ABO3-type Perovskite Structure Research Articles

Analysis of Ba(Mg1/3, Ta2/3)O3 by atomic-resolution scanning transmission electron microscopy

The crystal structure of Ba(Mg1/3, Ta2/3)O3, which is thought to contribute to its microwave properties, was analyzed at the atomic resolution using scanning transmission electron microscopy (STEM). Using STEM, Ba(Mg1/3, Ta2/3)O3 exhibits an ABO3-type perovskite structure observed in the [110] direction with two structures identified: a disordered region, in which Mg and Ta atoms randomly occupy the B site, and an ordered region, in which Mg and Ta atoms are ordered. In the disordered region, the displacement directions of the Ba∣O and Mg/Ta atomic columns were random, whereas in the ordered region, the displacement directions of the Ba∣O and Mg atomic columns were random. The Ta atomic columns were displaced toward the neighboring Mg atomic columns. This structural change may affect the microwave properties of Ba(Mg1/3, Ta2/3)O3.

Size effect of PbTiO3 on its charge separation ability

PbTiO3 (PTO) is a ferroelectric oxide with a typical ABO3-type perovskite structure. However, the majority of prior research has concentrated on the PTO material preparation process, making the correlation between heteroatom doping and the piezoelectric effect superior. It is also worthwhile to pay attention to its internal mechanism and the size effect of the redesigned interface, which will result in many fresh experimental occurrences. In this work, first-principles methods were used to investigate the crystal geometry, electronic structure, electrical characteristic, and surface charge transfer of monolayer as well as multilayer PTO in order to understand the origin of significant size effect. Only the 1̅10 crystal plane has a considerable size effect in contrast to other crystal planes, and its energy gap is correlated with the thickness of its layers, according to our research. The energy gap consistently shrinks as size and thickness grow. The findings demonstrate that PTO can change from a semiconductor to a metal due to the size effect. And the increase in the dielectric silica coating can promote the separation of surface charge by enhancing the polarization characteristics of the exposed oxygen atom of PTO. Our research not only clarifies the process of charge separation brought on by the different PTO size, but it also offers a suggestion for investigating the interfacial interactions of more ABO3-type perovskite-structured semiconductor materials.

Enhanced dielectric, ferroelectric, and ferromagnetic properties of 0.7Bi1−xTmxFeO3–0.3BaTiO3 ceramics by Tm-induced structural modification

In this study, Tm-doped 0.7Bi1−xTmxFeO3–0.3BaTiO3 (x = 0–0.05) ceramics have been fabricated using traditional solid-phase reactions and their structural, morphological, and dielectric as well as multiferroic properties are investigated. X-ray diffraction and Rietveld refinement indicated the formation of a Tm-modulated morphotropic phase boundary (MPB) from the rhombohedral (R3c) and tetragonal (P4mm) phases to a single P4mm phase for Tm content of x = 0.02–0.03. Tm occupation of lattice sites is strongly suggested at both the A and B sites in the ABO3-type perovskite structure, which is supported by the obtained Raman spectra, the calculated tolerance factor, and dielectric relaxation characteristics. With the Tm-induced aforementioned–structural modification, the dielectric constant, remnant polarization (Pr), and remnant magnetization (Mr) values indicate that the dielectric and multiferroic properties are greatly improved. The obtained maximum remnant polarization (2Pr = 35.28 μC/cm2) and remnant magnetization (2Mr = 0.56 emu/g) are approximately two and seven times larger, respectively, than those of the sample without Tm substitution (x = 0). With increasing the Tm content, the remnant polarization, and the remnant magnetization exhibit almost the same trends in variation, indicating the possible existence of a relatively strong magnetoelectric coupling effect. Our study may provide a substitution strategy (structural modification by substituting the same element into two different lattice sites) to efficiently enhance the dielectric and multiferroic properties of BiFeO3–BaTiO3-based ceramics.

Effects of A-site cations and the substitution site on the upconversion luminescence of Er3+ in the zirconate perovskite series

We investigated the upconversion luminescence (UCL) properties of AZrO3 (A = Ca, Sr, and Ba) perovskite compounds co-doped with Er3+ and Yb3+ in relation to the change in the crystal structure from orthorhombic to cubic. The dopants selectively substituted the A- and B-site ions in the ABO3-type perovskite structure. Upon excitation at 980 nm, we observed the two main UCL features at 545 nm and 660 nm, which depended strongly on the ion occupying the A-site and whether the dopant substituted the ion occupying the A- or the B-site. The intensity of the UCL was found to be maximized for A = Ca because this ion resulted in the lowest crystal symmetry of the host material. The dependence of the UCL on the substitution site (A or B) was significant for A = Sr, in accordance with the sizable difference in the lattice constants of host materials doped at either the A-site or B-site. Our results showed that the crystal symmetry of the host materials and the related local lattice symmetry could play an important role in determining the emission properties of Er3+ ions in perovskite crystals.

Influence of the Perovskite La0.8Sr0.2Mn0.5Co0.5O3-δ on the Electrochemical Performance of the Graphene-Based Supercapacitor

A supercapacitor is a potential energy system that will be a part of an efficient storage device of renewable energy, such as a small battery and a large energy storage system (ESS), etc. However, a lot of efforts have been devoted to improving stability. Generally, ABO3-type perovskite structure has been studied as an electrode and/or an oxide ion-conducting electrolyte for solid oxide fuel cells with stable structural stability at high temperatures. In this study, perovskite material (La0.8Sr0.2Mn0.5Co0.5O3-δ. LSMCO) was added as a component of the supercapacitor electrode for enhanced stability. According to electrochemical measurements, at 5 mV/s, the specific capacitance of the graphene-based electrode (G95) is 68 F/g, and the electrode mixed with perovskite (G70L25) is 55 F/g. Nonetheless, the standard deviation of the capacitance value of G70L25 is smaller than that of G95. Alongside this, the G70L25 electrode showed that specific capacitance decreased in the cycling test, but, for the G95 electrode, the specific capacitance after the 4990th cycle increased or decreased, resulting in unpredictable results. Therefore, perovskite added electrode (G70L25) shows higher stability compared to the graphene nanoplatelets electrode (G95) in both initial and cycling performance, albeit a lower specific capacitance.

Atomic structure stabilization in BiFeO3 thin film by Mn doping

This study experimentally investigated the atomic structure of a single-crystalline Mn-doped BiFeO3 (BFO) thin film using X-ray fluorescence holography with synchrotron radiation. Bi atoms can be reconstructed from both Fe Kβ and Mn Kα fluorescence X-ray holograms, indicating Mn doping at B sites in ABO3-type perovskite structure. The fluorescence intensity of the 1st to 4th nearest Bi atoms around target Fe atoms was lower than those around Mn atoms, confirming the selective formation of Bi vacancies around Fe atoms. In contrast, the 5th to 8th nearest Bi atoms around Fe atoms showed higher intensities than those around Mn atoms, indicating that the Mn-doped BFO thin film had a double-perovskite-like structure. These results provide important information that helps elucidate the mechanism by which Mn doping modifies the conductivity of BFO.

Effect of B-site doping on electrical conductivity of YAlO3 based electrolytes for solid oxide fuel cells

Solid oxide fuel cells (SOFCs) have emerged as high temperature fuel cell technology operating at temperatures around 1000 °C. Lowering the operating temperature enables the use of cheaper materials while maintaining high power outputs. Electrolytes with ABO3-type perovskite structure are good ionic conductors and are promising materials for SOFCs. In this study, a systematic investigation on the synthesis and characterization of Mg- substituted YAlO3 system has been performed. The samples have been synthesized by wet chemical citrate gel route and the electrical conductivity measurements have been conducted in air between 300 and 800 °C. Effect of composition of the phases on total conductivity has been analyzed employing X-ray diffraction. The influence of microstructure on total conductivity has been studied using scanning electron microscopy and orientation imaging microscopy.

Synthesis and characterization of lanthanum- and yttrium-doped Fe2O3 pigments

Iron oxide has been doped with rare earth ions (yttrium or lanthanum) aiming at producing ceramic pigments with hues that vary from orange to brown. The powders were synthesized from polymeric precursors using the Pechini method and subsequently calcined between 900 and 1100 ºC. The resulting pigments were characterized by BET, X ray diffraction, colorimetric analysis, UV-visible, infrared (FTIR), particle size distribution and thermal analysis. The color depicted by La/Fe powders changed as the calcination temperature increased from 900 ºC to 1100 ºC, as established by the corresponding changes in the values of the colorimetric coordinates from L* a* b* = 49.003, 10.541, 12.609 to L* a* b* = 31.279, 6.096, 6.877. On the other hand, Y/Fe powders were little affected by similar changes in the calcination temperature, revealing the effect of yttrium on the color stability of the powder. The values of the colorimetric coordinates in this case varied from L* a* b* = 45.230, 17.315, 28.750 to L* a* b* =51.631, 15.726, 25.825. Structural changes were also noticed as a function of the size of the rare earth ion added to the structure. Upon calcination at 900°C, lanthanum stabilized the ABO3-type perovskite structure whereas the presence of yttrium resulted in a mixture of oxides.

Photophysical and Photocatalytic Properties of MIn0.5Nb0.5O3 (M = Ca, Sr, and Ba)

New photocatalysts MIn0.5Nb0.5O3 (M = Ca, Sr, and Ba) with the ABO3 type perovskite structure in which B sites are occupied by In3+ or Nb5+ ions randomly in a charge-balanced manner were synthesized. They were characterized by structural analysis, diffuse reflectance spectroscopy, and photocatalytic activity measurement in evolving H2 and O2 from pure water with cocatalysts Pt and NiOx under UV and visible light irradiation (λ > 420 nm), respectively. It is suggested that the conduction bands of these photocatalysts are composed of In 5s and Nb 4d levels, and the valence bands are composed of O 2p levels. With the decrease of the ionic radius in the A site, the CaIn0.5Nb0.5O3, SrIn0.5Nb0.5O3, and BaIn0.5Nb0.5O3 photocatalysts show different photocatalytic activities. Under UV light irradiation, the BaIn0.5Nb0.5O3 photocatalyst powder with cocatalyst NiOx split pure water into H2 and O2 in a nearly stoichiometric ratio. Under visible irradiation, all of these photocatalysts show obvious photocatalytic activity in evolving H2 from pure water with cocatalyst NiOx.