Dolomite, wollastonite and calcite as different CaO sources in anorthite-based porcelain

Anorthite-based porcelain was fabricated by using ball clay, quartz, alumina, feldspar and three different sources of CaO as raw materials. The effect of CaO sources such as dolomite, wollastonite and calcite on the mechanical, thermal and aesthetical properties of anorthite-based porcelain was investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies were also carried out to analyze the microstructure. Anorthite was formed as major phase in all the samples fired at their optimum sintering temperatures (1200, 1215 and 1230 °C). The sample with dolomite had the highest bulk density but the smallest flexural strength due to formation of substantial glassy phase. The maximum flexural strength (∼110 MPa) was reached in the sample containing wollastonite, which was mainly attributed to the favorable microstructure. Anorthite as the single crystalline phase was found in the sample with calcite and the sample showed the lowest thermal expansion coefficient and the highest whiteness, which was similar to bone china in appearance.