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Influence of processing route and SiO2 on sintering ability, CTE, and dielectric constant of β-Si4 Al2O2N6
I. Ganesh, N. Thiyagarajan, D.C. Jana, , S.M. Olhero, J.M.F. Ferreira
Published in
Volume: 23
Issue: 9
Pages: 2305 - 2311
Dense β-Si4Al2O2N6 and β-Si4Al2O2N6-0.5 SiO2 ceramics were obtained from α-Si3N4, α-Al2O3, AlN, and Y2O3 upon sintering green bodies consolidated by aqueous gel casting. For comparison purposes, a β-Si4 Al2O2N6 was also prepared by the conventional dry-powder processing route. In the case of gel-cast β-Si4Al2O2N6, the as-purchased AlN powder was treated with H3PO4 and Al(H2PO4)3 prior to use along with α-Si3N4, α-Al2O3, and Y2O3. The gel-cast β-Si4Al2O2N6 exhibited superior hardness (1423 ± 6 Hv), fracture toughness (3.95 ± 0.3 MPa·m1/2), and coefficient of thermal expansion (CTE) (3.798 × 10-6/°C between 30 and 1000 °C) in comparison to the ceramic consolidated by conventional dry pressing, which exhibited only 1317 ± 5 Hv, 3.30 ± 0.2 MPa·m1/2, and 3.532 × 10-6/°C between 30 and 700 °C. The in situ-generated ∼9 wt% SiO2 has considerably reduced the dielectric constant and CTE of β-Si4 Al2O2N6 from 7.30 to 6.32 and from 3.798 × 10-6/°C to 3.519 × 10-6 /°C, respectively. The loss tangent property of the investigated materials was little influenced by the variation of chemical composition and processing route. © 2008 Materials Research Society.
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JournalJournal of Materials Research