An SPS-RS Technique for the Fabrication of SrMoO₄ Powellite Mineral-like Ceramics for ⁹⁰Sr Immobilization

This paper reports a method for the fabrication of mineral-like SrMoO₄ ceramics with a powellite structure, which is promising for the immobilization of the high-energy ⁹⁰Sr radioisotope. The reported method is based on the solid-phase "in situ" interaction between SrO and MoO₃ oxides initiated under spark plasma sintering (SPS) conditions. Dilatometry, XRD, SEM, and EDX methods were used to investigate the consolidation dynamics, phase formation, and structural changes in the reactive powder blend and sintered ceramics. The temperature conditions for SrMoO₄ formation under SPS were determined, yielding ceramics with a relative density of 84.0-96.3%, Vickers microhardness of 157-295 HV, and compressive strength of 54-331 MPa. Ceramic samples demonstrate a low Sr leaching rate of 10^-6 g/cm²·day, indicating a rather high hydrolytic stability and meeting the requirements of GOST R 50926-96 imposed on solid radioactive wastes. The results presented here show a wide range of prospects for the application of ceramic matrixes with the mineral-like composition studied here to radioactive waste processing and radioisotope manufacturing.