Abstract

Stoichiometric potassium niobate (KNbO₃) and materials with K- and Nb excess show marked differences in sintering behaviour and microstructure. Shrinkage is shifted to lower temperatures in material with K-excess and to higher temperatures in material with Nb-excess compared to the stoichiometric KNbO₃. The stoichiometric material densified to 4.36 g/cm(3), whereas the densities of the off-stoichiometric materials remained lower. Abnormal grain growth leading to grains up to 500 pm in size was observed for stoichiometric KNbO₃. K-excess KNbO₃ shows cuboid grain shape with size between 20 and 60 Rm. In the Nb-excess KNbO₃ the grains remain small. Approaches to improve the densification of the KNbO₃ materials are discussed by investigating processing variations specific for each composition. The objective of our work is to analyze the interrelations between stoichiometry, materials characteristics and processing stability of alkaline niobate ceramics. The results on KNbO₃ mark a starting point for investigations on complex high performance systems.