ゾル-ゲル法によるMgO添加ムライト/ZrO_2複合微粉末の合成と焼結

概要

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Mullite/15 vol% ZrO_2 composite powders doped with MgO were synthesized using sol-gel method. The effects of MgO addition on the powder characteristics, sinterability, microstructure and mechanical properties have been investigated. The addition of more than 0.3 wt% MgO resulted in the formation of ZrSiO_4 when calcined at 1400℃. This reaction is ascribed to the liberation of SiO_2 from mullite grains due to the exsolution of MgO. ZrSiO_4 decomposed to t-ZrO_2 and SiO_2 liquid phases during sintering process. The decomposition temperature decreased as the MgO content increased, and the lowest decomposition temperature of 1440℃ was observed in the composition containing 1.0 wt% MgO. The sinterability of composite powders was greatly improved by the addition of MgO. The densification temperature necessary to achieve a relative density of higher than 99% was lowered from 1630° to 1450℃ by the 1.5 wt% MgO addition. Although the remarkable grain growth was observed with an increased addition of MgO, the amount of t-ZrO_2 in the specimens were also increased. Due to the transformation toughening, the mechanical properties were improved, such as flexural strength of 560 MPa and K_<IC> value of 5.8 MPa ・m^<1/2> for the 1.5 wt% MgO doped composite fired at 1475℃.
社団法人日本セラミックス協会の論文
1992-02-01