Synthesis and characterization of CaBi4Ti4O15 thin films annealed by microwave and conventional furnaces

CaBi₄Ti₄O₁₅ thin films were deposited by the polymeric precursor method and crystallized in a domestic microwave oven and conventional furnace. The films obtained for microwave energy are well-adhered, homogeneous and with good specularity when treated at 700 ^°C for 10 min. The microstructure and the structure of the films can be tuned by adjusting the crystallization conditions. When microwave oven is employed, the films presented bigger grains with mean grain size around 80 nm. For comparison, films were also prepared by the conventional furnace at 700 °C for 2 h.     

Theoretical analysis on the structure of Nb‐doped SrBi4Ti4O15

The structure of niobium‐doped SrBi₄Ti₄O₁₅ was calculated by using density function and discrete variation method (DFT–DVM). By comparing the total energy of different doping sites, the total energy is found to be lower when Nb ion was substituted into the Ti site in the upper perovskite layer, which is far from the two bismuth (Bi) ions in the perovskite layer. The bonding strength of Nb (3)‐O increases and the electronic conductivity of the SBT decreases after Nb doping. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

超高温压电陶瓷CaBi2Nb2O9的定向生长及性能

将熔盐法制备的片状CaBi2Nb2O9（CBNO）前驱体在1050℃烧结成陶瓷,对陶瓷晶粒取向和形貌进行了分析和表征,研究了其介电、铁电和压电性能.与传统固相法制备的样品相比较,新工艺制备出的CaBi2Nb2O9陶瓷,烧结温度降低,晶粒定向生长,具有明显织构特征,室温时极化变得容易,介电损耗减小,压电系数明显提高.     

Synthesis and dielectric properties of the Aurivillius oxide BaBi4Ti4O15 by the Pechini method

Barium bismuth titanate (BaBi₄Ti₄O₁₅, BBT) powders were synthesized using the Pechini method, and related ceramics were prepared using a solid-state reaction method. The structure and morphology of the BBT specimens were examined by the X-ray diffraction and scanning electron microscopy. Complexation of citric acid with metallic cations was detected by Fourier-transform infrared spectroscopy. Thermal analyses of the obtained gels were performed using differential thermal gravimetry. Pure BBT powders could be obtained at a relatively low temperature of 500 °C. A broad dielectric peak around Curie temperature and significant frequency diffusion of the maximum dielectric permittivity were observed. The diffuseness parameter was 1.82, and relaxation was attributed to cationic disordering at the A-site of BBT.     

Catalytic applications of mesoporous CaBi2O4 obtained from a single source precursor

Research on Chemical Intermediates - With the aim of generating mesoporous CaBi2O4 and further to investigate its catalytic properties, thermolysis of mineral beyerite was carried out between 650...     

Notable enlargement of remnant polarization for fatigue-free SrBi4Ti4O15 thin films by La-substitution

La-doped SrBi₄Ti₄O₁₅, SrBi_4–x La _x Ti₄O₁₅ (SBLT-x, x = 0.00, 0.10 and 0.25), thin films have been successfully prepared by the sol–gel method. Structures, surface morphology and ferroelectric properties were investigated. Compared with undoped SBTi, SBLT-0.10 shows a notable larger remnant polarization (2P _r = 46 μC/cm²). Meanwhile, the SBLT-0.10 film shows little change of P _nv and −P _nv up to 4.4 × 10¹⁰ switching cycles, suggesting an excellent fatigue-endurance characteristics.     

Quantitative WDXS Microanalysis of Bismuth-Based BaBi4Ti4O15 Perovskites Doped with Nb and Fe

 Quantitative electron-probe microanalysis was used to determine the chemical composition of an Fe- and Nb-doped bismuth-based BaBi₄Ti₄O₁₅ perovskite compound. Elemental concentrations of Fe, Nb, Bi, Ba and Ti were accurately measured using wavelength-dispersive X-ray spectroscopy that was optimised for the analysis of a complex oxide matrix containing minor concentrations of dopants. Measurements were performed with a JEOL JXA 840A electron probe microanalyser at 20 and 26 kV, 50 nA beam current, 100 s maximum counting time and 0.3% preset counting deviation (σ_c) using both PET and LiF crystals. K-ratios were quantified by the ZAF and the φ(ρz) PAP matrix-correction procedures. The results showed that dopants incorporate into the BaBi₄Ti₄O₁₅ at Ti^4 + sites according to the Ba_1−4XBi_4 + 4XTi_4−4XFe_4XO₁₅ and Ba_1 + 4XBi_4−4XTi_4−4XNb_4XO₁₅ solid-solution formulae. The majority of the excess charge introduced by the substitution of Ti^4 + with Fe^3 + or Nb^5 + is compensated for the change in the Ba^2 +/Bi^3 + ratio.     

Atomic Simulations of Aurivillius Oxides: Bi3TiNbO9, Bi4Ti3O12, BaBi4Ti4O15 and Ba2Bi4Ti5O18 Doped with Pb,Al, Ga,In, Ta

The Aurivillius oxides were originally of interest for their ferroelectric properties and have recently been explored in the field of oxide ion conductivity. Atomistic simulation methods have been carried out for Bi₃TiNbO₉, Bi₄Ti₃O₁₂, BaBi₄Ti₄O₁₅ and Ba₂Bi₄Ti₅O₁₈ doped with Pb, Al, Ga, In, Ta to determine defect energy in the materials by employing efficient energy minimization procedures. The calculations rest upon the specification of an interatomic potential model, which expresses the total energy of the system as a function of the nuclear coordinates. The Born model framework, which partitions the total energy into long‐range Coulombic interactions and a short‐range term to model the repulsions and van der Waals forces between electron charge clouds, is employed. This is embodied in the GULP simulation code. Dopant solution energy versus ion size trends are found for both isovalent and aliovalent dopant incorporation at Bi and Ta sites. Trivalent dopants (Al, Ga, In) and Pb are more favorable on the Bi site, whereas Ta dopants preferentially occupy the Ti site.     

La_2Ti_6O_(15)-CeTi_(21)O_(38)-PbTiO_3 ceramics formed in gaseous penetration of La-Ce into PbTiO_3 and their electric properties

PbTiO3 ceramics, which are typical ferroelectric materials, are useful in various applied fields. For example, it has a very good candidacy for piezoelectric materials for high temperature and high sensibility. In recent years, the studies on doped PbTiO3 ceramics have received consid-erable attention[1—3]. The modified PbTiO3 ceramics doped with Ca2+, Sm3+, Y3+, Ce4+ etc. have some better properties: their Curies temperature decreases, their tetragonal distortion degree de-grades and th…     

Temperature Dependence of the Electrical Properties of Na2Ti3O7/Na2Ti6O13/POMA Composites

The temperature dependence of the electrical properties of composites formed by biphasic sodium titanate and poly(o-methoxyaniline) (Na₂Ti₃O₇/Na₂Ti₆O₁₃/POMA) with different concentrations of POMA (0%, 1%, 10%, 15%, 35% and 50%) in the ceramic matrix was determined from measurements of complex impedance. The structural details were studied by means of X-ray diffraction, confirming the formation of the Na₂Ti₃O₇/Na₂Ti₆O₁₃/POMA composites. The displacement of the (200) reflection from 2θ = 10.45° to 11.15° in the composites with 10 and 15% of POMA suggested the partial replacement of H⁺ for Na⁺ in the Na₂Ti₃O₇ structure. The thermal properties were investigated by Thermogravimetry and Differential Thermal Analysis. The Thermogravimetry curves of the composites with POMA content of 1, 10 and 15% presented profiles similar to that of pure sodium titanate sample. The composites with 35 and 50% of POMA showed a process at temperatures around 60–70 °C, which was associated with water absorbed by the polymer. The analysis of the complex impedance spectroscopy measurements revealed that the electrical resistivity of the composites in the range from 0 to 35% increased by two orders of magnitude, with different values for each concentration. This positive temperature coefficient of resistivity was less noticeable in the composite with highest POMA mass content (50%). The rapid increase in resistivity caused an increase in the relaxation time calculated from the time domain. The electrical response of the 50% of POMA compound changes in relation to what was observed in the other compounds, which suggests that there is a saturation limit in the increase in resistivity with POMA content.     

Spin-canting and magnetic anisotropy in ultrasmall CoFe2O4 nanoparticles

The magnetic properties of cobalt ferrite nanoparticles dispersed in a silica matrix in samples with different concentrations (5 and 10 wt% CoFe2O 4) and same particle size (3 nm) were studied by magnetization, DC and AC susceptibility, and Mossbauer spectroscopy measurements. The results indicate that the particles are very weakly interacting. The magnetic properties (saturation magnetization, anisotropy constant, and spin-canting) are discussed in relation to the cation distribution.     

Impedance and electric modulus approaches to investigate four origins of giant dielectric constant in CaCu3Ti4O12 ceramics

The frequency dependence of electric modulus of polycrystalline CaCu₃Ti₄O₁₂ (CCTO) ceramics has been investigated. The experimental data have also been analyzed in the complex plane of impedance and electric modulus, and a suitable equivalent circuit has been proposed to explain the dielectric response. Four dielectric responses are first distinguished in the impedance and modulus spectroscopies. The results are well interpreted in terms of a triple insulating barrier capacitor model. Using this model, these four dielectric relaxations are attributed to the domain, domain-boundary, grain-boundary, and surface layer effects with three Maxwell–Wagner relaxations. Moreover, the values of the resistance and capacitance of bulk CCTO phase, domain-boundary, grain-boundary and surface layer contributions have been calculated directly from the peak characteristics of spectroscopic plots.     

Synthese und Kristallstruktur von Ba4,5Ca1,5La2Fe4O15, Ba5CaEu2Fe4O15 und Ba5CaNd2Co4O15

Synthesis and Crystal Structure of Ba_4.5Ca_1.5La₂Fe₄O₁₅, Ba₅CaEu₂Fe₄O₁₅ and Ba₅CaNd₂Co₄O₁₅ The compounds (I) Ba_4.5Ca_1.5La₂Fe₄O₁₅, (II) Ba₅CaEu₂Fe₄O₁₅ and (III) Ba₅CaNd₂Co₄O₁₅ were prepared and investigated by single crystal X-Ray technique. They belong to the Ba₆Nd₂Al₄O₁₅ typ, space group C? P6₃mc, (I): a = 11.677, c = 6.959 Å; (II): a = 11.570, c = 6.892 Å; (III): a = 11.604, c = 6.839 Å, Z = 2. The crystal chemistry of these substances will be discussed.     

New cubic perovskite Na(Cu2.5Ti0.5)Ti4O12 with square planar coordination of Ti4+

A new perovskite, Na[Cu(2.5)Ti(0.5)]Ti4O12, has been synthesized using a conventional solid-state technique. Neutron and synchrotron X-ray powder diffraction studies in combination with density measurements and bond-valence calculations have revealed that the material crystallizes in the cubic Im space group (a = 7.38472(2) A, Z = 2) with the square-plane site accommodating 16.7% of Ti4+. This is the highest level of non-Jahn-Teller cation substitution for Cu2+ reported to date for CaCu3Ti4O12-type perovskites prepared at ambient pressure.     

ZrSn0,5Ti0,5O4 als Wirtsstruktur für keramische Farbkörper Strukturuntersuchungen an ZrTiO4 und ZrSn0,5Ti0,5O4

ZrSn_0.5Ti_0.5O₄ as a Matrix for Ceramic Colours. Structural Investigations on ZrTiO₄ and ZrSn_0.5Ti_0.5O₄ ZrSn_0.5Ti_0.5O₄ and ZrTiO₄ crystallize in Pbcn having the lattice constants a = 481.45(10), b = 559.61(11), c = 510.50(9) pm and a = 478.55(13), b = 547.55(12), c = 502.77(14) pm, respectively. Their crystal structures have been solved and refined using single crystal data. According to the structural data derived in this work ZrTiO₄ possesses α-PbO₂ type of structure with Zr and Ti randomly distributed over the cation sites. ZrSn_0.5Ti_0.5O₄ is isostructural. As compared to ZrTiO₄ the metal-oxygen bond lengths in ZrSn_0.5Ti_0.5O₄ are increased. By substituting M⁴⁺ by In³⁺ (RE³⁺) and V⁵⁺ bright yellow pigments have been obtained.     

Mechanism of Formation of Bi4Ti3O12

The mechanism of solid-phase reaction of Bi₄Ti₃O₁₂ formation was studied. Formation of the layered perovskite-like bismuth titanate occurs via intermediates with sequential changes in the coordination polyhedron of bismuth. A correlation is analyzed between the temperature of the onset of activation of the solid-phase reaction and the melting point of the surface (intergrain) phase based on bismuth oxide.