Low-firing of CuO-doped anatase

The effect of CuO additions on the firing temperature of the anatase phase of TiO2 has been investigated using X-ray diffraction, transmission electron microscopy, and dilatometry. It was found that the addition of 2 wt% CuO to TiO2 anatase significantly lowered the sintering temperature to similar to 900 degrees C. The presence of a CuO-rich intergranular phase in the sample was observed and was attributed to the presence of a liquid phase during sintering. The addition of CuO to anatase phase TiO2 lowered the phase transformation temperature as well as the temperature of a shrinkage anomaly. This shrinkage anomaly is apparent in a temperature region showing a reversal of the shrinkage rate. The low-firing of CuO-doped anatase was attributed to the association of two distinct mechanisms: the formation of CuO-rich liquid phase at higher temperatures and a shrinkage onset present at lower temperatures associated with the phase transformation. (C) 1999 Elsevier Science Ltd.