Structural Features of Phosphate and Sulfate Modified Zirconia Prepared by Sol–Gel Route |
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Authors: | C. A. Kawaguti L. A. Chiavacci S. H. Pulcinelli C. V. Santilli V. Briois |
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Affiliation: | (1) Instituto de Química-UNESP, P.O. Box 355, 14801-970 Araraquara, SP, Brazil;(2) LURE, Université Paris-Sud, BP34, 91898 Orsay Cedex, France |
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Abstract: | This paper describes the effect of sulfate, phosphate and nitrate complexing ligands on the structural features of amorphous xerogels and on the crystallization of metastable zirconia phases during the xerogel-ceramic conversion. Powdered samples were prepared by a sol–gel route using zirconyl chloride precursors chemically modified by complexing ligands. The structural evolution of ZrO2 phases as function of firing temperature was analyzed by XRPD, EXAFS and 31P NMR/MAS. The experimental results show the formation of metastable t-ZrO2 during the low firing temperature of xerogels modified by sulfate or phosphate groups. The martensitic tetragonal-monoclinic transformation occurs during desorption of sulfate groups. The largest temperature interval of stability of metastable tetragonal zirconia was observed for phosphate-modified xerogels. |
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Keywords: | sol– gel process zirconia tetragonal phase |
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