Naslov
The effect of La2O3 addition on sol–gel derived mullitization

Autori
Mandić, Vilko ; Tkalčec, Emilija ; Kurajica, Stanislav

Izvornik
Journal of the American Ceramic Society (0002-7820) 97 (2014), 7; 2264-2271

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
mullite ; sol-gel ; crystallization ; Rietveld

Sažetak
Monophasic gel with stoichiometric 3Al2O3*2SiO2 composition and gels with 0.99, 1.96, and 2.91 mol% La2O3 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 La2O3 content and sintering temperature. In addition to mullite, spinel phase at about 980°C, and a-alumina at above 1000°C were determined ; however, neither La2O3 nor La related compounds had crystallized. The La2O3 predominately incorporated into the glassy phase, enhanced with La2O3 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.

Izvorni jezik
Engleski

Znanstvena područja
Kemijsko inženjerstvo

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