“…To determine the activation energy ( E a ) involved in the dielectric relaxation process of the BFMO ceramics, the temperature dependence of the angular frequency ( ω m ) is fitted by the Arrhenius law 55 : where ω 0 is the pre‐exponential factor, E a is activation energy, and k B and T have their normal meanings. The Arrhenius law fitting the plot of Ln ω m versus 1000/ T (Figure S2f) yielded the E a value of 1.01 eV, which is almost the same value ( E a ∼ 1.0 eV) reported for the doubly ionized 56 . The ionization of can generate conducting electrons via the following reaction 49 : …”
Section: Resultssupporting
confidence: 70%
“…The Arrhenius law fitting the plot of Lnω m versus 1000/T (Figure S2f) yielded the E a value of 1.01 eV, which is almost the same value (E a ∼ 1.0 eV) reported for the doubly ionized 𝑉 ö. 56 The ionization of 𝑉 ö can generate conducting electrons via the following reaction 49 :…”
We report microstructures and physical (dielectric, magnetic, and optical) properties of sol-gel derived Ba 2 FeMnO 6 (BFMO) double perovskite powders. The BFMO powders belong to hexagonal crystal structure with P-6m2 space group. SEM images reveal the powders are nearly homogeneous distribution with spherical morphology and average particle size of 300 nm. Energy-dispersive spectra gave out the molar ratio of the Ba:Fe:Mn elements equal to 2.16:1.00:1.00.FTIR spectrum verified the [FeO 6 ] and [MnO 6 ] octahedra present in the powders. X-ray photoelectron spectroscopy spectra identified the chemical valence states of the constituent elements. The BFMO ceramics displayed a strong frequency dispersion dielectric behavior. A relaxor-like dielectric behavior appeared around ∼475 K due to the contributions of oxygen vacancies of(𝑉 ö) and the (Fe ′ Mn −)∕(Mn ′ Fe −) defect dipoles. A ferrimagnetic behavior was observed in the powders at 5 K with M S = 0.14 μ B /f.u. and H C = 1.51 kOe. The magnetic Curie temperature (T C ) was 381 K, whereas the Neel temperature (T N ) was 31 K. The ferrimagnetic behavior is governed by the Mn 3+ -Fe 4+ double-exchange interaction via the mediated oxygen between them. The BFMO powders have a direct optical bandgap of 1.65 eV, which originates from the electron transferring from O 2p to Mn 3d (and/or Fe 3d) levels. The unique combination of high temperature ferrimagnetism and semiconductivity in the BFMO powders makes them particularly appealing for magnetic spintronics and photovoltaics.
“…To determine the activation energy ( E a ) involved in the dielectric relaxation process of the BFMO ceramics, the temperature dependence of the angular frequency ( ω m ) is fitted by the Arrhenius law 55 : where ω 0 is the pre‐exponential factor, E a is activation energy, and k B and T have their normal meanings. The Arrhenius law fitting the plot of Ln ω m versus 1000/ T (Figure S2f) yielded the E a value of 1.01 eV, which is almost the same value ( E a ∼ 1.0 eV) reported for the doubly ionized 56 . The ionization of can generate conducting electrons via the following reaction 49 : …”
Section: Resultssupporting
confidence: 70%
“…The Arrhenius law fitting the plot of Lnω m versus 1000/T (Figure S2f) yielded the E a value of 1.01 eV, which is almost the same value (E a ∼ 1.0 eV) reported for the doubly ionized 𝑉 ö. 56 The ionization of 𝑉 ö can generate conducting electrons via the following reaction 49 :…”
We report microstructures and physical (dielectric, magnetic, and optical) properties of sol-gel derived Ba 2 FeMnO 6 (BFMO) double perovskite powders. The BFMO powders belong to hexagonal crystal structure with P-6m2 space group. SEM images reveal the powders are nearly homogeneous distribution with spherical morphology and average particle size of 300 nm. Energy-dispersive spectra gave out the molar ratio of the Ba:Fe:Mn elements equal to 2.16:1.00:1.00.FTIR spectrum verified the [FeO 6 ] and [MnO 6 ] octahedra present in the powders. X-ray photoelectron spectroscopy spectra identified the chemical valence states of the constituent elements. The BFMO ceramics displayed a strong frequency dispersion dielectric behavior. A relaxor-like dielectric behavior appeared around ∼475 K due to the contributions of oxygen vacancies of(𝑉 ö) and the (Fe ′ Mn −)∕(Mn ′ Fe −) defect dipoles. A ferrimagnetic behavior was observed in the powders at 5 K with M S = 0.14 μ B /f.u. and H C = 1.51 kOe. The magnetic Curie temperature (T C ) was 381 K, whereas the Neel temperature (T N ) was 31 K. The ferrimagnetic behavior is governed by the Mn 3+ -Fe 4+ double-exchange interaction via the mediated oxygen between them. The BFMO powders have a direct optical bandgap of 1.65 eV, which originates from the electron transferring from O 2p to Mn 3d (and/or Fe 3d) levels. The unique combination of high temperature ferrimagnetism and semiconductivity in the BFMO powders makes them particularly appealing for magnetic spintronics and photovoltaics.
“…For PLT20 and PLT32 ceramic, activation energies are about 1.73 and 1.75 eV respectively. For all compositions, values of activation energies are very close to OVs related high temperature dielectric relaxations in perovskite systems, such as: SrTiO 3
44 , (PbLa)(Zr 0.9 Ti 0.1 )O 3
45 , and (Pb,Cd,La)TiO 3 ceramics 42 .Figure 4Normalized imaginary parts Z ″ /Z ″ max of impedance as a function of frequencies for ( a ) PLT20, ( b ) PLT24, ( c ) PLT28 and ( d ) PLT32 ceramics.Figure 5ln ω versus 1000/T curves for PLT ceramics, straight lines are used to fit the Arrhenius law.
…”
Section: Resultssupporting
confidence: 57%
“…1, it is found that abnormal dielectric peaks in permittivity and loss are observed (higher temperature region), similar behaviours are also reported in other perovskites (10–10 7 Hz, 400–800 °C), which are called dielectric relaxation 38–41 . In order to give a clear knowledge of high temperature dielectric relaxations, impedance technology is selected as an efficient technique, which has been intensive used in electrical properties of electro-ceramic materials 42 . The variation of normalized imaginary parts of impedance ( Z ″/ Z ″ max ) are shown in Fig.…”
The unique properties and great variety of relaxer ferroelectrics make them highly attractive in energy-storage and solid-state refrigeration technologies. In this work, lanthanum modified lead titanate ceramics are prepared and studied. The giant electrocaloric effect in lanthanum modified lead titanate ceramics is revealed for the first time. Large refrigeration efficiency (27.4) and high adiabatic temperature change (1.67 K) are achieved by indirect analysis. Direct measurements of electrocaloric effect show that reversible adiabatic temperature change is also about 1.67 K, which exceeds many electrocaloric effect values in current direct measured electrocaloric studies. Both theoretical calculated and direct measured electrocaloric effects are in good agreements in high temperatures. Temperature and electric field related energy storage properties are also analyzed, maximum energy-storage density and energy-storage efficiency are about 0.31 J/cm3 and 91.2%, respectively.
“…Fora ll compositions, the valueso ft he activation energies were very close to those for OV-induced high-temperature relaxation behaviors in perovskite systems,s uch as SrTiO 3 , [15] (PbLa)(Zr 0.9 Ti 0.1 )O 3 , [37] and (Pb,Cd,La)TiO 3 ceramics. [38] It is well known that dielectric relaxation phenomena induced by OVss hould be quantitatively similar regardless of the kind of perovskite oxides,b ecause they have the same relaxation mechanism. [8,15,32] Thev alue of E a is also dependent on the concentration of OVs: E a = 0eVf or stoichiometric ABO 2.8 , 0.5 eV for ABO 2.9 ,1 .0 eV for ABO 2.95 ,a nd 2.0 eV for ABO 3 .…”
Section: High-temperature Relaxation Of Pszt Ceramicsmentioning
(1−x)PbZrO3–xSrTiO3 (x: 10, 20, and 30 mol %) ceramics were prepared by a conventional mixed‐oxide solid‐state reaction method. The relaxer behaviors of the PbZrO3–SrTiO3 ceramics were examined in the temperature range of 120–523 K. A broad dielectric maximum that shifted to higher temperature with increasing frequency signified the relaxer‐type behaviors of these ceramics. The value of the relaxation parameter of γ=1.73, estimated from the linear fit of the modified Curie–Weiss law, indicated the relaxer nature. High‐temperature dielectric relaxation phenomena were found in the temperature region of 600‐850 K. The activation energy, calculated from impedance measurements of samples, suggested that the dielectric relaxation was a result of oxygen vacancies generated during the sintering process. The energy‐storage density calculated from hysteresis loops reached about 0.46 J cm−3 for the PSZT30 ceramic at room temperature.
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