Effects of firing atmosphere on low temperature sintering of Al2O3 with a small quantity of CuO-TiO2-Nb2O5-Ag2O additives

The present study focused on firing atmosphere to obtain new findings on low temperature sintering mechanism of Alumina (Al2O3) with a small quantity of CuO-TiO2-Nb2O5-Ag2O additives. In particular, effects of three kinds of firing atmosphere, N2, air and O2, on sintering behavior of alumina with the CuO-TiO2-Nb2O5-Ag2O additives were investigated. At the firing temperature of 800 °C, start of densification was observed in all samples. The sintering density was in the order of N2 ≒ air > O2. At the temperature range between 800 and 900 °C, degrees of increase in sintering density in air and O2 atmosphere were larger than that in N2 atmosphere. The sintering density became to be in the order of air > O2 > N2. At 900 °C, the sintering density of only the sample fired in air atmosphere almost reached 3.79 g/cm3, which was 95 % of the theoretical density of alumina, 3.99 g/cm3. Analyses of additives by DTA and an XRD indicated that melting temperature and produced compounds varied with the change of firing atmosphere. It was presumed that these two factors mainly affected the sintering performance.