カオリンとSrCO_3及びBaCO_3の反応による緻密質セルシアンセラミックスの調製

概要

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Reaction and sintering characteristics of mixtures of kaolin (Al_2O_3・2SiO_2・2H_2O) with BaCO_3 or SrCO_3 were investigated using kaolin and finely ground carbonate powders. Although the decomposition temperature of barium carbonate and strontium carbonate are higher than 1050℃, both carbonate powders decomposed at much lower temperature of about 800℃ and then reacted with decomposed kaolin to form amorphous materials. Thus formed amorphous materials are extremely sinterable, and pressed specimens can be rapidly sintered at about 950℃ by viscous flow. Densification is inhibited by the immediate crystallization of hexacelsian crystals (SrO・Al_2O_3・2SiO_2・or BaO・Al_2O_3・2SiO_2) at about 1000℃. Further densification was not observed at temperatures above 1000℃, because of completion of the crystallization of amorphous phases. Amount of SrO or BaO for sufficient sintering were larger than n=1.2 and n=1.6, respectively, with n being the mol ratio of SrO/Al_2O_3 and BaO/Al_2O_3. The reason of the difference in the n values was attributed to the difference in viscosity between the amorphous phases. Dense polycrystals consisting of mainly monoclinic Sr-celsian were obtained at about 1200℃.
社団法人日本セラミックス協会の論文
1999-07-01