Peculiar properties of phase transitions in Na0.5Bi0.5TiO3-xBaTiO3 (0<x<6) lead-free relaxor ferroelectrics seen via acoustic emission

Na0.5Bi0.5TiO3-xBaTiO3 (0<x<6) relaxor ferroelectrics crystals were investigated by means of dielectric and acoustic emission methods. Dielectric curves exhibit the slightly visible small maxima near the depolarization temperatures, Td, and the wide maxima at the temperatures of Tm, whereas the acoustic emission exhibits the sharp bursts, corresponding to Td, Tlm, which is known to be a temperature exhibiting a strong frequency dispersion, TRE, which is known to be a temperature above which a frequency dispersion vanishes, and the Tm and the Tp manifesting a transition to the paraelectric phase. Based on the AE data it was established that all these characteristic temperatures shift down as x increases, but with different slopes. A mechanism of such the differences is discussed

Influence of uniaxial pressure on dielectric properties of (1-x)Na0.5Bi0.5TiO3–xSrTiO3 for x = 0.01, 0.04, and 0.1 ceramics

The publication costs of this article were covered by the Estonian Academy of Sciences and the University of Tartu.The conventional solid-state sintering was applied to synthesized (1-x)Na0.5Bi0.5TiO3-xSrTiO3 (x = 0.01, 0.04, and 0.1) ceramics. Dielectric measurements of these ceramics were taken in the temperature range from 20 to 600 °C, in the frequency range from 1 kHz to 2 MHz and under uniaxial pressure ranging from 10 to 1100 bar. The study of the dielectric behaviour showed that the influence of uniaxial pressure on the investigated properties was considerable. The peaks εm gradually decreased and shifted towards lower temperatures with an increase of uniaxial pressure for all samples. The first effect developed with an increase of the strontium ion concentration. Experimental results revealed most interesting properties of the material in the context of its potential applications.Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Temperature and E-Poling Evolution of Structural, Vibrational, Dielectric, and Ferroelectric Properties of Ba1−xSrxTiO3 Ceramics (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.45)

Poland’s high-performance computing infrastructure PLGrid (HPC Centers: ACK Cyfronet AGH) for providing computer facilities and support within computational grant no. PLG/2022/015969. Innovative research and scientific platform for a new class of nanocomposites, financed by the Ministry of Education and Science, contract number 7216/IA/SP/2021.Lead-free Ba1−xSrxTiO3 (BST) (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.45) ceramics were successfully prepared via the solid-state reaction route. A pure perovskite crystalline structure was identified for all compositions by X-ray diffraction analysis. The basic phase transition temperatures in these ceramics were studied over a wide temperature range. A change in symmetry from a tetragonal to cubic phase was detected, which was further proven by phonon anomalies in composition/temperature-dependent Raman spectra. The incorporation of Sr2+ into BaTiO3 (BT) lead to a shift in the phase transitions to lower temperatures, suppressing the ferroelectric properties and inducing relaxor-like behavior. Therefore, it was reasonable to suppose that the materials progressively lack long-range ordering. The initial second-harmonic generation (SHG) measurements demonstrated that the cubic phase of BST ceramics is not purely centrosymmetric over a wide temperature interval. We discussed the possible origin of the observed effects, and showed that electric field poling seems to reconstruct the structural ordering destroyed by the introduction of Sr2+ to BT. In the first approximation, substitution of Sr for larger Ba simply reduced the space for the off-central shift in Ti in the lattice and hence the domain polarization. A-site cation ordering in BST and its influence on the density of electronic states were also explored. The effect of doping with strontium ions in the BST compound on the density of electronic states was investigated using ab initio methods. As the calculations showed, doping BT with Sr2+ atoms led to an increase in the bandgap. The proposed calculations will also be used in the subsequent search for materials optimal for applications in photovoltaics. --//-- This is an open access article Suchanicz, J.; Sitko, D.; Stanuch, K.; Świerczek, K.; Jagło, G.; Kruk, A.; Kluczewska-Chmielarz, K.; Konieczny, K.; Czaja, P.; Aleksandrowicz, J.; et al. Temperature and E-Poling Evolution of Structural, Vibrational, Dielectric, and Ferroelectric Properties of Ba1−xSrxTiO3 Ceramics (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.45). Materials 2023, 16, 6316. https://doi.org/10.3390/ma16186316 published under the CC BY 4.0 licence.the Ministry of Education and Science, contract number 7216/IA/SP/2021; The Institute of Solid State Physics, University of Latvia at the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2

Thermal, Raman and dielectric study of 0.5K 0.5 Bi 0.5 TiO 3 –0.5PbTiO 3 ceramics

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Peculiar Properties of Phase Transitions in Na0.5Bi0.5TiO3-xBaTiO3 (0

<div><p>Na0.5Bi0.5TiO3-xBaTiO3 (0</p></div

Peculiar Properties of Phase Transitions in Na0.5Bi0.5TiO3-xBaTiO3 (0

<div><p>Na0.5Bi0.5TiO3-xBaTiO3 (0</p></div

Properties of Na0.5Bi0.5TiO3 Ceramics Modified with Fe and Mn

Na0.5Bi0.5TiO3 (NBT) and Fe- and Mn-modified NBT (0.5 and 1 mol%) ceramics were synthesized by the solid-state reaction method. The crystal structure, dielectric and thermal properties of these ceramics were measured in both unpoled and poled states. Neither the addition of iron/manganese to NBT nor poling changed the average crystal structure of the material; however, changes were observed in the short-range scale. The changes in shapes of the Bragg peaks and in their 2&Theta;-position and changes in the Raman spectra indicated a temperature-driven structural evolution similar to that in pure NBT. It was found that both substitutions led to a decrease in the depolarization temperature Td and an increase in the piezoelectric coefficient d33. In addition, applying an electric field reactivated and extended the ferroelectric state to higher temperatures (Td increased). These effects could be the result of: crystal structure disturbance; changes in the density of defects; the appearance of (FeTi&#712;-), (Mn&prime;Ti-V&bull;&bull;O) and (Mn&Prime;Tii-V&bull;&bull;O )&mdash;microdipoles; improved domain reorientation conditions and instability of the local polarization state due to the introduction of Fe and Mn into the NBT; reinforced polarization/domain ordering; and partial transformation of the rhombohedral regions into tetragonal ones by the electric field, which supports a long-range ferroelectric state. The possible occupancy of A- and/or B-sites by Fe and Mn ions is discussed based on ionic radius/valence/electronegativity principles. The doping of Fe/Mn and E-poling offers an effective way to modify the properties of NBT