Abstract
Kaolinite mixed with 10 to 30wt% CuO was fired at 900°-1000°C and the phase transformation during firing was studied by powder diffraction analysis. The addition of CuO markedly promoted formation of mullite and cristobalite from kaolinite. The copper spinet was formed at 950°-1000°C and the quartz solid solution was formed at 950°C. The lattice constants were precisely determined for the quartz solid solution. Of the two lattice constants of the quartz solid solution (c0 and a0), the value of c0 agreed with that for α-quartz, while the value of a0 was larger than that for α-quartz and was between that for α-quartz and that for β-quartz. Thus, the quartz solid solution has a structure in which a-axis is expanded. The value of a0 for the quartz solid solution decreased and the amount of copper spinel formed increased with an increase in CuO content. This results suggested that the amount of Cu2+ ion in the quartz solid solution did not change but the amount of Al3+ ion decreased with an increase in CuO content.
