Fig. 1. XRD diffraction spectra of samples from room temperature to 1 100 ℃ sintering(a) $\mathrm{A}{\mathrm{l}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ nanoceramics, (b) $\mathrm{C}\mathrm{a}\mathrm{O}/\mathrm{A}{\mathrm{l}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ nanoceramics

Fig. 2. XRD diffraction spectra of samples from 920 ℃ to 1 000 ℃ sintering(a) $\mathrm{A}{\mathrm{l}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ nanoceramics, (b) $\mathrm{C}\mathrm{a}\mathrm{O}/\mathrm{A}{\mathrm{l}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ nanoceramics

Fig. 3. SEM photographs of $\mathrm{A}{\mathrm{l}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ nanoceramics at different sintering temperature(a) Room temperature, (b) 700 ℃, (c) 900 ℃, (d) 1 100 ℃

Fig. 4. SEM photographs of $\mathrm{C}\mathrm{a}\mathrm{O}/\mathrm{A}{\mathrm{l}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ nanoceramics cross-sectional morphology at different sintering temperature(a) Room temperature, (b) 700 ℃, (c) 900 ℃, (d) 1 100 ℃

Fig. 5. SEM photographs of the second phase in $\mathrm{C}\mathrm{a}\mathrm{O}/\mathrm{A}{\mathrm{l}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ nanoceramics cross-sectional morphology (a) 900 ℃ 2 000× magnification, (b) 900 ℃ 20 000× magnification, (c) 1 100 ℃ 2 000× magnification, (d) 1 100 ℃ 20 000× magnification, (e) EDS result at second phase (big rectangle), (f) EDS result at base (small rectangle)

Fig. 6. Average particle size of $\mathrm{C}\mathrm{a}\mathrm{O}/\mathrm{A}{\mathrm{l}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ nanoceramics and $\mathrm{A}{\mathrm{l}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ nanoceramics changes with temperature

Fig. 7. The length and strength of positron lifetimes and strength of nanoceramics at different temperatures CaO/Al₂O₃ nanoceramics: (a) ${\tau }_{\mathrm{1}}$,${\tau }_{\mathrm{2}}$, (b) I₁, I₂, (c) ${\tau }_{\mathrm{3}}$, (d) I₃, (e) ${\tau }_{\mathrm{a}\mathrm{v}\mathrm{g}}$; Al₂O₃ nanoceramics: (f) ${\tau }_{\mathrm{1}}$, ${\tau }_{\mathrm{2}}$, (g) I₁, I₂, (h) ${\tau }_{\mathrm{3}}$, (i) I₃, (j) ${\tau }_{\mathrm{a}\mathrm{v}\mathrm{g}}$