C.M. López-Badillo
The main objective of this research work was to study the influence of glassy additives on
the formation of crystalline phases in sintered red ceramic bodies used for the fabrication of
ceramic floor tiles, whose composition is a mixture of quartz (SiO2), kaolinite [Al2Si2O5(OH)4],
albite (NaAlSi3O8), muscovite [KAl2(Si3Al)O10(OH)2] and calcite (CaCO3). The additives used
were: fly ash, soda-lime glass, borosilicate glass, glass frit, Na2P3O10 and cryolite (Na3AlF6).
These were added in variable proportions to the nominal composition of the red ceramic bodies,
either as single or as combined additions, aiming to accelerate the densification of the materials
during their sintering process. For all the additive types used, the crystalline phases formed in the
samples sintered using a peak temperature ranging from 950 to 1030 ºC were: quartz (SiO2),
anorthite (CaAl2Si2O8), and hematite (Fe2O3). It is known that the presence of anorthite is
particularly beneficial for the mechanical properties, chemical stability and densification of the
sintered red ceramic bodies. However, some of the considered additions tended to be detrimental
for the formation of this phase in the studied materials, especially at the lowest peak sintering
temperature employed. This was verified by means of XRD and SEM analysis.
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