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Microstructural Evolution from Praseodymium‐Containing Zircon Gels to Pr x ‐ ZrSiO 4 Solid Solutions
Author(s) -
Montoya Noemi,
Alarcón Javier
Publication year - 2012
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2011.05035.x
Subject(s) - monoclinic crystal system , materials science , crystallization , tetragonal crystal system , amorphous solid , crystallography , cubic zirconia , praseodymium , chemical engineering , analytical chemistry (journal) , crystal structure , chemistry , chromatography , metallurgy , ceramic , engineering
Structural evolution and coupled microstructural transformations occurred on annealing mineralizer‐free Pr ‐containing ZrSiO 4 gels up to final praseodymium‐doped zircon yellow pigments are reported. Gels with nominal compositions Pr x ‐ ZrSiO 4 , 0 ≤ x ≤ 0.125, were prepared from mixtures of zirconium and silicon alkoxides and praseodymium acetylacetonate. Crystallization pathway and microstructural changes of thermally treated dried gels were followed by infrared spectroscopy, X‐ray diffraction, field emission scanning and transmission electron microscopies, respectively. Results indicated that the crystallization pathway through the whole process of final Pr x ‐ ZrSiO 4 solid solutions formation displayed three well‐defined steps. The crystallization of tetragonal Pr ‐containing ZrO 2 nanocrystals occurred first, followed by their phase transformation to the monoclinic form. The last step was the reaction between the monoclinic Pr ‐zirconia and the amorphous silica and its kinetics was dependent on the amount of the nominal praseodymium content. The microstructure before the Pr ‐zircon formation consisted of an arrangement of tetragonal‐ or monoclinic Pr ‐containing ZrO 2 particles coated by an amorphous silica layer, with sizes lower than 100 nm and between 200 and 400 nm, respectively. The final Pr x ‐ ZrSiO 4 solid solution products were particles sized in the range between 200 nm and 1 μm. Microstructural changes revealed that the whole formation process to final Pr x ‐ ZrSiO 4 non‐aggregated particles was led by the synthetic procedure used for the preparation of gel precursors.