Химическая устойчивость мелкозернистой керамики на основе фосфата Nd0,33Zr2(PO4)3 со структурой коснарита при повышенных температурах

Abstract

Chemical stability of Nd0.33Zr2(PO4)3 fine-grained ceramics, which can be used for immobilization of REE that are part of the HLW was studied. Single-phase Nd0.33Zr2(PO4)3 submicron powders with the structure of the mineral kosnarite were obtained by colloid-chemical synthesis. Powders were obtained by successive annealing at 600, 800, and 900 °C for 6 h at each stage. Ceramics Nd0.33Zr2(PO4)3 has been obtained by Spark Plasma Sintering (SPS) method. The relative density of ceramics was 89.9 %; the average grain size was 5 – 20 μm. The chemical stability of the ceramics in the static mode at 90 °C in distilled water, mineral waters, as well as in acidic media (0.1 M HCl) and alkaline media (0.01 M NaOH) was studied. Ceramics have high hydrolytic stability. The influence of the contact medium on the rate leaching and mechanism of Nd leaching from the surface of Nd0.33Zr2(PO4)3 fine-grained ceramic samples has been studied. The de Groot-van der Sloot model was used to analyze the obtained time dependences of the leaching rate Ri. Nd leaching in acidic medium occurs due to dissociation of Nd from the ceramic surface, in alkaline medium and mineral water due to diffusion from the inner layers, in distilled water due to the dissolution of the ceramic surface layer.