Lightweight Porcelain Stoneware by Engineered CeO2 Addition

The use of porcelain stoneware in innovative applications such as the covering of internal walls or the manufacturing of ventilated facades may be limited by its relatively high density. In this paper, we discuss the achievement of a reduction in density of about 30%, coupled to a limited water absorption (about 2%), by the addition of CeO2 to the raw materials. This additive provides some porosity due to the evolution of oxygen, in turn caused by the high temperature reduction to Ce2O3. This gas formation depends both on sintering temperature, holding time, and is obviously affected by the concentration of additive. Two different processing strategies were found to match the density and water absorption requirements for the application of stoneware tiles. One involved the the control of the CeO2 content together with processing at high temperature for a limited holding time; the other one corresponded to the fabrication of a graded material, comprising a highly porous core (produced using a high content of CeO2) sandwiched between two external compact surface layers. The usage of porcelain stoneware in the coverage of vertical surfaces is limited by the relatively high density. It is discussed a reduction of density of about 30%, coupled to a limited water absoption (about 2%), by the addition of CeO2 in the raw materials. The porosity is caused by the evolution of oxygen, by high temperature reduction to Ce2O3, that depends both on sintering temperature, holding time, and concentration of additive.