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Combined Quantitative X-ray Diffraction, Scanning Electron Microscopy, and Transmission Electron Microscopy Investigations of Crystal Evolution in CaO-Al2O3-SiO2-TiO2-ZrO2-Nd2O3-Na2O System TEXT SIZE: A A A
Glass-ceramics, with a specific crystalline phase assembly, can combine the advantages of glass and ceramic and avoid their disadvantages. In this study, both cubic-zirconia and zirconolite-based glass-ceramics were obtained by the crystallization of SiO2-CaO-Al2O3-TiO2-ZrO2-Nd2O3-Na2O glass. Results show that all samples underwent a phase transformation from cubic-zirconia to zirconolite when crystallized at 900, 950, and 1000 degrees C. The size of the cubic-zirconia crystal could be controlled by temperature and dwelling time. Both cubiczirconia and zirconolite crystals/particles show dendrite shapes, but with different dendrite branching. The dendrite cubic-zirconia showed highly oriented growth. Scanning electron microscopy images show that the branches of the cubic-zirconia crystal had a snowflake-like appearance, while those in zirconolite were composed of many individual crystals. Rietveld quantitative analysis revealed that the maximum amount of zirconolite was similar to 19 wt %. A two-stage crystallization method was used to obtain different microstructures of zirconolite-based glass-ceramic. The amount of zirconolite remained approximately 19 wt %, but the individual crystals were smaller and more homogeneously dispersed in the dendrite structure than those obtained from one-stage crystallization. This process-control feature can result in different sizes and morphologies of cubic-zirconia and zirconolite crystals to facilitate the design of glass-ceramic waste forms for nuclear wastes.

Publication name

 CRYSTAL GROWTH & DESIGN, 17 (3):1079-1087; 10.1021/acs.cgd.6b01458 MAR 2017

Author(s)

 Liao, Chang-Zhong; Liu, Chengshuai; Lee, Po-Heng; Stennett, Martin C.; Hyatt, Neil C.; Shih, Kaimin

Corresponding author(s) 

 Shih, Kaimin 
 kshih@hku.hk  
 -Univ Hong Kong, Dept Civil Engn, Pokfulam, Hong Kong, Peoples R China.
 Hyatt, Neil C.
 n.c.hyatt@sheffield.ac.uk
 -Univ Sheffield, Dept Mat Sci & Engn, Immobilisat Sci Lab, Sheffield S1 3JD, S Yorkshire, England.

Author(s) from IGCAS   LIU Chengshuai

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