The bismuth layer ferroelectric group has been extensively investigated for their use as high-temperature piezoelectric and as non-volatile ferroelectric memories, due to their high ...ferro-paraelectric phase transition temperature and their excellent fatigue strength. Ceramics made from strontium bismuth niobate (SrBi
2
Nb
2
O
9
) are promising alternatives to lead-based ceramics. The electrical properties of SrBi
2–
y
Y
y
Nb
2–
x
V
x
O
9
(0 ≤
x
≤ 0.2 and 0 ≤
y
≤ 0.2) ceramics as a function of temperature and frequency have been investigated. The mechanism by which the overlapping large polaron tunneling model (OLPT) is the adequate model for this compound at wide-ranging temperatures. Measurement data are discussed using the variable range hopping (VRH) theory. Eventually, the behavior of the ceramic compound is fitted by VRH. The activation energy, obtained from the graph of
σ
DC
versus temperature, is quite close to the VRH hopping energy. This suggests that the oxygen vacancies may act as polarons. The relaxation mechanism is mainly dominated by the short-distance mobility of the charge carriers caused by the non-Debye process.
Citric acid solution and solid state are paired to prepare Sm-doped Sr
1 − x
Ba
x
Bi
2
Ta
2
O
9
(x = 0, 0.05) ceramics in a way that byproducts are not released. XRD technique demonstrated that the ...compounds maintained orthorhombic structure, whereas lattice parameters analysis showed that dopants induce distortion of the orthorhombic unit cell. SEM revealed that plate-shaped dense ceramics can be fabricated. The electrical study sheds light on the influence of motif on carrier transport in Sr
1 − x
Ba
x
Bi
2
Ta
2
O
9
(x = 0, 0.05) ceramics. A partial Sm/Ba occupational disorder in lattice structure induces a diffuse phase transition. Compared to pure samples, the effect of samarium on dielectric properties was markedly revealed, reducing dielectric loss and enhancing the dielectric constant at room temperature. The electoral study carried out at higher temperatures, suggests that the mobility of the charge carrier is mainly due to a hopping mechanism according to the correlated barrier hopping (CBH) model fitted to hopping conduction. Through the electrical modulus model, the mobility of the charge carriers in the system is involved in a long-short-range hopping approach. Sm-dopant content leads to an upshift in the barrier energy of the AC, DC, and CBH conductivity models. Thus, when Sm atoms go up to 1.37 at% (x = 0.1) may hamper the free movement of charge carriers, leading to lower tanδ values.
A binary NaNO
3
-KNO
3
(45–54% weight ratio) solar salt was used to prepare Gd-doped SrBi
2
Ta
2
O
9
compounds. It is found, through the X-ray diffraction technique, that the solubility of Gd
3+
ions ...in the Bi
3+
site leads to cell volume shrinkage. Among the experienced difficulties figuring out mainly the undesired reaction that could occur between raw materials and molten-salt mixture involving a secondary phase. Fourier transform infrared and Raman techniques revealed that the incorporation of gadolinium into SrBi
2
Ta
2
O
9
lattice brings small shifts in vibrational frequency. The string process used in this work has led to non-negligible mass loss, which effectively affects the experimental density of ceramics. Along with scanning electron microscopy, the ceramics not only are composed of plat-like grains but also, they are reduced in thickness by doping. Compared with the pure SrBi
2
Ta
2
O
9
, dielectric constant and dielectric loss of doped samples with different gadolinium concentrations are significantly enhanced. However, both constants, since carrier generation is the same under a different bias voltage. Meanwhile, the long-distance motion of the charge carriers’ conduction mechanism depends, mainly, on microstructure and gadolinium concentration rather than bias voltage. The undoped sample is almost n-type conductivity that is predominant in oxygen-deficient. The more gadolinium is introduced into the structure the more the radius of Nyquist impedance is expanded, leading to the reduction of oxygen vacancies.
Tb-doped
BaTiO
3
nanoparticles are prepared using the sol–gel method. The characterization was carried out using X-ray diffraction powder (XRD), Fourier transforms infrared spectroscopy (FTIR), and ...scanning electron microscopy spectroscopy (SEM). The FTIR analysis does not provide clear evidence on the effect of the doping amount. All diffraction peaks were perfectly matched with the pure phase of
BaTiO
3
. The tetragonal distortion factor is smoothly dependent on the doping amount. The grains decrease in size when Tb concentration is increased. The diffusion coefficient and phase transitions do not change greatly when introducing Tb into the crystal. Fitting values of
γ
also support the evidence of normal ferro-paraelectric transition. Doped materials have a dielectric constant greater than undoped material, a meanwhile low loss is observed. The presence of Tb inhibits the formation of oxygen vacancies and promotes the stabilization of the oxygen-deficient system with the support of tetragonal phase formation during the sintering process.
Lu-doped SrBi2Ta2O9 (SrBi2-xLuxTa2O9 where x = 0, 0.025, 0.05, 0.75 and 0.1)
powders were synthesized by combination of molten salt method and
solid-state route. FTIR, Raman and XRD techniques were ...performed to follow
the transformation of reactants into the desired products. Characterization
of all samples shows pure and single-phase orthorhombic structured materials
obtained with plate-like morphology that is composed of fine and
coarse-grained particles. The prepared powders were pressed and sintered at
different temperatures up to 1200?C. Microstructure of the sintered samples
is also likely to be affected by doping. The first study of dielectric
measurements describes the effect of the application of DC bias, at
roomtemperature, on the undoped and Lu-doped ceramics and shows that there
is little or no effect of DC bias. The sample SrBi1.95Lu0.05Ta2O9 had
maximal dielectric constant (??) and minimal dielectric loss (tan?). In the
second part of this work, the temperature dependence of ?? and tan_ was
considered. It was concluded that Lu-doping not only reduces the Curie
temperature, but also brings a diffused phase transition, showing a
crossover between displacive and diffusive behaviour.
This work is devoted to the synthesis and characterization of yttrium-doped SrBi
2
Nb
2
O
9
ceramics prepared by three methods: solid state reaction, co-precipitation, and hydrothermal. Multiple ...characterizations, specifically scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR), were used to validate the structural feature. The crystallite size was estimated by Scherrer’s formula and the Williamson–Hall plot. The effect of the process on the band intensities of the FTIR spectra was investigated. The crystallite size and microstructure of ceramics prepared from different synthesis processes were strongly influenced by the sinterability. SEM images revealed nanograin ceramics for materials prepared by co-precipitation and hydrothermal methods and micrograin ceramics prepared by the solid state method. The synthesized compounds underwent phase transitions at 480–465°C. The dielectric and electrical properties of these Y-doped SrBi
2
Nb
2
O
9
ceramics appear to be dependent on the grain size.
Structure and dielectric properties of Eu-doped SrBi2Nb2O9 ceramics (with 0,
20 and 35 at.% of Eu), prepared by the solid-state method and sintering,
were investigated. XRD, FTIR and SEM measurements ...were provided to validate
the characteristic structural features of the obtained ceramics. For all
samples, the orthorhombic structure was identified through XRD analysis. SEM
results confirmed that the fabricated samples have relatively dense
structure with rod- and plate-like grains typical for Aurivillius layered
structures. Dielectric results showed that the doping with Eu decreases
dielectric constant and reduces dielectric loss. Movement of the dielectric
peak towards higher temperatures appearing at about 400?C with increase of
frequency indicates on relaxor behaviour of the sample with 35 at.% of Eu.
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