TiO2 as a sintering additive for KNbO3 ceramics

Improved densification during the conventional sintering of KNbO3 ceramics was achieved by using small additions of TiO2. This improved densification can be explained on the basis of high-temperature chemical reactions in the system. X-ray diffractometry and electron microscopy were used in combination with diffusion-couple experiments in order to elucidate the chemical reactions between KNbO3 and TiO2. TiO2 reacts with KNbO3 forming KNbTiO5, and a low concentration of Ti incorporates in the KNbO3 structure resulting in the formation of oxygen vacancies and, consequently, in an improvement in the densification. At ∼1037 °C eutectic melting between the KNbO3 and the KNbTiO5 further improves the densification of the KNbO3 ceramics.