Abstract
Bending creep rates for fired specimens (3×1×0.2cm) of Amakusa Touseki (pottery stone, chiefly containing quartz, sericite, kaolinite and 0.97% Fe2O3) and alumina-added (-30%) products were measured. A bending creep curve up to 3h consisted of primary and secondary steps. The creep rate (10-7-10-4s-1) in the primary step slowly decreased with increasing bending strains and then decreased rapidly in the secondary step. The mean creep rates in the primary step were obtained in the temperature range from 900 to 1050°C under stresses of 5, 10 and 20MPa. These primary creep rates decreased with alumina addition. The creep rate vs. creep stress showed linear relations on the log-log diagram, and their mean slope values were 1.26±0.27, suggesting a presence of a rate-determining step of diffusion or solution-precipitation reaction in the viscous liquid of the grain boundary. The amount of the viscous liquid phase was estimated as 38 to 21% for the alumina additions of 0 to 30% at 985°C (temperature of the liquid phase formation) in the system K2O-Al2O3-SiO2 and its composition of the liquid was estimated 10% K2O, 11% Al2O3 and 79% SiO2. However, the added alumina almost remained without reaction. The decreasing activation energies from 450kJ⋅mol-1 to 150kJ⋅mol-1 with alumina additions up to 30% were obtained.
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