(Bi 2 O 3 ) 0.75 (Dy 2 O 3 ) 0.25 nanopowder was prepared by reverse chemical titration co-precipitation method. The reaction mechanism during the precipitation process was discussed by thermodynamic analysis. Thermal decomposition behavior of the precursor was investigated using X-ray diffractometry and TG–MS analysis. The precursor was calcined at 500°C for 3h to obtain (Bi 2 O 3 ) 0.75 (Dy 2 O 3 ) 0.25 nanopowder. Using the nanopowder, pellets with relative density higher than 94% were obtained at 700°C for 2h by pressureless sintering, and the grains remained at the nano-scale with size of 72nm.