Novel ceramics prepared from inferior clay rich in CaO and Fe2O3: Properties, crystalline phases evolution and densification process

Inferior clay rich in CaO and Fe2O3 is a typical clay with huge reserves in southwest of China, which cannot be used in traditional aluminosilicate system ceramics. To efficiently utilize the inferior clay, a method of preparing novel ceramics containing CaO and Fe2O3 was put forward. In this study, effects of inferior clay proportion on properties, CaO on evolution of crystalline phases and Fe2O3 on densification process were analyzed by XRF, XRD, TG-DTA and SEM-EDS combined with physical properties tests. The results showed that addition of inferior clay (from 20 to 70 wt%) significantly affected sintering temperature (from 1190 to 1130 °C). High activity CaO decomposed by carbonate transformed into anorthite and diopside at low temperature. Fe2O3 promoted generation of low-temperature liquid phase, which facilitated densification process. The fired ceramics (60 wt% inferior clay) sintered at 1130 °C exhibited excellent properties with water absorption of 0.05%, linear shrinkage of 6.8% and flexural strength of 70 MPa. This batch was applied into an industrial experiment and 1160 m2 qualified ceramics (ISO 10545-4:2004) were fabricated.