In her master's thesis, Martina Štefko studied the topochemical conversion in molten salt from Bi4Ti3O12 to A-site substituted complex perovskite Ba1-xSrxTiO3. She found that the Ba / Sr ratio in the resulting perovskite plates was smaller than that in the initial reaction mixture, what confirmed that Sr incorporated more than Ba. Since the relation between the Sr content (x) in the final Ba1-xSrxTiO3 plates and those in the reaction mixture (x') is almost linear (x=2.7 x'), an arbitrary Ba1-xSrxTiO3 composition (0≤ x≤1) could be prepared by this method. PFM research showed that perovskite plates with (0≤x≤0.175) exhibited ferroelectric and piezoelectric characteristics. Ba1-xSrxTiO3 plates with 0≤x≤0.11 showed (001) a preferencial orientation and a clear (001) / (100) tetragonal splitting that indicated the presence of c- and a-ferroelectric domains. It was found that with increase of Sr content a domains increased on the account of diminishing of c-domains.
D.10 Educational activities
COBISS.SI-ID: 1537612995In this invited lecture, we presented our findings concerning tailoring the shape, the crystal structure and preferential orientation of BaTiO3 plates. We also presented potential applications in which we can take advantage of the defined shape and preferential orientation of BaTiO3 plates and their ferroelectric and piezoelectric properties.
B.04 Guest lecture
COBISS.SI-ID: 29847079Based on the classic theories of growth of grains and crystallites (Ostwald ripening and Lifshitz-Slyozov-Wagner (LSW)), we assumed that the preparation of ceramics from particles with well-developed faces required different approaches than those from spherical particles, for which normal grain growth is expected. In our study we selected BaTiO3 nanoparticles with an intermediate shape which was not completely spherical, but the surfaces were not completely smooth. In the sintering of such particles, different types of grain growth are expected from normal, exaggerated and stagnant. We studied how we can control the grain growth by means of different sintering modes (isothermal or two-stage) and how the presence of different grains affects the ferroelectric and dielectric properties of ceramics.
B.04 Guest lecture
COBISS.SI-ID: 31265319In this invited lecture, we presented the mechanism for topochemical conversion from Bi4Ti3O12 to MTiO3 (M = Ba, Sr, Ca) plates under hydrothermal conditions. This transformation has not yet been described in the literature. The mechanism of this conversion was systematically studied for SrTiO3. We found out that this transformation is topochemical (SrTiO3 preserves the form of Bi4Ti3O12) only in case of carefully controlled synthesis conditions, which enabled the epitaxial growth. In this topochemical transformation, (100) oriented SrTiO3 plates formed from (00l) Bi4Ti3O12 plates. We have shown that in a similar way it is possible to dictate the conversion into BaTiO3 and CaTiO3 plates.
B.04 Guest lecture
COBISS.SI-ID: 31269159Member of the Editorial board of the international scientific journals
C.06 Editorial board membership