The paper, which was published in a high-impact journal (Advanced Functional Materials, IF 11.805, source JCR), explains the complex relationship between the nanoscale electrical conductivity at domain walls in BiFeO3 and its macroscopic piezoelectric response. An interesting combination of electromechanical measurements both at the nanoscale and macroscopic (millimetre) scale revealed that the conductivity localized at the ferroelectric and ferroelastic domain walls has a marking effect on the mobility of these walls and thus on the macroscopic piezoelectric behaviour. This new mechanism, referred to as the “nonlinear piezoelectric Maxwell-Wagner effect”, may be in principle present in ferroelectrics containing boundaries or interfaces that can both displace under external fields and exhibit enhanced electrical conductivity (such as domain walls in BiFeO3).
COBISS.SI-ID: 28359975
The effect of the processing conditions on the B-site ordering in the relaxor perovskite Pb(Sc0.5Nb0.5)O3 ceramics, and consequently also on its functional properties, was demonstrated. In contradiction to previous observations on the ceramics, prepared from the solid-state synthesized powders, which show a distinctive B-site cation ordering when annealed below 1200 °C, in the mechanochemically derived ceramics no such ordering could be detected, regardless of the conditions of thermal post-annealing.
COBISS.SI-ID: 28843815
Equilibrium vapour pressures of sodium and potassium over KxNa1-xNbO3 solid solution within its whole compositional range at temperatures between 1173 K and 1303 K were determined by Knudsen Effusion Mass Spectrometry. The equilibrium vapour pressure of potassium over K0.5Na0.5NbO3 (KNN) is a few times larger than that of sodium, i.e., 8·10-3 Pa as compared to 3·10-3 Pa at 1263 K. The comparison of the obtained results to the well-established lead-based piezoelectric systems revealed, that the vapour pressure of alkalis over the respective niobates at 1200 K is almost three orders of magnitude lower as compared to the values reported for lead oxide over Pb(Zr,Ti)O3.
COBISS.SI-ID: 28837927
The electrocaloric effect (ECE), i.e., the conversion of the electric into the thermal energy has recently become of great importance for development of a new generation of cooling technologies. Here, we explore utilization of [Pb(Mg1/3Nb2/3)O3]0.9[PbTiO3]0.1 (PMN-10PT) relaxor ceramics as active elements of the heat regenerator in an ECE cooling device. We show that the PMN-10PT relaxor ceramic exhibits a relatively large electrocaloric change of temperature TEC )1 K at room temperature. The experimental testing of the cooling device demonstrates the efficient regeneration and establishment of the temperature span between the hot and the cold sides of the regenerator, exceeding several times the TEC within a single PMN-10PT ceramic plate.
COBISS.SI-ID: 13878299
We studied the microstructure and dielectric properties of Ba0.5Sr0.5TiO3 thin films on polycrystalline alumina substrates with film thicknesses in the range 90–400 nm. Upon annealing at 900 °C the films crystallized in a pure perovskite phase with uniform and dense microstructures consisting predominantly of columnar grains. The dielectric permittivity in kHz and GHz ranges and tunability exhibited a nonlinear dependence on the film thickness, reaching the peak values at about 240 nm, which was explained by the dielectric grain-size effect for the thinner films and release of biaxial stress by formation of nanocracks for the thicker films.
COBISS.SI-ID: 28751655