As being discussed, the sintering a

As being discussed, the sintering activity is related to the particle size. Thus, the weak densification of the ceramic fabricated with the hydrothermal powders might be due to the low sintering temperature used above (1200℃). Therefore, all the samples were also sintered at higher temperatures. The SEM images of the ceramics sintered at 1220℃ and 1240℃ are shownin Figure 6. The porosity of the hydrothermal ceramic becomes lower with an increase of the sintering temperature (Figs. 6(a, d)). Accordingly, the radial shrinkage ratio increases from around 10.8% to 15.1%. The same phenomenon also occurs for the atmospheric liquid-stateceramic (Figs. 6(b, e)), shrinkage increases from 19.2% to 22.9%. Such findings are consistent with the fact that the sintering process can be promoted by increasing the temperature. Due to the full densification of the hydrolysis ceramic at 1200℃, no improvement is observed at higher temperature. Radial shrinkage ratios remain stable around 27.6%. Furthermore, due to the high sintering activity of the hydrolysis sample, the ceramic is slightly melted at1240℃ (Fig. 6(f)). Due to its spherical nanostructure, the optimal sintering temperature of the hydrolysis ceramic is 40℃ lower than the hydrothermal ceramics.