NOVELTY - Zirconium oxychloride is dissolved in water and heated. Thulium oxide, urea, and acrylic ester are added and dissolved, and hot-water precipitation is carried out to obtain zirconium hydroxide and thulium hydroxide mixed colloid. The colloid is washed and spray-dried to obtain a dry powder. The dry powder is calcined and mixed with water. A dispersing agent and polyethylene glycol 2000 are added, ball-milled, and spray-granulated to obtain grains of thulium-zirconium ceramic nanopowder comprising thulium oxide (7-38%) and zirconium oxide (62-93%).    USE - Hydrothermal precipitation of thulium-zirconium ceramic nanopowder used for electrolyte materials of solid fuel cells.    ADVANTAGE - The method enables preparation of spherical or near-spherical thulium-zirconium ceramic nanopowder having excellent fluidity.    DETAILED DESCRIPTION - Zirconium oxychloride is dissolved in water in a pot made of polypropylene material and heated to 60-80 degrees C. Thulium oxide is added and dissolved, followed by addition and dissolution of urea. The solution is added to a ceramic reaction pot using a PVC plastic pipe at 1 MPa and 150 degrees C. An acrylic ester is added and hot-water precipitation is carried out to obtain zirconium hydroxide and thulium hydroxide mixed colloid. The colloid is taken out centrifugally, washed 3-5 times using 1 mol/l of silver nitrate solution for confirming that there is no chloride ion. The colloid paste is put into a spray dryer using a membrane pump and dried to obtain a dry powder. The dry powder is transferred to a pipe type rotary calcining furnace, laid on a quartz glass pipe wall with an inclined angle, and calcined at 600-800 degrees C. The dried powder is mixed with water in a ratio of 1:1. A dispersing agent and polyethylene glycol 2000 are added and high-speed ball-milled for 2-3 hours. The milled slurry is transferred to a spray granulator at an inlet temperature of 200-250 degrees C and an outlet temperature of 100-150 degrees C, for forming grains of thulium-zirconium ceramic nanopowder comprising thulium oxide (7-38%) and zirconium oxide (62-93%). The ceramic powder has a crystal size of 5-12 nm and compact spherical structure.