scholarly journals Experimental and theoretical studies on induced ferromagnetism of new (1 − x)Na0.5Bi0.5TiO3 + xBaFeO3−δ solid solution

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Dang Duc Dung ◽  
Nguyen Huu Lam ◽  
Anh Duc Nguyen ◽  
Nguyen Ngoc Trung ◽  
Nguyen Van Duc ◽  
...  
Keyword(s):  
Solid Solution ◽  
Density Functional ◽  
Room Temperature Ferromagnetism ◽  
Sol Gel ◽  
Density Functional Theory Calculations ◽  
Ferroelectric Materials ◽  
Crystal Field Theory ◽  
Simple Method ◽  
Teller Distortion ◽  
Jahn Teller

AbstractNew solid solution of Na0.5Bi0.5TiO3 with BaFeO3−δ materials were fabricated by sol–gel method. Analysis of X-ray diffraction patterns indicated that BaFeO3−δ materials existed as a well solid solution and resulted in distortion the structure of host Na0.5Bi0.5TiO3 materials. The randomly incorporated Fe and Ba cations in the host Na0.5Bi0.5TiO3 crystal decreased the optical band gap from 3.11 to 2.48 eV, and induced the room-temperature ferromagnetism. Our density-functional theory calculations further suggested that both Ba for Bi/Na-site and Fe dopant, regardless of the substitutional sites, in Na0.5Bi0.5TiO3 lead to the induced magnetism, which is illustrated in terms of the exchange splitting between spin subbands through the crystal field theory and Jahn–Teller distortion effects. Our work proposes a simple method for fabricating lead-free ferroelectric materials with ferromagnetism property for multifunctional applications in smart electronic devices.

Electronic Structures in LaTiO3/LaAlO3 Multilayers

2013 ◽  
Vol 771 ◽  
pp. 7-11 ◽  
Author(s):  
Er Jun Kan
Keyword(s):  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Density Functional ◽  
Orbital Ordering ◽  
Crystal Field Theory ◽  
Teller Distortion ◽  
Jahn Teller ◽  
Important Direction ◽  
Jahn Teller Distortion

We demonstrate the existence of a hidden degree of freedom controlling the orbitalordering in [LaTiO1/[LaAlO5 multilayers with comprehensive density-functional theorycalculations. The orbitals of two-dimensional (2D) 3d1state of Ti atoms in the multilayers alwayscontain large dxy components, which is unexpected from crystal field theory (first Jahn-Tellerdistortion). The competition between first and second Jahn-Teller distortion induces variousmagnetic properties. Thus, transition-metal oxides/non-transition-metal oxides multilayers mayprovide an important direction to manipulate the spin and orbital ordering in magnetic materials.

scholarly journals Anion-Regulated Synthesis of ZnO 1D Necklace-Like Nanostructures with High Photocatalytic Activity

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Xiaoyun Qin ◽  
Dongdong Shi ◽  
Bowen Guo ◽  
Cuicui Fu ◽  
Jin Zhang ◽  
...  
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
High Photocatalytic Activity ◽  
Simple Method ◽  
Functional Theory ◽  
Photocatalytic Ability ◽  
New Ideas ◽  
Subsequent Calcination ◽  
Grain Surface ◽  
Hexagonal Nanoplates

Abstract One-dimensional (1D) nanomaterials with specific architectures have received increasing attention for both scientific and technological interests for their applications in catalysis, sensing, and energy conversion, etc. However, the development of an operable and simple method for the fabrication of 1D nanostructures remains a challenge. In this work, we developed an “anion-regulated morphology” strategy, in which anions could regulate the dimensionally-restricted anisotropic growth of ZnO nanomaterials by adjusting the surface energy of different growth facets. ZnO 1D necklace-like nanostructures (NNS) could be prepared through a hydrothermal treatment of zinc acetate and urea mixture together with a subsequent calcination procedure at 400 °C. While replacing the acetate ions to nitrate, sulfate, and chlorion ions produced ZnO nanoflowers, nanosheets and hexagonal nanoplates, respectively. Density functional theory calculations were carried out to explain the mechanism behind the anions-regulating anisotropic crystal growth. The specified ZnO 1D NNS offered improved electron transport while the grain surface could supply enlarged specific surface area, thus providing advanced photocatalytic ability in the following photodegradation of methyl orange (MO). Among the four photocatalysts with different morphologies, ZnO 1D NNS, possessing the highest catalytic activity, degraded 57.29% MO in the photocatalytic reaction, which was 2 times, 10 times and 17 times higher than nanoflowers, nanosheets and hexagonal nanoplates, respectively. Our work provides new ideas for the construction and application of ZnO 1D nanomaterials.

scholarly journals Enhanced Cycling Stability through Erbium Doping of LiMn2O4 Cathode Material Synthesized by Sol-Gel Technique

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1558 ◽  
Author(s):  
Hongyuan Zhao ◽  
Xiuzhi Bai ◽  
Jing Wang ◽  
Dongdong Li ◽  
Bo Li ◽  
...  
Keyword(s):  
Spinel Structure ◽  
Sol Gel ◽  
Reversible Capacity ◽  
Narrow Particle Size Distribution ◽  
Substantial Impact ◽  
Teller Distortion ◽  
Er Doping ◽  
Jahn Teller ◽  
Limn2o4 Cathode ◽  
Jahn Teller Distortion

In this work, LiMn2−xErxO4 (x ≤ 0.05) samples were obtained by sol-gel processing with erbium nitrate as the erbium source. XRD measurements showed that the Er-doping had no substantial impact on the crystalline structure of the sample. The optimal LiMn1.97Er0.03O4 sample exhibited an intrinsic spinel structure and a narrow particle size distribution. The introduction of Er3+ ions reduced the content of Mn3+ ions, which seemed to efficiently suppress the Jahn–Teller distortion. Moreover, the decreased lattice parameters suggested that a more stable spinel structure was obtained, because the Er3+ ions in a ErO6 octahedra have stronger bonding energy (615 kJ/mol) than that of the Mn3+ ions in a MnO6 octahedra (402 kJ/mol). The present results suggest that the excellent cycling life of the optimal LiMn1.97Er0.03O4 sample is because of the inhibition of the Jahn-Teller distortion and the improvement of the structural stability. When cycled at 0.5 C, the optimal LiMn1.97Er0.03O4 sample exhibited a high initial capacity of 130.2 mAh g−1 with an excellent retention of 95.2% after 100 cycles. More significantly, this sample showed 83.1 mAh g−1 at 10 C, while the undoped sample showed a much lower capacity. Additionally, when cycled at 55 °C, a satisfactory retention of 91.4% could be achieved at 0.5 C after 100 cycles with a first reversible capacity of 130.1 mAh g−1.

scholarly journals Controlling the Lithium Intercalation Voltage in the Li(Mn1-xNix)2O4 Spinel via Tuning of the Ni Concentration: a Density Functional Theory Study

2021 ◽  
Vol 74 ◽  
Author(s):  
Kemeridge T. Malatji ◽  
David Santos-Carballal ◽  
Umberto Terranova ◽  
Phuti E. Ngoepe ◽  
Nora H. de Leeuw
Keyword(s):  
Solid Solution ◽  
Density Functional Theory ◽  
Cathode Material ◽  
Lithium Ion Batteries ◽  
Density Functional ◽  
Lithium Ion ◽  
Lithium Intercalation ◽  
Functional Theory ◽  
Teller Distortion ◽  
Wide Range

ABSTRACT LiMn2O4 spinel is a promising cathode material for secondary lithium-ion batteries. Despite showing a high average voltage of lithium intercalation, the material is structurally unstable, undergoing lowering of the crystal symmetry due to Jahn-Teller distortion of the six-fold Mn3+ cations. Although Ni has been proposed as a suitable substitutional dopant to improve the structural stability of LiMn2O4 and enhance the average lithium intercalation voltage, the thermodynamics of the Ni incorporation and its effect on the electrochemical properties of this spinel material are not yet known. In this work, we have employed density functional theory calculations with a Hubbard Hamiltonian (DFT+u) to investigate the thermodynamics of cation mixing in the Li(Mn1_xNix)2O4 solid solution. Our results suggest LiMn1.5Ni0.5O4 is the most stable composition from room temperature up to at least 1000 K, in agreement with experiments. We also found that the configurational entropy is much lower than the maximum entropy at 1000 K, indicating that higher temperatures are required to reach a fully disordered solid solution. A maximum average lithium intercalation voltage of 4.8 eV was calculated for the LiMn1.5Ni0.5O4 composition, which is very close to the experimental value. The temperature was found to have a negligible effect on the Li intercalation voltage of the most stable composition. The findings reported here support the application of LiMn1.5Ni0.5O4 as a suitable cathode material for lithium-ion batteries, with a highly stable voltage of intercalation under a wide range of temperatures. Keywords: Spinel, equilibrium concentration, mixing thermodynamics, solid-state chemistry and lithium voltage of intercalation.

Structural, Optical and Magnetic Properties of (1−x)Bi0.5Na0.5TiO3+xBaCoO3−δ Solid Solution Systems Prepared by the Sol–Gel Method

2021 ◽  
Vol 21 (4) ◽  
pp. 2604-2612
Author(s):  
Dang Duc Dung ◽  
Nguyen The Hung
Keyword(s):  
Solid Solution ◽  
Magnetic Properties ◽  
Sol Gel ◽  
Host Lattice ◽  
Ferroelectric Materials ◽  
X Ray Diffraction ◽  
Gel Method ◽  
Sol Gel Method ◽  
Lattice Materials ◽  
Rhombohedral Symmetry

A new solid solution, (1−x)Bi0.5Na0.5TiO3+xBaCoO3−δ materials, was fabricated using the sol–gel method. X-ray diffraction showed that the crystal structure of the compound exhibited rhombohedral symmetry and is similar to the crystal structures of host Bi0.5Na0.5TiO3 materials. Distortions in the structures and reduction in the optical band gaps of the Bi0.5Na0.5TiO3 materials were possibly due to the random incorporation of Ba and Co cations into host lattice materials. The magnetic properties of the Bi0.5Na0.5TiO3 materials were tuned by controlling the concentrations of BaCoO3−δ as the solid solution. We expect that our work will provide valuable information on current methods for integrating ferromagnetic properties into lead-free ferroelectric materials for the development of multiferroic materials.

COMPARATIVE INVESTIGATION OF THE EFFECT OF TYPE OF DENSITY FUNCTIONAL IN THE DETERMINATION OF GEOMETRICAL PARAMETERS IN A Cu COMPLEX

2013 ◽  
Vol 12 (07) ◽  
pp. 1350066 ◽  
Author(s):  
JABER JAHANBIN SARDROODI ◽  
ALIREZA RASTKAR ◽  
NEGAR RAD YOUSEFNIA ◽  
JAFAR AZAMAT
Keyword(s):  
Density Functional ◽  
Comparative Investigation ◽  
Basis Set ◽  
Basis Sets ◽  
Geometrical Parameters ◽  
Teller Distortion ◽  
Hartree Fock ◽  
Jahn Teller ◽  
Jahn Teller Distortion

The effects of short-range electron correlation, long-range electron exchange, local and nonlocal parts of density, higher order gradients of density, and adding some percentage of Hartree–Fock exchange to the functional on the prediction of geometrical parameters were investigated. A copper complex namely 1,2-bis(1,4,7-triaza-1-cyclononyl) ethane copper (II) with Jahn–Teller distortion in octahedral geometry was used to evaluate the performance of 50 commonly available density functionals. The standard 3-21G basis set was used for all light elements, while pseudo potential LANL2DZ was used for the copper atom. The best bond lengths and bond angles were obtained using M05-2x and OP functionals respectively. Also in order to more accurate survey the performance of B3LYP, we used this functional with two all-electron basis sets (6-31G and 3-21G) and three basis sets involving effective core potentials (LANL2DZ/3-21G, LANL2DZ, and LACVP).

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