Evaluation of softening deformation behavior in porcelain bodies during firing

Effects of green density, particle size of raw quartz, addition of corundum or Al(OH)₃, and applied bending stress on the softening deformation behavior during the firing process were studied for feldspathic porcelain bodies. The amount of the deformation displacement is highly influenced by the liquid-phase formation with rising bulk density in the range 1100-1200°C, and reduced by using raw quartz with a larger particle size or by adding alumina with a larger particle size. These particles make skeletons in the matrix and prevent liquid flow, resulting in low displacement. During the soaking time at the maximum firing temperature of 1200°C, the addition of Al(OH)₃ reduced the deformation rate; the quartz size had no effect on it. The Al(OH)₃ dissolves into the glass phase and increases its viscosity. The larger bending stress increased the deformation rate during soaking time.