Fig. 1. Schematic of IMF kernel preparation by the external gelation process

Fig. 2. Schematic of the device used for IMF kernel preparation by external gelation process

Fig. 3. Transmission electron micrograph of a thorium-zirconium colloid at a 5% Zr molar ratio (a), and under local magnification (b)

Fig. 4. Variations in viscosity with c(NH₄⁺)/c(NO₃^-) under different total metal ion concentrations at a 5% Zr molar ratio

Fig. 5. Variations in viscosity with c(NH₄⁺)/c(NO₃^-) under different reaction temperatures at a 5% Zr molar ratio

Fig. 6. Particle size distribution of Th-Zr sols under different reaction temperatures at a 5% Zr molar ratio

Fig. 7. Particle size distribution of Th-Zr sols under different metal ion concentrations at a 5% Zr molar ratio

Fig. 8. Gelation field diagram of the Th-Zr system at a 5% Zr molar ratio

Fig. 9. Gel spheres at a 5% Zr molar ratio (a), dried microspheres at 200 ℃ (b), and sintered microspheres at 1 350 ℃ (c)

Fig. 10. X-ray image of a sintered Th_xZr_1-xO₂ microsphere at a 5% Zr molar ratio, and metallographic micrograph (inset)

Fig. 11. X-ray diffraction patterns of dried microspheres at a 5% Zr molar ratio (a), calcinated Th_xZr_1-xO₂ microspheres at 650 ℃ (b), sintered Th_xZr_1-xO₂ microspheres at 1 350 ℃ at a 5% Zr molar ratio (c), pure ThO₂ microspheres (d), and pure ZrO₂ microspheres (e)

Fig. 12. Scanning electron microscopic images of the surfaces of Th_xZr_1-xO₂ microspheres at a 5% Zr molar ratio (a), cross-section of a Th_xZr_1-xO₂ microsphere at a 5% Zr molar ratio (b), and cross-section of a pure ThO₂ microsphere sintered at 1 350 ℃ in an air atmosphere (c)

Fig. 13. EDX of Th_xZr_1-xO₂ microspheres at a 5% Zr molar ratio sintered at 1 350 ℃ in an air atmosphere