Mg^<2+>-置換型遷移アルミナ粉末を用いたパルス通電焼結によるサブミクロンアルミナセラミックスの作製

概要

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Dense submicron-grained alumina ceramics were fabricated by pulse electric current sintering (PECS) using Mg^<2+>-doped transition alumina powders at 1200-1350℃ under a uniaxial pressure of 40 or 80 MPa. The Mg^<2+>-doped transition alumina powders (0-0.50 mass% MgO base) were prepared through a new sol-gel route using high-purity polyhydroxoaluminum (PHA) and MgCl_2 solutions as starting materials. The composite gels obtained were calcined at 900℃ and ground by planetary ball-milling. Upon heating, the composite gels transformed into a single-phase γ-alumina or mixed phase of γ-and χ-aluminas, depending on the MgO content. The resultant transition alumina powders were solid solutions, in which Mg^<2+> cations were substituted into the crystal lattice. The powders were re-calcined to increase the content of α-alumina particles, which act as seeding for low-temperature densification. Densification depended on the MgO content and loading pressure. The critical Mg^<2+>-doping for suppressing grain growth was found to be 0.10 mass% MgO. Higher loading pressures led to full densification at lower temperatures, resulting in a more uniform and finer microstructure. Thus, dense alumina ceramics (relative density≧99.6%) with a uniform microstructure composed of fine grains with an average size of 0.47μm could be obtained by PECS at 1250℃ under 80MPa.
社団法人日本セラミックス協会の論文
2006-02-01