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The Effect of La 2 O 3 Addition on Sol–Gel Derived Mullitization
Monophasic gel with stoichiometric 3 Al 2 O 3 ·2 SiO 2 composition and gels with 0.99, 1.96, and 2.91 mol% La 2 O 3 added were sol–gel derived. The crystallization path, structure evolution, microstructure, and morphology of calcined premullite powders and sintered ceramic bodies have been investiga...
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| Published in: | Journal of the American Ceramic Society 2014-07, Vol.97 (7), p.2264-2271 |
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| Main Authors: | , , |
| Format: | Article |
| Language: | English |
| Citations: | Items that this one cites Items that cite this one |
| Online Access: | Get full text |
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| Summary: | Monophasic gel with stoichiometric 3
Al
2
O
3
·2
SiO
2
composition and gels with 0.99, 1.96, and 2.91 mol%
La
2
O
3
added were sol–gel derived. The crystallization path, structure evolution, microstructure, and morphology of calcined premullite powders and sintered ceramic bodies have been investigated as a function of
La
2
O
3
content and sintering temperature. In addition to mullite, spinel phase at about 980°C, and α‐alumina at above 1000°C were determined; however, neither
La
2
O
3
nor
La
‐related compounds had crystallized. The
La
2
O
3
predominately incorporated into the glassy phase, enhanced with
La
2
O
3
level, which affected both mullite structure and composition, as confirmed by electron microscopy, Rietveld structure refinement, determination of unit cell parameters, electron microscopy, and achieved density of the sintered bodies. Increased thermal treatment changes the alumina/silica ratio in mullite (towards 3:2 below 1200°C, and toward 2:1 above), and decreases the mullite/amorphous ratio. Sintered dense ceramic bodies revealed a positive densification effect and increased sinterability as a result of the lanthanum‐induced increase in glassy phase. |
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| ISSN: | 0002-7820 1551-2916 |
| DOI: | 10.1111/jace.12887 |