Effect of Grain Size of Petalite on the Properties of Petalite Ceramics

Abstract

In the previous paper the authors have reported that addition of a small amount of pulverized lithia-containing glass to the powdered natural petalite increased the firing range of their pressed mixture, improving modulus of rupture and thermal shock resistance of their sintered body (J. Ceram. Assoc. Japan, 70, 8 (1962)).In the present study the effects of fineness of the Petalite powder on the above behaviors were investigated. 12 kinds of batches comprising 10% by weight of the pulverized glass (finer than 325 mesh; 10.7 Li2O, 8.9 MgO, 8.9 Al2O3, 71.5% SiO2 by weight) and 90% of each one or two of the powdered petalites of different fineness (40-80, 80-200, 200-325, >325 mesh) (see Table 2) were prepared, pressed into the bars of 5×5×50mm, and fired at 1250-1280°C until their porosity reached almost zero. The batches consisting of no glass frit were also prepared for the comparison.The results obtained are summarized as follows: (1) With decreasing the grain size of petalite powders, the firing range and the firing shrinkage of the pressed body increased. (2) With decreasing the grain size of petalite powders, the modulus of rupture and the heat shock resistance of the sintered body were improved. (3) For the body comprising petalite powder finer than 200 mesh, water-quenching from 1000°C increased the modulus of rupture of the sintered body. For the body comprising the petalite grains coarser than 80 mesh, however, the reversed effect was observed. (4) With decreasing the grain size of petalite powders, the thermal expansion coefficient of the sintered body decreased, reaching almost zero.From above results, it was concluded that the garin size of petalite powder for making petalite-ceramics should be below 200 mesh.