Synthesis and density optimization of fluorite-structured Dy2TiO5 neutron-absorbing powder via a melting–crushing–grading route

Fluorite-structured Dy2TiO5 is an attractive neutron absorber commonly used in bulk form for control rods due to its superior irradiation tolerance and low swelling behavior. However, conventional routes have many disadvantages, such as low purity and low efficiency. In this study, a stabilizer-free process was developed to produce high-purity fluorite Dy2TiO5 powder via ball milling, sintering, melting, rapid quenching, and crushing. During ball milling, Dy2O3 and TiO2 are gradually amorphized as grain size decreases, and no new compounds form regardless of milling parameters. Orthorhombic Dy2TiO5, Dy2Ti2O7, hexagonal Dy2TiO5 and Dy2O3, and low-valent TinO2n-1 are formed depending on the sintering temperatures. After a brief melt at 1900 °C followed by rapid quenching, the hexagonal Dy2TiO5 fully transforms to the high-purity fluorite Dy2TiO5, which is preserved during crushing, with a true density of ∼7.18 to 7.19 g/cm3. Finally, the apparent and tap densities are optimized through particle-size grading and proportioning. The density–fraction relationship is better fitted by a quadratic Scheffé mixture model, consistent with hierarchical void filling, and a predictive formula is proposed. With optimized grading, the powders achieve tap densities of 5.09–5.11 g/cm3 and a porosity of ∼0.288, approaching the practical packing limit.