Alkaline niobate-based ceramics are presently among the most promising environment firendly candidates to replace lead based one. The mechanism of solid state synthesis of KNN has not been studied previously. We performed a diffusion-couples study of the model systems: Na2CO3/Nb2O5, K2CO3/Nb2O5 and (Na2CO3 +K2CO3)/Nb2O5. We identified the phases formed by interface reactions, determined diffusion coefficients and established that potassium ions were the rate limiting species. (1) A detailed microstructural analysis of KNN ceramics contributed to a better understanding of the synthesis. (2)
COBISS.SI-ID: 21602343
Research of methods of growth of piezoelectic single crystals has been stimulated by the their high functional properties. By expoiting a new method of single crystal growth, based on the exaggerated grain growth in ceramic matrices (Solid State Crystal Growth - SSCG) we were the first to prepare single crystals of lead-free piezoelectrics KNN and LiTaO3-modified KNN. Results of the research have been presented in three papers. We cite only the last one, which also contains references of our earlier works.
COBISS.SI-ID: 21571111
Based on the structural conditions for relaxor behavior of ceramic materials we proposed that by exchange of both A- and B-site ions with cations with compensating oxidation states in perovskite ferroelectric K0.5Na0.5NbO3 (KNN) we could achieve local charge fluctuations and consequently relaxor behavior. The model worked. The exchange of alkali ions with strontium, and niobium with titanium ions, in the range between 10 and 33 at. % resulted in materials with pure relaxor behavior. The ceramics is prepared in transparent form. KNN-SrTiO3 ceramics are the first transparent lead-free relaxors.
COBISS.SI-ID: 18252071
We were the first to show that chemical homogeneity, of PZT films stemming from different reactivites of individual reagents, influences the functional propeties of the films. We traced chemical homogeneity, specifically the local environment of Zr-atoms in the sols and amorphous films by EXAFS spectroscopy. By selective chemical modification of Zr-alkoxide we decreased its reactivity, consequently we reduced its segregation in the PZT sol. We prepared PZT films with excellent ferroelectric properties at lower temperatues of crystallization in comparison to unmodified PZT films.
COBISS.SI-ID: 1946212
High-energy milling or mechanochemical synthesis of ceramic powders is one of the promising synthetic routes of nanometre-sized ceramic powders. There is only a limited number of studies available on the mechanism of reactions, which are triggered by high-energy impacts in the mill. A cumulative kinetic energy, independent of the energy and frequency of impacts, is needed for the synthesis of NaNbO3. We were the first to show that the mathematical model and the milling maps, originally developed for metallic systems, could be applied to oxides.
COBISS.SI-ID: 20282919