One-pot synthesis of Ln2Sn2O7 pyrochlore and MgAl2O4 spinel by soft chemistry route as potential inert matrix fuel system, and the microstructural analysis

Abstract

MgAl2O4–Ln2Sn2O7 (Ln = Y, La, Nd, Gd and Tb) composite materials with 50–70 vol% of MgAl2O4 as potential inert matrix fuels have been synthesized using a soft chemistry route. X-ray diffraction (XRD), Raman, scanning and transmission electron microscopies (SEM/TEM) are employed to investigate the bulk and micro structures of both ceramic phases. Heat treatment at 1400 °C in air for 24 h leads to the formation of Ln2Sn2O7 pyrochlore and MgAl2O4 spinel which are confirmed by XRD, Raman and selected area electron diffraction (SAED). More importantly, the component in one phase does not affect the crystalline formation of the other. Thermal analysis results show MgAl2O4 crystallizes prior to that of Y2Sn2O7 and the crystallization of Y2Sn2O7 delays due to the presence of MgAl2O4. SEM shows uniformly distributed pyrochlore particles in spinel matrix, especially for the sample in equal volume ratio, with grain sizes being 1–5 μm for both phases. HRTEM and SAED observations confirm that both phases possess a high level of crystallographic perfection at the atomic scale.