Abstract
The formation of microcracks in ceramic body made from industrially important ceramic clay Arumetsa was followed by the acoustic emission (AE) technique during firing. The maximal firing temperature varied between 900 degrees C and 1100 degrees C.
AE signals were more intense during cooling stage of firing. The first AE signals, reflecting the formation of microcracks, appeared at similar to 800 degrees C during the cooling stage of firing.
Only weak AE signals were detected in the heating stage of firing. Around the temperature of the beta ->alpha phase transition in quartz (573 degrees C) a minimum of AE signals was observed.
AE signals were attributed to the formation of microcracks which resulted from different coefficients of thermal expansion of contained mineral phases. The activity of AE signals increased with increasing maximal firing temperature.
The observed AE signals were correlated with decreasing Young's modulus during cooling below 573 degrees C. Cyclic heating-cooling experiment of fired ceramic body revealed recovering grain-glass contacts at temperatures above 800 degrees C.