External-field-induced crystal structure and domain texture in (1−x)Na0.5Bi0.5TiO3–xK0.5Bi0.5TiO3 piezoceramics

The dielectric relaxation and electrical conduction were investigated in (BixNa1−x)0.94Ba0.06TiO3 (Abb. xBNBT6, x = 0.5, 0.495, 0.485, and 0.475) ceramics prepared by solid state reaction. With a decrease in x, the dielectric properties of the ceramics decreased, whereas the electrical conduction increased, resulting in a transition from insulator to oxide‐ions conductor. When x = 0.475, the ceramics exhibited large conductivity (~10−3 S cm−1 at 575°C) and low activation energy (~0.45 eV), indicating their potential application in solid oxide fuel cells. A mixed conduction mechanism with oxide‐ions, electrons, and holes was proposed. With a decrease in x from 0.495 to 0.475, it was found that the p‐type conduction was switched to n‐type conduction. The dielectric relaxation of the x = 0.495 sample was associated with short‐range hopping of oxygen vacancies. However, the dielectric properties of the x = 0.485 and 0.475 samples can be explained by Maxwell‐Wagner interface relaxation.

P m \bar{3} m

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dielectric relaxation and electrical conduction in (Bi_xNa_1−x)_0.94Ba_0.06TiO₃ ceramics

Jing

et al. 2017

“…If doped with a barium content of around 6% or potassium content of around 20%, BNT‐based solid solutions appear cubic to XRD . Contrastingly, superlattice reflections in neutron diffraction and transmission electron microscopy (TEM) and selected area electron diffraction (SAED) suggest the presence of a lower symmetry, providing the coexistence and interconversion fact for R 3 c and P 4 bm symmetries at a wide temperature range …”

Section: Resultsmentioning

confidence: 99%

Domain‐scale imaging to dispel the clouds over the thermal depolarization of Bi_0.5Na_0.5TiO₃‐based relaxor ferroelectrics

Yin

Liu

2019

Thermal depolarization temperature, Td, of ferroelectric oxides Bi0.5Na0.5TiO3 (BNT), where dielectric and piezoelectric signals exhibit remarkable changes, is providing rich research contents but is not well understood yet. Herein, on the domain‐scale, we give the direct and clear real‐space images of thermal depolarization process on BNT‐based complex oxides. As disclosed by the piezoresponse force microscopy (PFM), heating above Td breaks the poling‐induced large‐sized‐oriented domains into smaller sized polar clusters with different orientations, leading to the thermal depolarization phenomenon. Although the poling‐induced domain decays above Td, the broken domains exhibit a rather larger coherence length than that of the incipient labyrinth‐like nano‐domains. During the heating process, BNT possesses a structural transition from the long‐range‐correlated R3c (a−a−a− anti‐phase tilting) to the short‐range‐correlated P4bm (a0a0c+ in‐phase tilting) phase, which should be the fundamental driving force for the fluctuations of poling‐induced large‐sized‐oriented domains. We expect these results will further promote the understanding about the origin of Td in BNT‐based relaxor ferroelectrics, and provide an intuitive method for the characterization of the thermodynamic and kinetic process in this kind of materials.

“…It is generally believed that the optimal properties of ferroelectric ceramics can be achieved under condition of multiphase coexistence, such as morphotropic phase boundary (MPB) . In ferroelectric materials with compositions near MPB, the free energy difference between phases is small, which means that phase transition can be easily induced by external conditions such as stress and electric field . In particular, electric field–induced phase transition is widely concerned because it can tune or improve the properties of ferroelectric materials, simply by adjusting the voltage.…”

Section: Introductionmentioning

confidence: 99%

Quantitative analyses of electric field–induced phase transition in (Na, K)_0.5Bi_0.5TiO₃:Eu ceramics by photoluminescence

Zeng

Zhou

2019

Most reported results about phase transition probed by the photoluminescence (PL) spectra of Eu 3+ ions are qualitative, but the quantitative analyses of phase transition were presented in this work. We fabricated (Na 0.8 , K 0.2 ) 0.5 Bi 0.497 Eu 0.003 TiO 3 (NKBT20:Eu) ferroelectric ceramics and investigated the phase structures and the PL spectra of NKBT20:Eu ceramics before and after poling at different electric fields.The PL spectra indicate a phase transition from tetragonal phase (T phase) to rhombohedral phase (R phase) within NKBT20:Eu ceramics after poling, consistent with the analyses by X-ray diffraction (XRD). Moreover, the emission intensity ratios of the "hypersensitive" transition 5 D 0 → 7 F 2 to the magnetic dipole transition 5 D 0 → 7 F 1 could be used to calculate the fractions of the phase transition quantitatively, which were further confirmed by XRD Rietveld refinements. This study provides a different perspective to investigate the phase transition induced by electric field for NKBT20:Eu ceramics, qualitatively and quantitatively, and the method is expected to be useful in more cases of phase analyses.