Investigation of surface and colloid chemistry of alkaline niobate piezoceramic powders

In this study, stability of members of lead-free and enviromental friendly alkaline niobate piezoceramic powders, potasyum niobate (KNbO3- KN), sodium niobate (NaNbO3), and their solid solution in morphotropic phase boundary (MPB) where x=0,5 potassium sodium niobate (KxNa1-xNbO3 ? KNN) in aqueous solutions were investigated in case of aging time, medium pH, compositional difference, and particle size parameters. In both three systems, pH drifts as a function of time has proved that the active system consumed and/or produced H+ and OH- ions. General profile in ICP results in fixed pH and time parameters showed that in A site cations, the low ionic potantial potassium cations dissoluted more then sodium ions. Whereas, the B site cation, higher ionic potantial among them, niobium dissoluted less. By the experienced results, dissolution mechanisms for KNN system has been discussed. It is observed that the system goes diffusion controlled incongruent dissolution by interpretting the linear regression method with applying kinetic models and normalized data in terms of surface area of the particle. In addition, reactive surface layer on the particle was calculated based on experimental data and this value was compared with the transmission electron microscope (TEM) image of aged sample. Studies showed that the reactive surface layer thickness values by the experimented data and the observed image data were in reasonable tolerance.