On the precipitation of coherent spinel nanoparticles in Ti-doped MgO

✍ Scribed by K.C. Yang; P. Shen

• Publisher: Elsevier Science
• Year: 2005
• Tongue: English
• Weight: 968 KB
• Volume: 178
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1016/j.jssc.2004.12.019

✦ Synopsis

The Mg 2 TiO 4 /MgO composites prepared by reactive sintering of MgO and TiO 2 powders (9:1 molar ratio) at 1600 1C and then air-cooled or further aged at 900 1C were studied by X-ray diffraction and analytical electron microscopy in order to characterize the microstructures and formation mechanism of nanosized Mg 2 TiO 4 spinel precipitated from Ti-doped MgO. Expulsion of Ti 4+ during cooling caused the formation of (001)-specific Guinier-Preston zone under the influence of thermal/sintering stress and then the spinel precipitates, which were about 30 nm in size and nearly spherical with {111} and {100} facets to minimize coherency strain energy and surface energy. Secondary nanosized spinel was precipitated and became site saturated during aging at 900 1C, leaving a precipitate-free zone at the grain boundaries of Ti-doped MgO. The intergranular spinel became progressively Ti-richer upon aging at 900 1C and showed /110S-specific diffuse scatter intensity likely due to short-range ordering and/or onset decomposition.