Influence of Lampang pottery stone: local materials in Thailand on C-Q-F ratio, key properties, mullite formation and glaze-body fit of vitreous ceramic sanitary ware

Abstract

This study was aimed to investigate the key properties, mullite formation and glaze-body fit of sanitary ware bodies, by using pottery stone from Lampang, Thailand as a substitute for kaolin, feldspar, and silica. Seven samples of formulated bodies were prepared by wet milling, formed by plaster mold casting, and fired at 1175 °C, 1200 °C, and 1225 °C. Testings were carried out in accordance with ASTM C373-88, ASTM C326-09, ASTM C689-09, and ASTM C372-94. Phase analysis and microstructure of selected formulations were analyzed by using XRD and SEM. For the formulation having 37.7-20.7-41.6 of C-Q-F ratio and pottery stone in substitute for 100% silica, after firing at 1200 °C showed 9.27% total shrinkage, 0.17% water absorption, and 60 MPa flexure stress. The crystal structure resulted in higher amount of mullite. The linear thermal expansion and thermal expansion coefficient were lower to 0.34 and 7.07 × 10−6/°C, respectively. The difference of linear thermal expansion between the formulated body and commercial white-opaque glaze was − 0.02 at 500 °C. The shrinkage difference of body and glaze showed that the glaze-body fit was under slightly amount of compression. As a result, the formulation with the substitute for 100% silica could be vitrificated at lower temperature and indicated positive trends towards lower dunting during firing.