Crystallization of Rare-Earth Phosphate-Borosilicate Glass Composites Synthesized by a One-Step Coprecipitation Method

Abstract

Glass-ceramic composites are heterogeneous materials that have been suggested for use as nuclear waste form materials. A one-step coprecipitation method for synthesizing rare-earth phosphates (REPO4; RE = La or Ce) dispersed in a borosilicate glass (BG) matrix was investigated in this study. The effect of annealing temperature, ceramic loading, and oxidation state of the rare-earth precursor was explored using powder X-ray diffraction, scanning electron microscopy/energy dispersive X-ray spectroscopy, and X-ray absorption near-edge spectroscopy. REPO4 crystallites adopting the monazite structure were observed to form when the annealing temperature was 800–1100 °C in all REPO4–BG composite materials. Lowering the annealing temperature to 700 °C in the LaPO4–BG composite materials caused nm sized LaPO4 crystallites and crystalline SiO2 to form. No changes in the local chemical environment of La or P was observed as a result of the smaller LaPO4 crystallites. CeO2, crystalline SiO2, and Na3Ce­(PO4)2 formed in CePO4–BG composite materials in addition to CePO4 when the annealing temperature was below 1100 °C. CePO4 was not observed to form in CePO4–BG composite materials at low ceramic loadings and when annealed at 700 °C. CePO4 was found to be the favored crystal phase over CeO2 and Na3Ce­(PO4)2 in the CePO4–BG composite materials when the annealing temperature and ceramic loading was increased. The amount of CePO4 present was also found to be dependent on the oxidation state of the Ce precursor.

Review of Rare-Earth Phosphate Materials for Nuclear Waste Sequestration Applications

“…Further, it was also demonstrated that the glass composition can affect the formation of secondary (i.e., unwanted) crystalline phases when lower annealing temperatures are used . An example SEM image and corresponding EDX maps from a glass–ceramic composite material containing CePO 4 crystallites formed by a one-step coprecipitation method are shown in Figure …”

“… 24 An example SEM image and corresponding EDX maps from a glass–ceramic composite material containing CePO 4 crystallites formed by a one-step coprecipitation method are shown in Figure 10 . 25 …”

Research on the progress of Ce3+,Tb3+ co-activated phosphate luminescent materials prepared by hydrothermal method

“…The maximum development and utilization of optical properties of rare earth elements has always been an important topic in the field of luminescent materials [5][6][7]. In this paper, we have studied the achievements of preparing Ce 3+ and Tb 3+ co-activated luminescent materials by hydrothermal method in recent years, and analyzed the influence of the hydrothermal preparation process and influencing factors on the luminescent properties of the luminescent materials, which has important reference significance for the application research and process improvement of the later hydrothermal preparation of Ce 3+ and Tb 3+ co-activated luminescent materials.…”