1. Electron Irradiation Induced Transformation of (Pb5Ca5)(VO4)6F2 Apatite to CaVO3 Perovskite.
- Author
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Dong, Z. L., White, T. J., Sun, K., Wang, L. M., and Ewing, R. C.
- Subjects
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APATITE , *IRRADIATION , *PEROVSKITE , *TRANSMISSION electron microscopy , *CALCIUM , *PHASE equilibrium - Abstract
Crystallochemical changes of (Pb5Ca5)(VO4)6F2 apatite under electron irradiation were examined by transmission electron microscopy. The apatite, a synthetic analog of vanadinite, was moderately stable towards a less intense 300-keV LaB6 source, while it changed rapidly in structure when exposed to the higher flux of a 200-keV field emission gun. The electron beam induced transformation of vanadinite proceeds sequentially by (i) migration and loss of fluorine, (ii) lead volatilization and conversion to 2-5-nm platelets of a glaserite-type structure, and (iii) the reduction of V5+ to V4+ with the removal of lead and calcium oxide that leads to single-crystal CaVO3 perovskite as the ultimate product. The phase transformations are interpreted based on the crystallographic relations among the CaVO3 perovskite, the (Pb5Ca5)(VO4)6F2 apatite and the glaserite-type structures, and compositional changes under electron irradiation. [ABSTRACT FROM AUTHOR]
- Published
- 2005
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