Hybrid Sol-Gel and Spark Plasma Sintering to Produce Perovskite-like SrTiO₃ Ceramics for Radioactive Waste Isolation

The paper presents a reliable technology combining sol-gel synthesis and spark plasma sintering (SPS) to obtain SrTiO3 perovskite-type ceramics with excellent physicomechanical properties and hydrolytic stability for the long-term retention of radioactive strontium radionuclides. The Pechini sol-gel method was used to synthesize SrTiO3 powder from Sr(NO3)(2) and TiCl3 (15%) precursors. Ceramic matrix samples were fabricated by SPS in the temperature range of 900-1200 degrees C. The perovskite structure of the synthesized initial SrTiO3 powder was confirmed by X-ray diffraction and thermal analysis results. Scanning electron microscopy revealed agglomeration of the nanoparticles and a pronounced tendency for densification in the sintered compact with increasing sintering temperature. Chemical homogeneity of ceramics was confirmed by energy dispersive X-ray analysis. Physicochemical characteristic studies included density measurement results (3.11-4.80 gcm(-3)), dilatometric dependencies, Vickers microhardness (20-900 HV), and hydrolytic stability (10(-6)-10(-7) gcm(-2)day(-2)), exceeding GOST R 50926-96 and ISO 6961:1982 requirements for solid-state matrices. Ceramic sintered at 1200 degrees C demonstrated the lowest strontium leaching rate of 10(-7) g/cm(2)day, optimal for radioactive waste (RAW) isolation. The proposed approach can be used to fabricate mineral-like forms suitable for RAW handling.