MgO-Cr₂O₃系セラミックスの焼結特性と (Mg_8-xCr_x)Cr₁₆O₃₂ (0≦x≦2.88) の生成

抄録

MgO and Cr₂O₃ powders were mixed in various ratios and pressed to form compacts. They were heated in the carbon powder bed. Starting compacts containing 53 to 63mol% Cr₂O₃ were densely sintered, particularly the sintered compact with 55mol% Cr₂O₃ was about 93% in relative density, and composed of (Mg_8-xCr_x)Cr₁₆O₃₂ (0≤x≤2.88). Pores with globular shape in the compacts suggested the sintering in the presence of a liquid. Under reductive atmosphere coexisting with carbon, a liquid of the Cr-Cr₂O₃-MgO system is considered to form due to reduction of the Cr₂O₃ in the compact. During cooling, the (Mg_8-xCr_x)Cr₁₆O₃₂ may precipitate from the liquid. When the compound was exposed to air during heating, this phase was unstable and changed to MgCr₂O₄ and Cr₂O₃ at about 300°C.