1986 Volume 94 Issue 1088 Pages 440-448
CO3(PO4)2⋅8H2O was treated hydrothermally under the saturated vapor pressure at temperatures between 150° and 350°C. Co3(PO4)2⋅8H2O was placed in a micro-autoclave with water and was heated under several conditions. Characteristics of the obtained crystals, such as morphology, color and thermal stability were investigated. In particular, the colors were discussed on the basis of the spectral reflectance. Co3(PO4)2⋅8H2O changed to 2Co3(PO4)2⋅7H2O (platy: 2×20μm, light bluish purple) under hydrothermal condition at 150°C for 120h, to Co3(PO4)2⋅2H2O (granular: 28-46μm, dark purplish red) at 200°C for 48h, to Co3(PO4)2⋅H2O (needle-like: 17μm, light reddish purple) at 250°C for 72h, and to Co3(PO4)2 (platy: 7×10μm, deep reddish violet) at 350°C for 120h. 2Co3(PO4)2⋅7H2O, Co3(PO4)2⋅2H2O, Co3(PO4)2⋅H2O showed endothermic peaks due to dehydration at 393°C, 470°C, and 566°C on DTA curve, respectively. Addition of ZnCl2 to the hydrothermal solution remarkably accelerated the crystal growth of the obtained crystals, and their morphologies were considerably different from those without additives
