Preparation of dispersed zirconia barium aluminosilicate composites

Synthesis of Ba_0.75Sr_0.25Al₂Si₂O₈ - ZrO₂ Ceramic Composites by Solid State Reaction of Mechanically Activated Precursor Mixtures

“…The proportions of conditioned FA (hereinafter denominated simply as "FA"), Al 2 O 3 , BaCO 3 , SrCO 3 and ZrO 2 required for the preparation of the stoichiometric mixtures Regarding the BAS-ZrO 2 and SBAS-ZrO 2 composites in which BAS and SBAS are present as Celsian, which are of particular interest in this work, we found that while some studies have been reported on the former composites (6)(7)(8)(9)(10)(11), no information whatsoever has been published in relation with the latter materials. However, the results that have been reported for BAS-ZrO 2 composites could serve as a starting point for the study of SBAS-ZrO 2 compositions.…”

“…This was probably due to the generation of transient liquid during the sintering process, but in an amount insufficient to produce a high degree of consolidation in the materials, leading to the presence in them of a residual glassy phase (10). Obviously, this temperature was also too low to produce a good sintering degree in the samples.…”

“…For instance, Debsikdar and Sowemimo (7) obtained relative densities of 95 % and 99 % for their materials described in the previous section of this paper. Nordmann et al (10) observed a significant increase in the rate of densification above 1300 °C, obtaining a maximum density of 3.52 g/cm 3 for a binary BAS-ZrO 2 composition containing ∼40 wt. % ZrO 2 and sintered at 1500 °C/2 h. This was attributed to the generation of transient liquid which started at 1300 °C, and which facilitated the densification of the material.…”

“…For instance, Sandhage and Fraser (6) obtained ZrO 2 employed by us remained dissolved in the remnant transient liquid, and then it probably remained dissolved in a glassy phase likely originated from that liquid during cooling of the samples, which was probably not detected by XRD due to its small amount. Consequently, not enough Y 2 O 3 remained in solid solution in the re-precipitated ZrO 2 to ensure its full stabilization into the tetragonal form (10,34).…”

“…However, the results that have been reported for BAS-ZrO 2 composites could serve as a starting point for the study of SBAS-ZrO 2 compositions. It is known that BAS and ZrO 2 are chemically compatible, in such a way that they are able to coexist at equilibrium over a broad temperature range (6)(7)(8)(9)(10). It has been suggested (6) that for the BAS-ZrO 2 composites enhanced fracture toughness may result from the tetragonal (t-ZrO 2 ) to the monoclinic (m-ZrO 2 ) transformation of ZrO 2 , in a manner analogous to other ZrO 2 -toughened ceramics.…”