Formation region of monophase with cubic spinel-type oxides in Mn-Co-Ni ternary system

This study was performed to find the composition area of cubic spinel-type monophase oxides composed of the Mn-Co-Ni ternary system. Starting material s were prepared by mixing Mn, Co, and Ni nitrates then evaporating to dryne ss. Each starting oxide was fired at 700, 800, 900, 1000, and 1100 degrees C in air. The regions of cubic spinel monophase (CSM) were confirmed to spr ead with decreasing firing temperatures. The region of CSM at 1000 degrees C was seen near the line connecting the points of Mn : Co : Ni = 2 : 4 : 0 and 4.5 : 0 : 1.5. The area at 800 degrees C spread toward Co and Ni, as co mpared to the results at 1000 degrees C. In the region containing more Mn a bove the area of CSM at 800 degrees C, the phase had tetragonal spinel or a lpha-Mn2O3 besides cubic spinel structure. Below this area, the phase conta ined rock-salt-type crystal besides cubic spinel structure. This tendency a t 1000 degrees C was the same as that at 800 degrees C. (C) 1999 Kluwer Aca demic Publishers.