Solid State Reactions of Calciumphosphates with Aluminosilicates
1977 Volume 85 Issue 984 Pages 397-403
Details
1977 Volume 85 Issue 984 Pages 397-403
In order to collect fundamental data on mechanism of vitrification occurring in bone china bodies during firing, solid state reactions of calciumphosphates with aluminosilicates were investigated. Pt-marker method and EPMA method were used for examining the species and diffusing direction of diffusive elements, and X-ray diffraction method was also used for determination of crystalline phases formed in the reaction.
Ca2P2O7 which was a decomposition product of CaHPO4⋅2H2O released a part of its P2O5-component and made it diffuse into the aluminosilicate layer, while the remainder was transformed into Ca3(PO4)2. Hydroxyapatite released a part of its CaO-component and made it diffuse into aluminosilicates, while the remainder was also transformed into Ca3(PO4)2. The Ca3(PO4)2 was not reacted with aluminosilicates in solid state reaction and persisted stably in it. The diffusion might be affected appreciably by crystal structure of host-minerals, and the clay minerals were more reactive than the other aluminosilicates. In the solid state reactions, P2O5-component and CaO-component preferentially diffused into the clay minerals and the former facilitated melting and the latter reacted with the clay minerals and formed anorthite. Kaolinite was much more reactive than the other clay minerals. In the case of forming anorthite, pyrophyllite and sericite were more reactive with CaO-component than kaolinite.
