased and the amount of transformed finesized Y2O3 also increased.